JP2918814B2 - Photovoltaic element and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device having high photoelectric conversion efficiency and a method for manufacturing the same.

[0002]

2. Description of the Related Art Photovoltaic elements, which are photoelectric conversion elements for converting sunlight into electric energy, have been widely applied as small power sources for consumer use such as calculators and wristwatches. Has attracted attention as a technology that can be put to practical use as a so-called fossil fuel alternative electric power. A photovoltaic element is a technology that uses the photovoltaic power of a pn junction of a semiconductor. A semiconductor such as silicon absorbs sunlight to generate photocarriers of electrons and holes, and the photocarriers are generated inside the pn junction. It drifts due to the electric field and is taken out.

[0003] Such a method of producing a photovoltaic element is generally performed by using a semiconductor process.
Specifically, a single crystal of valence-controlled silicon is formed into p-type or n-type silicon by a crystal growth method such as a CZ method.
The single crystal is sliced to produce a silicon wafer having a thickness of about 300 μm. Further, a pn junction is formed by forming a layer of a different conductivity type by an appropriate means such as diffusion of a valence electron controlling agent so as to have a conductivity type opposite to the conductivity type of the wafer.

Meanwhile, from the viewpoints of reliability and conversion efficiency, single-crystal silicon is used as a photovoltaic element that has been mainly put into practical use at present. Has a high production cost because it uses a semiconductor process.

Another disadvantage of single-crystal silicon photovoltaic devices is that single-crystal silicon has an indirect transition and therefore has a low light absorption coefficient, and single-crystal photovoltaic devices have at least 50 μm to absorb incident sunlight. The thickness must be increased, and the band gap is about 1.1 eV, which is smaller than 1.5 eV, which is suitable for a photovoltaic device. Therefore, a long wavelength component cannot be used effectively. Even if the production cost is reduced by using polycrystalline silicon, the problem of indirect transition remains, and the thickness of the photovoltaic element cannot be reduced. Polycrystalline silicon also has grain boundaries and other problems.

Further, a large-area wafer cannot be manufactured due to its crystalline nature, and it is difficult to increase the area. If large power is to be taken out, wiring for serializing or parallelizing the unit elements is performed. What you have to do,
When used outdoors, the production cost per unit power generation is lower than that of existing power generation methods because expensive mounting is required to protect the photovoltaic element from mechanical damage caused by various weather conditions. There is a problem that it becomes expensive. Under such circumstances, in promoting the practical use of the photovoltaic element for electric power, cost reduction and enlargement of the area are important technical issues, and various studies have been made.

[0007] Materials such as low-cost materials and materials with high conversion efficiencies have been sought. As materials for such photovoltaic elements, amorphous silicon, amorphous silicon germanium, amorphous Tetrahedral amorphous semiconductor such as porous silicon carbide and II-V such as CdS and Cu ₂ S
Examples thereof include group I and III-V group compound semiconductors such as GaAs and GaAlAs. In particular, a thin-film photovoltaic element using an amorphous semiconductor for the photovoltaic generation layer can produce a film having a larger area than a single-crystal photovoltaic element,
It has advantages such as a thin film thickness and the ability to be deposited on an arbitrary substrate material, and is considered promising.

However, in order to put a photovoltaic element using the above amorphous semiconductor into practical use as a power element,
Improvements in photoelectric conversion efficiency and reliability are issues to be studied.

There are various methods for improving the photoelectric conversion efficiency of a photovoltaic device using an amorphous semiconductor. For example, in the case of a photovoltaic device using a pin-type semiconductor junction, the photoelectric conversion efficiency is increased. In order to improve the efficiency, it is necessary to improve the characteristics of each of the p-type semiconductor layer, the i-type semiconductor layer, the n-type semiconductor layer, the transparent electrode, and the back electrode constituting the photovoltaic element.

As another method for improving the conversion efficiency of a photovoltaic element, the use of a so-called stack cell in which a plurality of photovoltaic elements having a unit element structure are stacked is disclosed in US Pat. No. 2,949,498. Have been. Although a pn junction crystal semiconductor was used in this stack cell, the idea is common to both amorphous and crystalline semiconductors, and the solar spectrum is efficiently absorbed by photovoltaic elements having different band gaps. By increasing the open circuit voltage (V _OC ), the power generation efficiency is improved.

The stack cell is a device in which devices having different band gaps are stacked and the conversion efficiency is improved by efficiently absorbing each part of the spectrum of the sunlight. A so-called top layer located on the light incident side of the stacked devices. The band gap of the so-called bottom layer located below the top layer is designed to be narrower than the band gap of the above.
In response, Hamakawa et al. (Y. Hamakawa, H. Okamoto, and YN
itta “Applied Physics Letters” 35 (1979), P.187)
Reports a so-called cascade-type battery in which amorphous silicon having the same band gap is multi-layered without an insulating layer between photovoltaic elements to increase the open-circuit voltage (V _OC ) of the entire element. In this method, unit elements made of an amorphous silicon material having the same band gap are stacked.

As described above, in the case of a stacked cell, as in the case of a single-layer cell (single cell), in order to improve the photoelectric conversion efficiency, a p-type semiconductor layer and an i-type It is necessary to improve the characteristics of each of the semiconductor layer, the n-type semiconductor layer, the transparent electrode, and the back electrode.

For example, in the case of an i-type semiconductor layer, it is necessary to have a desired band gap depending on the use of a single cell or a stack cell. The level in the gap (local level) is reduced as much as possible, It is important to improve running performance.

[0014] Improvements in the characteristics of the photovoltaic element have been studied by methods other than the method of essentially improving the film quality of the i-type semiconductor layer. As an example, US Pat. No. 4,254,429 discloses a method using a so-called buffer layer for imparting a gradient of a bandwidth at a junction interface between a p-type semiconductor and / or an n-type semiconductor and an i-type semiconductor layer. Patent 4,37
7,723. The purpose of the buffer layer is to provide a large number of levels at the junction interface between a p-type semiconductor or n-type semiconductor formed of amorphous silicon and an i-type semiconductor formed of amorphous silicon germanium due to a difference in lattice constant. Is generated, the open voltage (V _OC ) is improved by using amorphous silicon at the junction interface to eliminate the level and improve the junction and not to impair the carrier traveling property.
Is to improve.

Further, as another method, for example, amorphous silicon germanium is used as the i-type semiconductor layer, and the composition ratio is provided in the intrinsic layer by changing the composition ratio of silicon and germanium to improve the characteristics. There is disclosed a method of providing a so-called gradient layer for improvement. For example, according to US Pat. No. 4,816,082,
The band gap of the i-layer at the portion in contact with the first valence-electron-controlled semiconductor layer on the light incident side is widened, the band gap is gradually narrowed toward the center, and the second valence-electron controlled. A method of gradually increasing the band gap toward a semiconductor layer is disclosed. According to this method, carriers generated by light can be efficiently separated by the action of an internal electric field, and the photoelectric conversion efficiency is improved.

Further, when amorphous silicon or amorphous silicon germanium is used as the i-type semiconductor layer, the i-type semiconductor layer is often slightly n-type.
It has also been studied to improve the hole traveling property by mixing a valence electron controlling agent of the type.

[0017] For a so-called doping layer such as a p-type semiconductor layer or an n-type semiconductor layer, first, it is required that the density of activated acceptors or donors is high and the activation energy is low. Thereby the pin
The diffusion potential (built-in potential) at the time of forming the junction increases, the open-circuit voltage (V _OC ) of the photovoltaic element increases, and the photoelectric conversion efficiency improves.

Next, since the doping layer basically does not contribute to the generation of a photocurrent, it is required that the incidence of light on the i-type semiconductor layer that generates the photocurrent is not hindered as much as possible. Therefore,
In order to reduce light absorption by the doping layer, it is important to widen the optical band gap and reduce the thickness of the doping layer.

Further, it is required that a homo or hetero pin junction is formed between the doping layer and the i-type semiconductor layer, and that the interface level at the junction interface is small.

Examples of the material of the doping layer having the above-mentioned characteristics include a group IV semiconductor alloy material such as Si, SiC, SiN, and SiO. An amorphous or microcrystalline form has been studied. Have been. Above all, since the absorption coefficient is small, the IV having a large optical band gap
Since the group-semiconductor alloy material has a small absorption coefficient and a small activation energy, a microcrystalline or polycrystalline semiconductor material has been considered to be suitable.

However, if such a material is used for the doping layer, the difference in composition and lattice constant between the i-type semiconductor layer and the doping layer necessarily increases, and the difference occurs at the junction interface between the i-type semiconductor layer and the doping layer. The interface state also increases. Further, it becomes difficult to form a buffer layer provided between the i-type semiconductor layer and the doping layer in order to reduce the interface state. That is, in order to smoothly connect the difference in the composition and lattice constant between the i-type semiconductor layer and the doping layer, the buffer layer desirably changes the composition and lattice constant in the buffer layer itself. This is because the larger the difference between the composition and the lattice constant of the semiconductor layer and the doping layer is, the more easily the film quality of the buffer layer itself is deteriorated. It is not possible to improve the open-circuit voltage (V _OC ) or the fill factor (FF) of the photovoltaic element with a buffer layer having poor film quality.

[0022]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention introduces a new buffer layer structure and forming method, thereby realizing low cost, high reliability suitable for practical use, It is another object of the present invention to provide a photovoltaic element having high photoelectric conversion efficiency and a method for manufacturing the same.

[0023]

Means for Solving the Problems As a result of diligent studies on the structure and formation method of the buffer layer, the present inventor has found that a large open-circuit voltage (hereinafter referred to as a large open-circuit voltage) is obtained in a photovoltaic device having a buffer layer having the following structure and a method for manufacturing the same. (V _OC ) and high photoelectric conversion efficiency.

[0024] That is, the manufacturing method of the photovoltaic device of the present invention, the semiconductor junction of the pin-type p-type semiconductor layer and the n-type semiconductor layer two doped layers made of is laminated via the i-type semiconductor layer A method for manufacturing a photovoltaic element, wherein the crystal form of the doping layer D located at least on the i-type semiconductor layer is non-single-crystal, wherein between the i-type semiconductor layer and the doping layer D When the buffer layer B is provided, and the element that expands the band gap of the buffer layer B is γ, after forming the buffer layer B subsequent to the i-type semiconductor layer, before forming the doping layer D, And exposing the surface of the buffer layer B to the plasma containing the γ.

In the first photovoltaic device according to the present invention, two doping layers each composed of a p-type semiconductor layer and an n-type semiconductor layer have an i-type.
Has <br/> a semiconductor junction of stacked pin type through type semiconductor layer, and an optical crystalline form of the doping layer D located on at least the i-type semiconductor layer is non-monocrystalline In the electromotive force element, when the element that expands the band gap of the buffer layer B is γ, the doping layer D
But wherein the formed by the method of producing a photovoltaic element according to claim 1.

According to the second photovoltaic element of the present invention, two doping layers comprising a p-type semiconductor layer and an n-type semiconductor layer have i
In a stack cell type photovoltaic device having a structure in which pin-type semiconductor junctions stacked via a type semiconductor layer are stacked two or more times, when the element that expands the band gap of the buffer layer B is γ , The doping layer D
Wherein at least one layer is formed by the method for manufacturing a photovoltaic element according to claim 1.

The aforementioned buffer layer B contains
The composition ratio of γ is characterized in that it changes over the thickness direction. The buffer layer B described above is characterized in that a part thereof is microcrystallized or polycrystallized in the thickness direction.

[0028]

[Action] (claim 1) wherein the invention according to claim 1, p-type semiconductor layer and n-type of semiconductor layer 2 of the semiconductor junction of the doped layer is pin-type which are stacked through the i-type semiconductor layer And wherein the crystal form of the doping layer D located at least on the i-type semiconductor layer is non-single-crystal, wherein the i-type semiconductor layer and the doping layer D
When the buffer layer B is provided between the layers, and the element that expands the band gap of the buffer layer B is γ, the buffer layer B is formed subsequently to the i-type semiconductor layer, and then the doping layer D is formed. Previously, by exposing the surface of the buffer layer B to the plasma containing γ, the optical band gap of the doping layer D could be increased. In addition, the buffer layer could be formed uniformly over a large area.

[0029] (claim 2) wherein the invention according to claim 2, p-type semiconductor layer and n-type of semiconductor layer 2 of the semiconductor junction of the doped layer is pin-type which are stacked through the i-type semiconductor layer has, and, in the photovoltaic device crystalline form is a non-single-crystal of the doping layer D located on at least the i-type semiconductor layer, a buffer between the doped layer D and the i-type semiconductor layer When the layer B is provided and the element that expands the band gap of the buffer layer B is γ, the buffer layer B
Is formed by the method for manufacturing a photovoltaic element according to claim 1, whereby a difference in composition or a lattice constant between the i-type semiconductor layer and the doping layer D is reduced, and the i-type semiconductor layer and the Since the interface state between the doping layers D has been reduced, the built-in potential of the photovoltaic device has increased, and the open-circuit voltage (V _OC ) and fill factor (FF) of the photovoltaic device have increased. Conversion efficiency improved.

(Claim 3) According to the invention according to claim 3, a pin-type semiconductor junction in which two doping layers composed of a p-type semiconductor layer and an n-type semiconductor layer are stacked via an i- type semiconductor layer is formed. In a stack cell type photovoltaic element having a structure laminated two or more times, a buffer layer B is provided between the i-type semiconductor layer and the doping layer D, and an element for expanding the band gap of the buffer layer B is used. When γ, the buffer layer B
Wherein at least one layer is formed by the method for manufacturing a photovoltaic element according to claim 1, whereby a difference in composition or lattice constant between the i-type semiconductor layer and the doping layer D is reduced, Since the interface state between the i-type semiconductor layer and the doping layer D is reduced, the built-in potential of the pin junction at that portion is increased, and the open voltage (V _OC ) and fill factor of the entire stack type photovoltaic device are increased. (FF) increased and the photoelectric conversion efficiency improved.

(Claim 4) According to the invention of claim 4, the buffer layer B contains
Since the composition ratio of the γ included varies in the film thickness direction, the built-in potential of the photovoltaic element further increases, and the open-circuit voltage (V _OC ) of the photovoltaic element _decreases. The fill factor (FF) increased, and the photoelectric conversion efficiency further improved.

(Claim 5) According to the invention according to claim 5, the buffer layer B comprises:
Since a part is microcrystallized or polycrystallized in the film thickness direction, the built-in potential of the photovoltaic element further increases, and the open voltage (V _OC ) and the fill factor (FF) of the photovoltaic element are increased. .) Was increased, and the photoelectric conversion efficiency was further improved.

Although the detailed mechanism of the above-mentioned operation has not been clarified yet, the following may be considered.

First, a buffer layer is provided between the i-type semiconductor layer and the doping layer. After the buffer layer is formed following the i-type semiconductor layer, before forming the doping layer,
By exposing the surface of the buffer layer to a plasma containing an element that widens the band gap of the buffer layer, an element that widens the band gap is injected into the buffer layer without substantially degrading the film quality of the buffer layer, and the optical band gap is reduced. Increase.

According to this method, when the buffer layer is deposited, a gas containing an element that expands the band gap of the buffer layer is used as a source gas as a part of the mixed gas to decompose the gas, thereby widening the optical band gap. As compared with the case of depositing a buffer layer, a buffer layer with good film quality could be formed with the same optical band gap. This seems to be due to the following reasons.

That is, when a buffer layer having a desired optical band gap is formed by deposition, the quality of the film generally deteriorates as the optical band gap is increased.
That is, the localized level increases, the tail state also increases, the mobility and lifetime of electrons and holes decrease, and the probability of recombination of electrons and holes in the buffer layer increases. With such a buffer layer, the built-in potential of the photovoltaic element cannot be increased.

One of the problems is that a mixed gas of a source gas containing the main constituent elements of the buffer layer and a source gas containing an element for expanding the band gap must be used as the source gas when depositing the buffer layer. It is thought that there is not becoming. In general, the decomposition efficiencies of these two kinds of source gases for the same energy are different, so that it is conceivable that the element that expands the band gap is easily segregated in the film, or a defect is easily generated near the element that expands the band gap. . Conventionally, in order to solve this problem, the type of material gas for the buffer layer has been studied, and a film forming method that devises a method for decomposing the material gas has been studied. There was a problem in terms of damage to the underlying layer.

On the other hand, according to the buffer layer forming method of the present invention, the element for expanding the band gap of the buffer layer is implanted after the buffer layer is deposited.
At the time of deposition, deposition may be performed under optimum deposition conditions that can form a thin film having a high conductivity and a small number of localized levels and tail states. Thereafter, although for injection into the buffer layer an element for expanding the band gap by the plasma treatment, such injection element to expand the band gap by glow discharge flop plasma is conventional used in the crystalline silicon, etc. Unlike ion implantation, the layer to be processed is not damaged by the accelerated ions. In conventional ion implantation, ions are beamed and accelerated, while the energy of ions is high,
Injection with glow discharge plasma, the energy of the injected material is low, because is injected into only a very shallow realm from the surface of the treated layer.

Further, since the two kinds of source gases are not dispersed with the same energy as in the case of deposition, it is easy to find the optimum plasma processing conditions, and the elements which expand the band gap are less likely to segregate in the film. . Therefore, a buffer layer having a small local level and a small tail state and a large optical band gap can be formed without deteriorating the film quality of the buffer layer.

[0040] Therefore, in order to cope with a large doping layer of the optical band gap, even expanding the optical bandgap of the buffer layer, while maintaining the running properties of electrons and holes to maintain good quality , The interface state between the i-type semiconductor layer and the doping layer is reduced, the built-in potential of the photovoltaic device is increased, and the open voltage (V _OC ) and fill factor (FF) of the photovoltaic device are increased. Is considered to have increased.

In order to decompose the above two kinds of source gases and deposit a buffer layer uniformly over a large area, it is necessary to devise a deposition apparatus.
Since the element that enlarges the optical band gap of the buffer layer is later injected, a uniform buffer layer can be easily formed over a large area. Also, it is easy to finely control the depth at which the element for expanding the optical band gap of the buffer layer is injected.

Further, when a buffer layer having a large optical band gap is formed by deposition, a condition under which the energy of ions is large is required, and the underlying layer of the buffer layer, that is, the i-type semiconductor layer is damaged. However, in the case of the present invention, even when a buffer layer having a large optical band gap is formed, a condition in which ion energy is large is not required at the time of deposition, so that the i-type semiconductor layer of the buffer layer may be damaged. Will not give.

Further, according to the present invention, since it is easy to finely control the depth at which the element for expanding the optical band gap of the buffer layer is injected, the conventional method of changing the flow rate of the mixed gas to deposit the mixed gas is used. More easily and precisely, the composition ratio of the element that enlarges the band gap can be changed in the thickness direction of the buffer layer, and the band gap of the buffer layer can be changed in the thickness direction. For example, when the band gap in the vicinity of the doping layer of the buffer layer is particularly increased, the band gap between the doping layer and the i-type semiconductor layer is more smoothly connected than when the band gap of the buffer layer is uniform in the film thickness direction. Therefore, it is considered that the interface state became smaller and the built-in potential of the photovoltaic element became larger. It is also considered that the back diffusion of the photocarriers was reduced due to the inclination of the band gap of the buffer layer, and the open voltage (V _OC ) and fill factor (FF) of the photovoltaic element were increased.

Further, according to the present invention, the vicinity of the surface of the deposited amorphous buffer layer can be microcrystallized or adjusted by adjusting the conditions of the plasma treatment for injecting an element for expanding the band gap of the buffer layer. It can be polycrystallized.

For example, when the doping layer is formed of a microcrystalline material, the vicinity of the surface of the deposited amorphous buffer layer is microcrystallized or polycrystallized so that the microcrystalline or polycrystallized material can be made non-crystalline. The interface state caused by the contact of the crystalline material was reduced, the built-in potential of the photovoltaic element was increased, and the open-circuit voltage (V _OC ) and fill factor (FF) were improved.

This is generally because the doping layer made of a microcrystalline or polycrystalline semiconductor and the i-type semiconductor layer made of an amorphous semiconductor are in contact with each other, so that the p / i interface or the n / i interface is formed.
When an interface is formed, it is considered that an interface level is generated at the p / i interface or the n / i interface. In the above case, the buffer layer made of a microcrystalline or polycrystalline semiconductor and the i-type made of an amorphous semiconductor are used. Between the semiconductors, there is a buffer layer that changes from an amorphous semiconductor to a microcrystalline or polycrystalline semiconductor, so that the crystallinity gradually changes from the doping layer to the i-type semiconductor layer, and the microcrystalline or polycrystalline semiconductor It is considered that the interface state caused by the contact of the amorphous semiconductor was significantly reduced.

[0047]

[Example of embodiment]

(Configuration of Photovoltaic Element) As the configuration of the photovoltaic element of the present invention, there are two types, a single cell type shown in FIG. 1 and a stacked cell type shown in FIG. Below,
The configuration of the photovoltaic element of the present invention and the method of manufacturing the same will be described with reference to the drawings.

FIG. 1 is an example of a schematic sectional view showing a single-cell type photovoltaic device according to the present invention. However,
The present invention is not limited to the photovoltaic element having the configuration shown in FIG. In FIG. 1, 101 is a substrate, 102 is a back electrode, 103 is an n-type semiconductor layer, 104 is an i-type semiconductor layer,
05 is a p-type semiconductor layer, 106 is a transparent electrode, 107 is a collecting electrode, 108 is a buffer layer, and 109 is a buffer layer which is a feature of the present invention. FIG. 1 shows a configuration in which light enters from the p-type semiconductor layer side. In the case of a photovoltaic element having a configuration in which light enters from the n-type semiconductor layer side, 103 is a p-type semiconductor layer and 105 is an n-type semiconductor layer. Layer. Further, FIG. 1 shows a configuration in which light is incident from the opposite side to the substrate. In a photovoltaic element having a configuration in which light is incident from the substrate side, the positions of the transparent electrode and the back electrode are reversed, and 102 is a transparent electrode. 103 may be a p-type semiconductor layer, 105 may be an n-type semiconductor layer, and 106 may be a back surface electrode.

FIG. 2 is an example of a schematic sectional view showing a stacked cell type photovoltaic element according to the present invention. However,
The present invention is not limited to the photovoltaic element having the configuration shown in FIG. The stack cell type photovoltaic element of FIG. 2 has a structure in which three pin junctions are stacked, and 216 is a first pin junction counted from the light incident side, and 215 is a second pin junction.
An n junction 214 is a third pin junction. These three pin junctions are formed on the back surface electrode 202 formed on the substrate 201, and the transparent electrode 212 and the current collecting electrode 213 are formed on the top of the three pin junctions to form a stack. Type photovoltaic element is formed.

The respective pin junctions are formed by n-type semiconductor layers 203, 206, 209, i-type semiconductor layer 204,
207, 210, p-type semiconductor layers 205, 208, 211
Consists of 251 and 252 are buffer layers;
Reference numerals 1, 262 and 263 denote buffer layers which are a feature of the present invention. Further, as in the photovoltaic element of FIG. 1, the arrangement of the doping layers and the electrodes may be switched depending on the incident direction of light.

Hereinafter, the layers constituting the photovoltaic element of the present invention will be described in detail in the order of formation.

(Substrate) The substrate according to the present invention has a semiconductor layer 103 to a thin film having a thickness of about 1 μm on its surface.
Used for depositing 105, 203-211.
Such substrates 101 and 201 have a crystal form (single crystalline or non-single crystalline), an electrical property (conductive or insulating), and an optical property (light-transmitting or non-light-transmitting). It doesn't matter. However, those having little deformation and distortion and having desired strength are preferable.

As the material of the substrate, for example, Fe, N
i, Cr, Al, Mo, Au, Nb, Ta, V, Ti,
Metals such as Pt, Pb or alloys thereof, for example, brass,
A thin plate of stainless steel or the like and its composite, and a film or sheet of a heat-resistant synthetic resin such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polyimide, epoxy, or a combination thereof Composites with glass fiber, carbon fiber, boron fiber, metal fiber, and the like, and thin metal films of different materials and / or SiO ₂ , Si ₃ N ₄ , Al ₂ O _{3 on} the surface of thin plates and resin sheets of these metals , AlN, and other insulating thin films that have been subjected to surface coating by sputtering, vapor deposition, plating, or the like; glass; and ceramics.

When the substrate is electrically conductive such as a metal, it may be used as an electrode for direct current extraction. When the substrate is electrically insulating such as a synthetic resin or the like, the surface on the side where the deposited film is to be formed is coated with Al. , Ag, Pt, Au, Ni, Ti, Mo, W,
Fe, V, Cr, Cu, stainless steel, brass, nichrome,
A so-called simple metal or alloy such as SnO ₂ , In ₂ O ₃ , ZnO, ITO, or a transparent conductive oxide (TCO) is subjected to surface treatment in advance by plating, vapor deposition, sputtering, or the like to form an electrode for extracting current. It is desirable to form it.

Of course, even if the substrate is made of an electrically conductive material such as a metal, the reflectance of long-wavelength light on the substrate surface can be improved, and the mutual interaction of constituent elements between the substrate material and the deposited film can be improved. A different kind of metal layer or the like may be provided on the side of the substrate on which the deposited film is formed for the purpose of preventing diffusion or the like. Further, when the substrate is relatively transparent and a photovoltaic element having a layer structure in which light enters from the side of the substrate is used, a conductive thin film such as the transparent conductive oxide or a metal thin film is previously deposited. It is desirable to form it.

The surface of the substrate may be a so-called smooth surface or a fine uneven surface. In the case of a minute uneven surface, the uneven shape is spherical, conical,
When the shape is a pyramid or the like and the maximum height ( _Rmax ) is preferably 0.05 μm to 2 μm, light reflection on the surface becomes irregular reflection, and the optical path length of the reflected light on the surface increases. Bring.

The shape of the substrate may be a plate having a smooth surface or an uneven surface, a long belt, a cylinder, or the like, depending on the application. The thickness of the substrate may be such that a desired photovoltaic element can be formed. If the photovoltaic element is required to be flexible or light is incident from the side of the substrate, it is possible within the range where the function as the substrate is sufficiently exhibited. It can be as thin as possible. However, the thickness is usually 10 μm or more from the viewpoint of manufacturing and handling of the substrate, mechanical strength and the like.

(Back Electrode, Light Reflecting Layer) The back electrodes 102 and 202 in the present invention are electrodes disposed on the back surface of the semiconductor layer in the light incident direction. Therefore, 102 in FIG.
Or when the substrate 101 is translucent and light is incident from the direction of the substrate, it is disposed at the position 106.

As the material of the back electrode, for example, gold,
Examples include metals such as silver, copper, aluminum, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium, and alloys such as stainless steel. Among them, metals having high reflectance, such as aluminum, copper, silver, and gold, are particularly preferable. In the case of using a metal having a high reflectance, the back electrode can also serve as a light reflecting layer for reflecting light that could not be absorbed by the semiconductor layer again to the semiconductor layer.

The shape of the back electrode may be flat, but it is more preferable that the back electrode has an uneven shape for scattering light.
By having an uneven shape that scatters light, it scatters long-wavelength light that could not be absorbed by the semiconductor layer, extends the optical path length in the semiconductor layer, improves the long-wavelength sensitivity of the photovoltaic element, and increases the short-circuit current. And the photoelectric conversion efficiency can be improved. Uneven shape for scattering the light, it is desirable the height difference of the unevenness of the peaks and valleys is 2.0μm from 0.2μm at R _max.

However, when the substrate also serves as the back electrode,
In some cases, it is not necessary to form the back electrode.

For forming the back electrode, a vapor deposition method, a sputtering method, a plating method, a printing method, or the like is used. When the back electrode is formed to have an uneven shape that scatters light, the formed metal or alloy film is formed by dry etching, wet etching, sandblasting, heating, or the like.
In addition, the above-mentioned metal or alloy can be deposited while heating the substrate to form an uneven shape for scattering light.

The back electrode 102 and the n-type semiconductor layer 10
Although not shown in the figure, a diffusion preventing layer made of conductive zinc oxide or the like may be provided between the first and third layers. The effect of the diffusion preventing layer is not only to prevent the metal element forming the back surface electrode 102 from diffusing into the n-type semiconductor layer, but also to provide a slight resistance value so that the back surface provided with the semiconductor layer interposed therebetween. To prevent short-circuiting caused by defects such as pinholes between the electrode 102 and the transparent electrode 106, and to produce multiple interference by a thin film and confine incident light to a photovoltaic element. Can be.

(Semiconductor Layer) As a material of the semiconductor layer in the present invention, for example, a material using a group IV element such as Si, C, Ge or the like, or a material using a group IV alloy such as SiGe, SiC, SiSn, etc. Used.

Among the above semiconductor materials, semiconductor materials particularly preferably used for the photovoltaic device of the present invention include, for example, a-Si: H (abbreviation for hydrogenated amorphous silicon), a -Si: F, a-Si: H: F, a-SiG
e: H, a-SiGe: F, a-SiGe: H: F, a
And group IV and group IV alloy-based amorphous semiconductor materials such as -SiC: H, a-SiC: F, and a-SiC: H: F.

The semiconductor layer can perform valence electron control and forbidden band width control. Specifically, a source compound containing an element serving as a valence electron controlling agent or a forbidden band width controlling agent when forming a semiconductor layer is used alone, or mixed with the deposited film forming source gas or the diluent gas. What is necessary is just to introduce in a film space.

The semiconductor layer is controlled by valence electrons.
At least a portion thereof is doped p-type and n-type to form at least one set of pin junctions. And
By stacking a plurality of pin junctions, a so-called stack cell configuration is obtained.

As a method of forming a semiconductor layer, a microwave plasma CVD method, an RF plasma CVD method,
Various CVD methods such as VD method, thermal CVD method, MOCVD method, or various evaporation methods such as EB evaporation, MBE, ion plating, ion beam method, sputtering method,
It is formed by a spray method, a printing method, or the like. As a method adopted industrially, a plasma CVD method in which a raw material gas is decomposed by plasma and deposited on a substrate is preferably used. In addition, as the reaction device, a batch type device, a continuous film forming device, or the like can be used as desired.

Hereinafter, a semiconductor layer using a group IV or group IV alloy-based amorphous semiconductor material particularly suitable for the photovoltaic device of the present invention will be described in more detail.

(1) i-type semiconductor layer (intrinsic semiconductor layer) In a photovoltaic device using a group IV and group IV alloy-based amorphous semiconductor material in particular, an i-type layer used for a pin junction is exposed to irradiation light. It is an important layer for generating and transporting carriers.
Slightly p-type and slightly n-type layers can also be used as the i-type layer.

As described above, the group IV and group IV alloy amorphous semiconductor materials contain hydrogen atoms (H, D) or halogen atoms (X), which have an important function.

The hydrogen atoms (H, D) or the halogen atoms (X) contained in the i-type layer work to compensate for dangling bonds in the i-type layer, and the carrier in the i-type layer To improve the product of the mobility and the lifetime. Also p
It has a function of compensating the interface state of each interface of the type layer / i-type layer and the n-type layer / i-type layer, and has an effect of improving the photovoltaic power, the photocurrent and the photoresponsiveness of the photovoltaic element. It is.

The optimum content of hydrogen atoms and / or halogen atoms contained in the i-type layer is 1 to 40 at%. In particular, those in which a large amount of hydrogen atoms and / or halogen atoms are distributed on each interface side of the p-type layer / i-type layer and the n-type layer / i-type layer are mentioned as preferred distribution modes. The content of hydrogen atoms and / or halogen atoms in the above is preferably in a range of 1.1 to 2 times the content in the bulk. Further, it is preferable that the content of hydrogen atoms and / or halogen atoms is changed in accordance with the content of silicon atoms.

In the stack type photovoltaic element, the material of the pin-junction i-type semiconductor layer near the light incident side includes a material having a wide band gap and a p-type material far from the light incident side.
As a material for the in-junction i-type semiconductor layer, a material having a narrow band gap is preferably used.

Amorphous silicon and amorphous silicon germanium are formed by an element for compensating for dangling bonds.
a-Si: H, a-Si: F, a-Si: H: F, a-
SiGe: H, a-SiGe: F, a-SiGe: H:
It is written as F or the like.

Further, the characteristics of the i-type semiconductor layer suitable for the photovoltaic element of the present invention include a hydrogen atom content (C _H ) of 1.0 to 25.0%, an AM of 1.5,
The photoelectric conductivity (σ _p ) under simulated sunlight irradiation of W / cm ² is 1.
0 × 10 ⁻⁷ S / cm or more, dark conductivity (σ _d ) is 1.0 ×
10 ^-9 S / cm or less, the Urbach energy by the constant photocurrent method (CPM) is 55 meV
Hereinafter, those having a localized level density of 10 ¹⁷ / cm ³ or less are preferably used.

(2) P-type semiconductor layer or n-type semiconductor layer (doping layer) The p-type semiconductor layer or n-type semiconductor layer in the present invention is a layer characterizing the photovoltaic device of the present invention. It is an important layer that determines the characteristics.

As a material for the p-type semiconductor layer or the n-type semiconductor layer, a non-single-crystal material is preferably used. The non-single-crystal material of the present invention includes an amorphous material (denoted as a-), a microcrystalline material (denoted as μc-), and a polycrystalline material (po).
ly-).

As an amorphous material (denoted as a−) or a microcrystalline material (denoted as μc−), for example, a-
Si: H, a-Si: HX, a-SiC: H, a-Si
C: HX, a-SiGe: H, a-SiGe: HX, a
-SiGeC: H, a-SiGeC: HX, a-Si
O: H, a-SiO: HX, a-SiN: H, a-Si
N: HX, a-SiON: H, a-SiON: HX, a
—SiOCN: H, a-SiOCN: HX, μc-S
i: H, μc-Si: HX, μc-SiC: H, μc −
SiC: HX, μc-SiO: H, μc-SiO: H
X, μc-SiN: H, μc-SiN: HX, μc-S
iGeC: H, μc-SiGeC: HX, μc-SiO
N: H, μc-SiON: HX, μc-SiOCN:
H, μc-SiOCN: p-type valence electron controlling agent (Group III atom B, Al, Ga, In, T
l) and n-type valence electron controlling agents (atoms P and A of group V in the periodic table)
s, Sb, Bi) are added at a high concentration.

As the polycrystalline material (denoted as poly-), for example, poly-Si: H, poly-Si:
HX, poly-SiC: H, poly-SiC: H
X, poly-SiO: H, poly-SiO: HX,
poly-SiN: H, poly-SiN: HX, po
ly-SiGeC: H, poly-SiGeC: HX,
poly-SiON: H, poly-SiON: HX,
poly-SiOCN: H, poly-SiOCN: H
X, poly-Si, poly-SiC, poly-S
A p-type valence electron controlling agent (Group III atom B, Al, Ga, In, Tl) or n in iO, poly-SiN, etc.
Type valence electron control agents (Group V atoms P, As, S in the periodic table)
b, Bi) at a high concentration.

In particular, the p-type layer or the n-type layer on the light incident side includes:
A crystalline semiconductor layer with low light absorption or an amorphous semiconductor layer with a wide band gap is suitable.

The addition amount of Group III atoms in the periodic table to the p-type layer and the addition amount of Group V atoms in the periodic table to the n-type layer are set to 0.3.
The optimal amount is 1 to 50 at%.

Further, hydrogen atoms (H, D) or halogen atoms contained in the p-type layer or the n-type layer work to compensate for dangling bonds of the p-type layer or the n-type layer, and This is to improve the doping efficiency of the layer. The optimum amount of hydrogen atoms or halogen atoms added to the p-type layer or the n-type layer is 0.1 to 40 at%. Especially p
When the type layer or the n-type layer is crystalline, the optimal amount of hydrogen atom or halogen atom is 0.1 to 8 at%.

Further, those having a large distribution of the content of hydrogen atoms and / or halogen atoms at each interface side of the p-type layer / i-type layer and the n-type layer / i-type layer are mentioned as a preferable distribution form. The content of hydrogen atoms and / or halogen atoms in the vicinity of the interface is preferably in a range of 1.1 to 2 times the content in the bulk.

As described above, by increasing the content of hydrogen atoms or halogen atoms near each interface between the p-type layer / i-type layer and the n-type layer / i-type layer, the defect level and mechanical strain near the interface can be improved. Can be reduced, and the photovoltaic power and the photocurrent of the photovoltaic device of the present invention can be increased.

The p-type layer and the n-type layer of the photovoltaic element preferably have an activation energy of 0.2 eV or less, and most preferably have an activation energy of 0.1 eV or less. The non-resistance is preferably 100 Ωcm or less, and most preferably 1 Ωcm or less. Further, the layer thickness of the p-type layer and the n-type layer is 1 to
50 nm is preferred, and 3 to 10 nm is optimal.

(3) Buffer Layer The buffer layer is a feature of the present invention, and is an important layer that affects the characteristics of the photovoltaic element, like the i-type semiconductor layer and the doping layer.

The buffer layer reduces the interface state which occurs when the composition and crystallization of the material of the doping layer and the i-type semiconductor layer are different, increases the built-in potential of the photovoltaic element, and increases the open-circuit voltage (V _OC ) To increase i
The semiconductor layer is inserted between the type semiconductor layer and the doping layer, and is substantially intrinsic (i-type). Also, a layer of slightly p-type and slightly n-type containing 1% or less of a group III or V element can be used.

The material of the buffer layer of the present invention includes i.
The same material as the mold semiconductor layer and the same material as the doping layer are used. When the material of the i-type semiconductor layer and the material of the doping layer are different, the composition or crystallinity of the buffer layer may gradually change from the material of the i-type semiconductor layer to the material of the doping layer over the thickness direction. .

As in the case of the i-type semiconductor layer or the doping layer, a hydrogen atom (H, D) or a halogen atom which functions to compensate a dangling bond is contained in an amount of 0.1 to 40 at%.
Including. Further, a preferable distribution form includes a large distribution of the content of hydrogen atoms and / or halogen atoms at each interface side with the p-type layer or the n-type layer, and the hydrogen atoms and / or and / or The preferred range of the halogen atom content is 1.1 to 2 times the content in the bulk. As described above, by increasing the content of hydrogen atoms and / or halogen atoms in the vicinity of each interface between the p-type layer / i-type layer and the n-type layer / i-type layer, defect levels and mechanical strain near the interfaces are obtained. Can be reduced.

Further, the characteristics of the buffer layer of the present invention vary depending on the band gap or the crystallinity, but the photoelectric conductivity (σ _p ) under AM1.5, 100 mW / cm ² simulated sunlight irradiation is 1. 0 × 10 ⁻⁷ S / cm or more,
It is preferable to use one having an Urbach energy of 70 meV or less and a localized level density of 10 ¹⁷ / cm ³ or less by a constant photocurrent method (CPM). Also,
The thickness of the buffer layer also depends on the band gap or crystallinity, but is preferably 1 to 100 nm, and 5 to 5 nm.
0 nm is optimal.

Further, the buffer layer, which is a feature of the present invention, is formed by exposing the surface of the buffer layer to a plasma containing an element for expanding the band gap of the buffer layer after the deposition. The plasma processing method will be described later. Examples of the element that enlarges the band gap of the buffer layer include C, O, and N when the main constituent element of the buffer layer is Si.

Further, the buffer layer, which is a feature of the present invention, can change the composition ratio of the element for widening the band gap or change the composition ratio of the element for expanding the band gap depending on the processing conditions of the plasma containing the element for widening the band gap. The part may be microcrystallized or polycrystallized.

(4) Method of Forming Semiconductor Layer A preferred method of forming a group IV and group IV alloy-based amorphous semiconductor layer as a semiconductor layer of the photovoltaic device of the present invention is as follows. , An RF plasma CVD method, a microwave plasma CVD method, or the like, and a plasma CVD method using alternating current or high frequency.

In the microwave plasma CVD method, a material gas such as a raw material gas or a diluent gas is introduced into a deposition chamber (vacuum chamber) which can be reduced in pressure, and the inside pressure of the deposition chamber is kept constant while exhausting the gas by a vacuum exhaust pump. A microwave oscillated by a microwave power source is guided by a waveguide, introduced into the deposition chamber through a dielectric window (alumina ceramics or the like), and generates a plasma of a material gas to decompose the material. This is a method for forming a desired deposited film on a substrate arranged in the above-described manner, and can form a deposited film applicable to a photovoltaic device under a wide range of deposition conditions.

When the semiconductor layer for a photovoltaic device of the present invention is deposited by microwave plasma CVD, the substrate temperature in the deposition chamber is 100 to 450 ° C., and the internal pressure is 0.5 to 30 m.
Torr, microwave power is 0.01 to 1 W / c
m ² and the frequency of the microwave are preferably in the range of 0.1 to 10 GHz.

When the deposition is performed by the RF plasma CVD method, the substrate temperature in the deposition chamber is 100 to 350 ° C., the internal pressure is 0.1 to 10 Torr, and the RF power is 0.001 to 5.
0 W / cm ² and a deposition rate of 0.01 to 3 nm / sec are preferable conditions.

The source gas suitable for depositing the group IV and group IV alloy-based amorphous semiconductor layer suitable for the photovoltaic device of the present invention includes a gasizable compound containing silicon atoms,
A gasizable compound containing a germanium atom, a gasifiable compound containing a carbon atom, a gasifiable compound containing a nitrogen atom, a gasifiable compound containing an oxygen atom, and the like, and a mixed gas of the compound can be given. it can.

Specifically, gasification containing silicon atoms
As the compound to be obtained, a chain or cyclic silane compound is used.
And specifically, for example, SiH_Four, Si_TwoH₆, Si
F_Four, SiFH_Three, SiF_TwoH_Two, SiF_ThreeH, Si_ThreeH₈,
SiD_Four, SiHD_Three, SiH_TwoD_Two, SiH_ThreeD, SiF
D_Three, SiF_TwoD_Two, Si_TwoD_ThreeH_Three, (SiF_Two)_Five, (Si
F_Two)₆, (SiF_Two)_Four, Si_TwoF₆, Si_ThreeF₈, Si_TwoH_Two
F_Four, Si_TwoH_ThreeF_Three, SiCl_Four, (SiCl_Two)_Five, Si
Br_Four, (SiBr_Two)_Five, Si_TwoCl₆, SiHCl _Three, S
iH_TwoBr_Two, SiH_TwoCl_Two, Si_TwoCl_ThreeF_ThreeSuch as gas
Those that are in a state or that can be easily gasified are included.

Specifically, a gas containing a germanium atom
The compound which can be converted to is GeH_Four, GeD_Four, GeF_Four,
GeFH_Three, GeF_TwoH_Two, GeF_ThreeH, GeHD_Three, Ge
H_TwoD _Two, GeH_ThreeD, Ge_TwoH₆, Ge_TwoD₆Etc.
You.

Specifically, gasification containing a carbon atom can be performed.
As the compound, CH_Four, CD_Four, C _nH_{2n + 2}(N is integer
Number), C_nH_2n(N is an integer), C_TwoH_Two, C₆H₆, CO_Two,
CO and the like.

As the nitrogen-containing gas, N ₂ , NH ₃ , ND
₃ , NO, NO ₂ and N ₂ O. Examples of the oxygen-containing gas include O ₂ , CO, CO ₂ , NO, NO ₂ , N ₂ O, and CH.
₃ CH ₂ OH, CH ₃ OH and the like.

As a substance introduced into the p-type layer or the n-type layer for controlling valence electrons, there can be mentioned a Group III element and a Group V atom of the periodic table.

As the starting material for introducing a group III atom effectively, specifically, for introducing a boron atom, B ₂ H ₆ , B ₄ H ₁₀ , B ₅ H ₉ , B ₅ H ₁₁ , B
_{6 H 1 0, B 6 H} 12, B 6 borohydride of H _14, etc., BF _3, B
Examples thereof include boron halides such as Cl ₃ .
In addition, AlCl ₃ , GaCl ₃ , InCl ₃ , TIC
l ₃ and the like can also be mentioned. Particularly, B ₂ H ₆ and BF ₃ are suitable.

Effectively used as a starting material for introducing a group V atom is, specifically, P for introducing a phosphorus atom.
Phosphorus hydride such as H ₃ , P ₂ H ₄ , PH ₄ I, PF ₃ , PF ₅ ,
Phosphorus halides such as PCl ₃ , PCl ₅ , PBr ₃ , PBr ₅ , and PI ₃ are mentioned. In addition, AsH ₃ , AsF ₃ ,
AsCl ₃ , AsBr ₃ , AsF ₅ , SbH ₃ , SbF ₃ ,
SbF ₅ , SbCl ₃ , SbCl ₅ , BiH ₃ , BiC
l _3, BiBr _3, and the like can also be mentioned. Especially PH ₃ ,
PF ₃ is suitable.

Further, the compound capable of being gasified is H ₂ , H
The gas may be appropriately diluted with a gas such as e, Ne, Ar, Xe, or Kr and introduced into the deposition chamber.

Particularly, a microcrystalline or polycrystalline semiconductor or a-S
When depositing a layer having a small light absorption or a wide band gap such as iC: H, the source gas is diluted 2 to 100 times with hydrogen gas, and a relatively high microwave power or RF power is introduced. Is preferred.

(5) Method of Plasma Treatment of Buffer Layer Hereinafter, a method of plasma treatment of the buffer layer, which is a feature of the present invention, will be described.

In the plasma treatment of the buffer layer, a material gas, a diluent gas, or the like is introduced into a deposition chamber (vacuum chamber) that can be decompressed, and the internal pressure of the deposition chamber is kept constant while evacuating by a vacuum pump. Glow discharge plasma that generates a plasma of a material gas by applying AC or high frequency is used. As the frequency, various frequencies from DC to microwaves of about 10 GHz can be used.

The material gas contains carbon, oxygen, nitrogen, etc., which are elements for expanding the band gap of the buffer layer of the photovoltaic device of the present invention.

Specific examples of the gasizable compound containing a carbon atom include CH ₄ , CD ₄ , C _n H _{2n + 2} (n is an integer), C _n H _2n (n is an integer), C ₂ H ₂ , C ₆ H ₆ , CO ₂ ,
CO and the like. N ₂ , N
H ₃ , ND ₃ , NO, NO ₂ , and N ₂ O are mentioned.

The oxygen-containing gases include O ₂ , CO, CO ₂ ,
NO, NO ₂ , N ₂ O, CH ₃ CH ₂ OH, CH ₃ OH and the like. Further, as the diluent gas, H ₂ , He, N
Gases such as e, Ar, Xe, and Kr can be used.

Further, since a semiconductor layer is not deposited, a source gas suitable for depositing a group IV or group IV alloy amorphous semiconductor layer may not be used. Also, when a source gas suitable for depositing the group IV and group IV alloy-based amorphous semiconductor layers is used, the pressure of the gas for generating plasma is set lower than that under normal deposition conditions so that a deposition reaction does not occur. It is desirable to lower the voltage, increase the DC voltage or AC power applied to the plasma, or increase the dilution ratio with the dilution gas.

As described above, the implantation of the element for expanding the band gap of the buffer layer by the glow discharge plasma is completely different from the conventional ion implantation used for crystalline silicon or the like. In the conventional ion implantation, the ions are accelerated in a beam form, and the energy of the ions is high. On the other hand, the implantation by the glow discharge plasma has a low energy of the implanted material and is extremely shallow from the surface of the deposited layer. It is implanted only up to the region. Further, delicate control of the implantation depth is easy, and uniform implantation over a large area can be easily performed. Further, since the surface of the i-type semiconductor layer is not damaged by the accelerated ions, a buffer layer with few localized levels can be formed without deteriorating the film quality of the deposited layer. Therefore, the buffer layer can be formed uniformly over a large area with good film quality.

Suitable conditions for the glow discharge plasma vary depending on the material of the buffer layer to be processed, the type of material gas, the frequency of the power applied to the plasma, and the like. Indoor substrate temperature is 100-450 ° C, internal pressure is 0.5-30mTo
rr, the microwave power is preferably 0.01 to 1 W / cm ² , and the microwave frequency is preferably 0.1 to 10 GHz. DC, AC, LF or R
In the case of F plasma, the substrate temperature in the deposition chamber is 100 to 35.
0 ° C., internal pressure 0.1 to 10 Torr, power 0.01
５5.0 W / cm ² is a preferable condition.

Further, depending on the conditions of the glow discharge plasma, it is possible to control the depth and concentration of the element for expanding the band gap of the buffer layer, and to change the crystallinity near the surface of the buffer layer. It is. The control method is described below.

First, one is to control the pressure of the material gas. By lowering the pressure of the gas, the injection efficiency of the element that enlarges the band gap of the buffer layer increases. Although the details of this mechanism have not been clarified, it is considered that when the gas pressure is reduced, the self-bias of the electrode is increased, so that the energy of positive ions decomposed in the plasma state is increased. It is also conceivable that the mean free path of positive ions is increasing.

It is also to control the DC voltage or AC power applied to the plasma. By increasing the DC voltage or the AC power, the injection efficiency of the element that enlarges the band gap of the buffer layer increases. Although the details of this mechanism have not been clarified, it is considered that when the DC voltage or the AC power is increased, the plasma potential is increased, and the energy of the positive ions decomposed in the plasma state is increased.

Further, a special effect is produced by the fact that hydrogen is contained in the mixed gas of the plasma processing. In other words, first, hydrogen ions or radicals are generated by the plasma, but the hydrogen ions or radicals have an etching action, so that the mixed gas of the aforementioned group IV and group IV alloy-based amorphous semiconductor layer is added to the mixed gas. Even when a source gas suitable for deposition is included, by increasing the dilution ratio with hydrogen gas, deposition of the source gas can be suppressed, and an element for expanding the band gap of the buffer layer can be implanted. .

Second, by implanting hydrogen atoms as well as the element for expanding the band gap into the buffer layer, dangling bonds (dangling bonds) of the buffer layer caused by the implantation of the element for expanding the band gap are implanted. ), And can increase the activation rate of the acceptor or the donor.

Third, by implanting hydrogen atoms near the surface of the buffer layer, the band gap of the buffer layer near the surface is further increased, and light absorption in the buffer layer is reduced.

Fourth, the crystallinity near the surface of the buffer layer can be increased by increasing the dilution ratio with hydrogen gas and, at the same time, increasing the DC voltage or AC power applied to the plasma.

(Transparent Electrode) The transparent electrode 10 of the present invention
Numeral 6 has both a role as an electrode on the light incident side for transmitting light and a role as an anti-reflection film by optimizing the film thickness. The transparent electrode 106 is required to have a high transmittance in a wavelength region where the semiconductor layer can absorb light and a low resistivity. Preferably, the transmittance at 550 nm is at least 80%, more preferably at least 85%. The resistivity is preferably 5 × 10
^-3 Ωcm or less, more preferably 1 × 10 ⁻³ Ωcm or less. As the material, for example, I
n ₂ O ₃ , SnO ₂ , ITO (In ₂ O ₃ + SnO ₂ ), Zn
O, CdO, Cd ₂ SnO ₄ , TiO ₂ , Ta ₂ O ₅ , Bi ₂
A conductive oxide such as O ₃ , MoO ₃ , and Na _x WO _3, or a mixture thereof is preferably used. Further, an element (dopant) that changes the conductivity may be added to these compounds.

As an element (dopant) for changing the conductivity, for example, when the transparent electrode 107 is ZnO,
Al, In, B, Ga, Si, F, etc., In the case of In ₂ O ₃ , Sn, F, Te, Ti, Sb, Pb, etc., and in the case of SnO ₂ , F, Sb, P, As, In, T
1, Te, W, Cl, Br, I, etc. are preferably used.

As the method for forming the transparent electrode 106, a vapor deposition method, a CVD method, a spray method, a spin-on method, a dipping method, or the like is suitably used.

(Current Collecting Electrode) The current collecting electrode 10 of the present invention
7 is formed on a part of the transparent electrode 106 as necessary when the resistivity of the transparent electrode 106 cannot be sufficiently reduced;
It functions to lower the resistivity of the electrode and lower the series resistance of the photovoltaic element. As the material, for example, a metal such as gold, silver, copper, aluminum, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, zirconium, or an alloy such as stainless steel, or a powdered metal is used. Conductive paste and the like.
The shape is formed, for example, in a branch shape as shown in FIG. 3 so as not to block incident light to the semiconductor layer as much as possible.

Also, in the entire area of the photovoltaic device,
The area occupied by the collecting electrode is preferably 15% or less, more preferably 10% or less, and most preferably 5% or less.

Further, a pattern of the collecting electrode is formed by using a mask, and the forming method includes a vapor deposition method, a sputtering method,
A plating method, a printing method, or the like is used.

When a photovoltaic device (module or panel) having a desired output voltage and output current is manufactured using the photovoltaic device of the present invention, the photovoltaic devices of the present invention are connected in series or in series. They are connected in parallel, protective layers are formed on the front and back surfaces, and output output electrodes and the like are attached. When the photovoltaic elements of the present invention are connected in series, a diode for preventing backflow may be incorporated.

[0130]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a photovoltaic element made of a non-single-crystal silicon-based semiconductor material will be described in detail, but the present invention is not limited to this.

Example 1 In this example, the single-cell type photovoltaic element shown in FIG. 1 was produced using the deposition apparatus shown in FIG. In this example, when the element that enlarges the band gap of the buffer layer B is γ, after forming the buffer layer B following the i-type semiconductor layer, before forming the doping layer D, the buffer layer The case where the surface of B was exposed to the plasma containing γ was examined.

In the following, the method of making the same will be described according to the procedure. (1) A stainless steel support 101 having a thickness of 0.5 mm and a size of 50 × 50 mm ² was subjected to ultrasonic cleaning with acetone and isopropanol, and dried with warm air. Thereafter, a 0.3 μm-thick Ag light-reflecting layer and a 350 μm-thickness
A reflection enhancement layer of ZnO having a layer thickness of 1.0 μm was formed at a temperature of 0 ° C. to form a back electrode 102. After these steps, the substrate 4
90.

(2) Using the deposition apparatus 400, the substrate 49
On each of the semiconductor layers, a semiconductor layer was formed. The deposition apparatus 400 can perform both the microwave plasma CVD method and the RF plasma CVD method.

A raw material gas cylinder (not shown) is connected to this deposition apparatus through a gas introduction pipe. The raw material gas cylinders were all purified to ultra-high purity, and were SiH ₄ gas cylinders, SiF ₄ gas cylinders, SiH ₄ / H ₂ (SiH ₄ gas diluted with H ₂ , dilution degree SiH ₄ : 10%) gas cylinders, CH ₄ Gas cylinder, C ₂ H ₂ gas cylinder, GeH ₄ gas cylinder, GeF ₄ gas cylinder, Si ₂ H ₆ gas cylinder, P
H ₃ / H ₂ (dilution: 2%) gas cylinder, BF ₃ / H ₂ (dilution: 1%) gas cylinder, H ₂ gas cylinder, He gas cylinder, NH ₃ gas cylinder, O ₂ / He (dilution degree: 1%) A gas cylinder and a NO gas cylinder were connected.

(3) The substrate 490 is placed in the load chamber 40
The load chamber 401 was evacuated by a vacuum evacuation pump (not shown) until the pressure reached about 1 × 10 ⁻⁵ Torr.

(4) The gate valve 406 was opened and transferred into the transfer chamber 402 and the deposition chamber 417, which were previously evacuated by a vacuum exhaust pump (not shown). The back surface of the substrate 490 is heated by a substrate heating heater 410.
Then, the inside of the deposition chamber 417 was evacuated by a vacuum evacuation pump (not shown) until the pressure reached about 1 × 10 ⁻⁵ Torr. Preparation for film formation was completed as described above.

(5) To form an n-type layer made of a-Si (an n-type semiconductor layer formed by RF plasma CVD), H ₂ gas is introduced into the deposition chamber 417 through a gas introduction pipe 429. The valve (not shown) was opened so that the H ₂ gas became 200 sccm, and adjustment was performed with a mass controller (not shown). The conductance valve (not shown) was adjusted so that the pressure in the deposition chamber 417 became 1.1 Torr.

(6) The substrate heating heater 410 is set so that the temperature of the substrate 490 becomes 350 ° C. When the substrate temperature becomes stable, the SiH ₄ gas and PH ₃ / H ₂ gas are not introduced into the deposition chamber 417. The gas was introduced through the gas introduction pipe 429 by operating the illustrated valve. At this time, the mass flow controller was adjusted so that the SiH ₄ gas was ₂ sccm, the H ₂ gas was 50 sccm, and the PH ₃ / H ₂ gas was 0.5 sccm, and the pressure in the deposition chamber 417 was 1.1.
It was adjusted to Torr.

(7) The power of the RF high frequency (hereinafter abbreviated as “RF”) power supply 422 is set to 0.005 W / cm ² , and RF power is introduced into the plasma forming cup 420.
Glow discharge was generated to start formation of an n-type layer on the substrate. When an n-type layer having a thickness of 10 nm was formed, RF power was turned off to stop glow discharge, and formation of the n-type layer 103 was completed.

(8) SiH into the deposition chamber 417
_After stopping the inflow of ₄ gases, PH ₃ / H ₂ , and continuing the flow of H ₂ gas into the deposition chamber for 5 minutes, stopping the inflow of H ₂ , and vacuuming the deposition chamber and the gas pipe to 1 × 10 ⁻⁵ Torr. Exhausted.

(9) i-type layer 104 made of a-Si: H
Was formed by a microwave plasma CVD method. First, the gate valve 407 is opened into the transfer chamber 403 and the i-type layer deposition chamber 418 evacuated by a vacuum exhaust pump (not shown), and the substrate 490 is opened.
Was transported. The back surface of the substrate 490 is heated with the heater 4 for heating the substrate.
11 and heated, and the pressure in the i-type layer deposition chamber 418 was set to about 1 × 10 ⁻⁵ T by a vacuum exhaust pump (not shown).
The chamber was evacuated to orr.

(10) To form an i-type layer, the substrate 49
Substrate heating heater 4 so that the temperature of
11 was set, and when the substrate was sufficiently heated, a valve (not shown) was gradually opened to allow SiH ₄ gas and H ₂ gas to flow into the i-type layer deposition chamber 418 through the gas introduction pipe 449. At this time, the mass controllers (not shown) were adjusted so that the SiH ₄ gas was 50 sccm and the H ₂ gas was 100 sccm. i-type layer deposition chamber 418
The internal pressure of the conductance valve (not shown) was adjusted so that the internal pressure became 5 mTorr.

(11) The RF power supply 424 is set at 0.2 W / cm
Set to ² and applied to bias bar 428. Thereafter, the power of a microwave power supply (not shown) is set to 0.1 W / cm ² , and microwave power is introduced into the i-type layer deposition chamber 418 through the microwave introduction waveguide 426 and the microwave introduction window 425. Then, a glow discharge is generated, and the shutter 427 is opened to start forming an i-type layer on the n-type layer. When an i-type layer having a thickness of 0.3 μm is formed, the microwave glow discharge is stopped, and a bias power supply is turned off. The output of 424 was cut off, and the formation of the i-type layer 104 was completed.

(12) The valve (not shown) was closed to stop the flow of the SiH ₄ gas into the i-type layer deposition chamber 418, and the H ₂ gas continued to flow into the i-type layer deposition chamber 418 for 2 minutes. (13) a- having a larger band gap than the i-type layer.
The buffer layer 109 made of Si: H was formed by a microwave plasma CVD method.

(14) To form the buffer layer 109, a buffer layer 10 having a thickness of 25 nm is formed in the same manner as the i-type layer 104 except that the temperature of the substrate 490 is set to 280 ° C.
9 was formed. (15) After the formation of the buffer layer 109, the valve (not shown) is closed, and SiH ₄ is introduced into the i-type layer deposition chamber 418.
Stop the inflow of gas, i-type layer deposition chamber 418 for 2 minutes
The flow of H ₂ gas was continued. (16) The valve (not shown) was closed, and the inside of the i-type layer deposition chamber 418 and the inside of the gas pipe were evacuated to 1 × 10 ⁻⁵ Torr.

(17) Before forming the doping layer on the i-type semiconductor layer, CH _{4 is used} to expose the surface of the buffer layer B to a plasma containing an element (γ) for expanding the band gap of the buffer layer B. Gas and He gas are introduced into the deposition chamber 418 by operating a valve (not shown).
9 introduced. At this time, CH ₄ gas is supplied at 10 scc.
The m and He gases were adjusted by a mass flow controller to 300 sccm, and the pressure in the deposition chamber 418 was adjusted to 0.5 Torr. Substrate 490
Is maintained at 280 ° C., and the power of the RF power supply 424 is set to 0.
At a setting of 08 W / cm ² , RF power was introduced into the bias rod 428 to generate glow discharge, and the wafer was exposed to the above-mentioned plasma containing γ for 600 seconds to form the buffer layer 109 of the present invention composed of a-SiC: H. did.

(18) After the formation of the buffer layer 109, the valve (not shown) is closed to stop the flow of the CH ₄ gas and the He gas into the i-type layer deposition chamber 418, for 2 minutes.
After continuing the flow of H ₂ gas into the i-type layer deposition chamber 418, the valve (not shown) is closed, and the i-type layer deposition chamber 4 is closed.
The inside of 18 and the inside of the gas pipe were evacuated to 1 × 10 ⁻⁵ Torr. (19) A p-type semiconductor layer 105 made of μc-Si (microcrystalline silicon) was formed by the following procedure.

(20) The gate valve 408 was opened and the substrate 490 was transferred into the transfer chamber 404 and the p-type layer deposition chamber 419 that were previously evacuated by a vacuum pump (not shown). The back surface of the substrate 490 was heated by being brought into close contact with a heater 412 for heating the substrate, and the inside of the p-type layer deposition chamber 419 was evacuated by a vacuum exhaust pump (not shown) until the pressure became about 1 × 10 ⁻⁵ Torr.

(21) The temperature of the substrate 490 reaches 230 ° C.
The substrate heating heater 412 is set to
When is stable, H_TwoGas, SiH_Four/ H_TwoGas, B
F_Three/ H _TwoA gas (not shown) is introduced into the deposition chamber 419.
The gas was introduced through the gas introduction pipe 469 by manipulating the gas. this
At this time, operating a valve (not shown)_TwoGas is 50scc
m, SiH_Four/ H_Two0.5 sccm gas, BF_Three/ H_TwoMoth
Mass flow control so that the flow rate is 0.5 sccm
And the pressure in the deposition chamber 419 is 2 To
opening of a conductance valve (not shown) so as to be rr
Was adjusted.

(22) The power of the RF power supply 423 is set to 0.15
W / cm ² , and R was added to the plasma forming cup 421.
F power was introduced to generate glow discharge, the formation of a p-type layer of μc-Si was started, and when the layer thickness was 7 nm, the RF power was turned off to stop the glow discharge and the formation was completed.

(23) The valve (not shown) is closed, and SiH ₄ / H ₂ gas and BF ₃ /
Stopping the flow of H ₂ gas for 3 minutes, after which continued to flow H ₂ gas into the p-type layer deposition chamber 419, stopping the inflow of H ₂ closes the valve (not shown), p-type layer deposition chamber 41
The inside of 9 and the gas pipe were evacuated to 1 × 10 ⁻⁵ Torr.

(24) The gate valve 409 is opened into the unload chamber 405 that has been evacuated by a vacuum exhaust pump (not shown) to transfer the substrate 490, and the leak valve (not shown) is opened to open the unload chamber 405. Leaked. (25) On the p-type layer, as the transparent conductive layer 106, a layer thickness of 7
0 nm of ITO was vacuum deposited by a vacuum deposition method.

(26) A mask having a comb-shaped hole is placed on the transparent conductive layer 106, and Cr (40 nm) / Ag (100
0 nm) / Cr (40 nm) and the comb-shaped current collecting electrode 107 of FIG. 3 was vacuum-deposited by a vacuum deposition method. Thus, the creation of the photovoltaic element has been completed. This photovoltaic element is called (SC Ex. 1).

(Comparative Example 1-1) In this example, before forming the doping layer on the i-type semiconductor layer, the surface of the buffer layer B was not exposed to the plasma containing γ (implementation). Different from Example 1).

The other points were the same as in (Example 1). The photovoltaic element produced in this example was called (SC ratio 1-1).

In the following, (Example 1) and (Comparative Example 1-
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 1 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 1-1) (SC actual 1). (FF).

[0159]

[Table 1] From Table 1, it was found that the photovoltaic element of (SC Ex. 1) was superior in open-circuit voltage (V _OC ), fill factor (FF), and photoelectric conversion efficiency (η). .

(Comparative Example 1-2) In this example, the following three points
(Example 1) is different. (A) When forming the buffer layer 109, use SiH_FourMoth
Is 50 sccm, C_TwoH _TwoGas is 35sccm, H_TwoMoth
Mass flow control so that the flow rate is 120 sccm
Pressure in the deposition chamber is 5 mTorr
It was adjusted to be.

(B) A buffer layer of a-SiC: H having a thickness of 25 nm was formed by microwave plasma CVD. (C) A step of exposing the surface of the buffer layer B to the plasma containing γ before forming the doping layer on the i-type semiconductor layer was omitted.

The other points were the same as in (Example 1). The photovoltaic element produced in this example was called (SC ratio 1-2).

Hereinafter, (Example 1) and (Comparative Example 1-
An evaluation test performed on each of the six photovoltaic elements obtained in 2) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 2 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 1-1) (SC actual 1). (FF).

[0166]

[Table 2] From Table 2, it can be seen that the photovoltaic element of ( _SC Ex. 1) is superior in open-circuit voltage (V _OC ), short-circuit current (J _SC ), fill factor (FF), and photoelectric conversion efficiency (η). It turned out to be excellent.

Also, in order to observe the variation in the characteristics within the substrate, when depositing ITO, a mask having a hole of 0.25 cm ² was used, so that 25 light beams divided on one substrate were used. An electromotive element was created. Table 3 shows the results of examining the open-circuit voltage (V _OC ) and the fill factor (FF) in the substrate for such a sample. However, the maximum value on the same substrate was set to 1.

[0168]

[Table 3] From Table 3, it was found that the photovoltaic element of (SC Ex. 1) had smaller variations in the substrate, and thus improved the uniformity of the photoelectric conversion characteristics.

Example 2 In this example, as shown below, conditions for forming an n-type layer made of μc-Si, conditions for exposing the surface of a buffer layer to plasma, and conditions for forming an MWi-type layer made of a-SiGe And the conditions for forming the p-type layer made of a-SiC are different from those of the first embodiment.

(A) Conditions for Forming N-Type Layer In order to form an n-type layer made of μc-Si (an n-type semiconductor layer formed by RF plasma CVD), a first embodiment is described.
Similarly to the above, the substrate 490 is transferred into the deposition chamber 417, and the SiH ₄ / H ₂ gas is 4 sccm and the H ₂ gas is 100 sccm.
The mass flow controller was adjusted so that the sccm and PH ₃ / H ₂ gas became 1 sccm, and the pressure in the deposition chamber was adjusted so as to be 0.5 Torr.

The substrate heating heater was set so that the substrate temperature became 380 ° C., and when the substrate temperature was stabilized,
The power of the RF power source was set to 0.04 W / cm ² , RF power was introduced into the plasma forming cup to cause glow discharge, and the formation of an n-type layer on the substrate was started. A layer was formed.

Next, the buffer layer 10 made of a-Si
No. 8 was produced by an RF plasma CVD method.

In order to form the buffer layer 108, as in the first embodiment, the substrate 490 is transferred to the deposition chamber 418, and the substrate heating heater 411 is set so that the temperature of the substrate 490 becomes 330 ° C. Is heated sufficiently, the valve (not shown) is gradually opened, and SiH ₄ gas,
H ₂ gas was introduced into the i-type layer deposition chamber 418 through the gas introduction pipe 449. At this time, the mass flow controllers (not shown) were adjusted so that the SiH ₄ gas was 10 sccm and the H ₂ gas was 300 sccm.

The opening of the conductance valve (not shown) was adjusted so that the pressure in the i-type layer deposition chamber 418 became 1.1 Torr.

The power of the RF power supply 424 is set to 0.01 W / cm
^It was set to ² and applied to the bias rod 428 to cause glow discharge to start the formation of the buffer layer 108 on the substrate, forming a 10 nm thick buffer layer.

(B) Conditions for Forming MWi-Type Layer The MWi-type layer (i-type semiconductor layer formed by the microwave CVD method) was made of a-SiGe. In order to form an MWi-type layer, a substrate heating heater is set so that the substrate temperature becomes 380 ° C., and when the substrate is sufficiently heated, a valve (not shown) is gradually opened, and a SiH ₄ gas, a GeH ₄ gas , H
_Two gases were introduced into the i-type layer deposition chamber through the gas introduction pipe. At this time, the SiH ₄ gas is 50 sccm, G
The mass flow controllers (not shown) adjusted the eH ₄ gas to 35 sccm and the H ₂ gas to 120 sccm. The pressure in the i-type layer deposition chamber is 6 mTo
The opening of the conductance valve (not shown) was adjusted so as to be rr. Next, the RF power was set to 0.2 W / cm ² and applied to the bias bar. Thereafter, the power of a microwave power supply (not shown) was set to 0.1 W / cm ² , microwave power was introduced into the i-type layer deposition chamber, glow discharge was generated, and the shutter was opened to place the RF power on the RFi-type layer. MW
The formation of the i-type layer was started. When the i-type layer having a thickness of 0.1 μm was formed, the microwave glow discharge was stopped, and the formation of the MWi-type layer was completed.

(C) Conditions for Forming Buffer Layer 109 In the same manner as in Example 1, a buffer layer made of a-Si was formed to a thickness of 25 nm.

Before forming the p-type doping layer on the i-type semiconductor layer, CH _{4 is used} to expose the surface of the buffer layer B to plasma containing an element (γ) for expanding the band gap of the buffer layer B. Gas and He gas are introduced into the deposition chamber 418 by operating a valve (not shown).
Introduced through. In addition, BF ₃ gas diluted to 1000 ppm with H ₂ was also introduced in order to inject boron slightly into the buffer layer. At this time, CH ₄ gas is
The BF ₃ gas diluted to 0 sccm and 1000 ppm with H ₂ was adjusted with a mass flow controller to 1 sccm and the He gas to 300 sccm, and the deposition chamber 4 was adjusted.
The pressure in 18 was adjusted to be 1.0 Torr.
The temperature of the substrate 490 was maintained at 280 ° C., the power of the RF power source 424 was set at 0.06 W / cm ² ,
RF power is introduced into the γ 8 to generate a glow discharge,
The buffer layer 109 of the present invention was formed by exposing the deposited buffer layer made of a-Si to a-SiC: H only near the surface for 150 seconds.

(D) Conditions for forming p-type semiconductor layer 105 A p-type semiconductor layer 105 made of a-SiC was formed. As in the first embodiment, the substrate 4 is transferred to the p-type layer deposition chamber 419.
90, the substrate heating heater 412 was set so that the substrate temperature became 230 ° C., and when the substrate temperature was stabilized, H ₂ gas was 50 sccm and SiH ₄ gas was 2 sccc.
m, ₂ sccm of C ₂ H ₂ gas, 4 sc of BF ₃ / H ₂ gas
cm with a mass flow controller,
The opening of a conductance valve (not shown) was adjusted so that the pressure in the deposition chamber 419 was 2.0 Torr. The power of the RF power supply 423 was set to 0.03 W / cm ² , and RF power was introduced into the plasma forming cup 421,
A glow discharge is generated to start formation of a p-type layer made of a-SiC. When a layer thickness of 10 nm is formed, RF power is turned off to stop glow discharge and form p-type semiconductor layer 105 made of a-SiC. Finished.

The other points were the same as in (Example 1). The photovoltaic element produced in this example was called (SC Ex. 2).

(Comparative Example 2-1) In this example, before forming the doping layer on the i-type semiconductor layer, the surface of the buffer layer B was not exposed to the plasma containing γ (implementation). Different from Example 2).

The other points were the same as in (Example 2). The photovoltaic element produced in this example was called (SC ratio 2-1).

Hereinafter, (Example 2) and (Comparative Example 2)
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 4 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 2-1) (SC actual 2). (FF).

[0186]

[Table 4] From Table 4, it was found that the photovoltaic element of (SC Ex. 2) was superior in open-circuit voltage (V _OC ), fill factor (FF), and photoelectric conversion efficiency (η). .

Example 3 In this example, as shown below, the conditions for forming an n-type layer made of a-SiC,
The conditions for forming the MWi-type layer made of, the conditions for forming the p-type semiconductor layer made of μc-SiCN, and the conditions for forming the buffer layer are different from those of the first embodiment.

(A) Conditions for forming n-type layer To form an n-type layer made of a-SiC (an n-type semiconductor layer formed by RF plasma CVD), use SiH ₄
/ H ₂ gas ₂ sccm, C ₂ H ₂ gas ₂ sccm, H ₂
The mass flow controller was used to adjust the gas to 50 sccm and the PH ₃ / H ₂ gas to 1 sccm, and the pressure in the deposition chamber 417 was adjusted to 1.1 Torr. The substrate heating heater is set so that the substrate temperature becomes 380 ° C., and when the substrate temperature is stabilized, RF
The power of the power supply was set to 0.03 W / cm ² , RF power was introduced into the plasma forming cup to cause glow discharge, and the formation of an n-type layer on the substrate was started.
A mold layer was formed.

(B) Conditions for Forming MWi-Type Layer The MWi-type layer was made of a-SiC. Create MWi layer
To heat the substrate so that the substrate temperature becomes 380 ° C.
Set the heater, and when the substrate is sufficiently heated,
Gradually open the valve shown_FourGas, C_TwoH_TwoMoth
S, H_TwoGas flows into the i-type layer deposition chamber 418.
I let you. At this time, SiH_Four50 sccm of gas, C_TwoH_TwoMoth
Is 35sccm, H_TwoThe gas will be 120 sccm
Adjust with each mass flow controller (not shown)
Was. The pressure in the i-type layer deposition chamber 418 is 6 mTo
rr. Next, set the RF power to 0.2 W
/ Cm ^TwoAnd applied to the bias bar. After that,
The power of the illustrated microwave power supply is 0.1 W / cm^TwoSet to
And microwave power is introduced into the i-type layer deposition chamber,
Generate glow discharge and open the shutter for RF
Start forming an MWi-type layer on the i-type layer,
When the i-type layer was formed, microwave glow discharge was stopped.
Thus, an MWi type layer was formed.

(C) Conditions for forming buffer layer a- has a wider band gap than the i-layer formed in (b).
The buffer layer made of Si is filled with 40 sc of SiH ₄ gas.
cm, C ₂ H ₂ gas is 60 sccm, and substrate temperature is 300 ° C.
Except for that, a layer thickness of 20 nm was deposited in the same manner as in (b).

Next, before forming the doping layer on the i-type semiconductor layer, NH ₃ is exposed to the plasma containing the element (γ) for expanding the band gap of the buffer layer B before exposing the surface of the buffer layer B. Gas and H ₂ gas in deposition chamber 4
A valve (not shown) was operated into 18 and gas was introduced through a gas introduction pipe 449. At this time, the NH ₃ gas was supplied at 10 sccm,
The H ₂ gas was adjusted to 500 sccm by a mass flow controller, and the pressure in the deposition chamber 418 was adjusted to 1.5 Torr. The temperature of the substrate 490 is maintained at 280 ° C., and the power of the RF power supply 424 is 0.1 W
/ Cm ² , RF power is introduced into the bias bar 428 to generate glow discharge, and the substrate is exposed to the above-mentioned plasma containing γ for 120 seconds, and only the vicinity of the surface of the deposited buffer layer made of a-Si has μc- The buffer layer 109 of the present invention was formed using SiCN: H.

(D) Conditions for forming p-type semiconductor layer A p-type semiconductor layer 105 of μc-SiCN was formed. The substrate temperature is 230 ° C., H ₂ gas is 50 sccm,
1 sccm of SiH ₄ / H ₂ gas and ₂ scc of C ₂ H ₂ gas
m, ₃ sccm of NH ₃ gas, 1 sc of BF ₃ / H ₂ gas
cm with a mass flow controller,
The opening of a conductance valve (not shown) was adjusted so that the pressure in the deposition chamber 419 was 2.0 Torr. The power of the RF power supply 423 was set to 0.15 W / cm ² , and RF power was introduced into the plasma forming cup 421.
A glow discharge is generated to start the formation of a p-type layer made of μc-SiCN.
The power was turned off, the glow discharge was stopped, and the formation was completed.

The other points were the same as in (Example 1). The photovoltaic element created in this example was called (SC Ex. 3).

(Comparative Example 3-1) In this example, before forming the doping layer on the i-type semiconductor layer, the surface of the buffer layer B was not exposed to the plasma containing γ (implementation). Different from Example 3).

The other points were the same as in (Example 3). The photovoltaic element produced in this example was called (SC ratio 3-1).

Hereinafter, (Example 3) and (Comparative Example 3-
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 5 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 3-1) (SC actual 3). (FF).

[0199]

[Table 5] From Table 5, it was found that the photovoltaic element of (SC Ex. 3) was superior in open-circuit voltage (V _OC ), fill factor (FF), and photoelectric conversion efficiency (η). .

(Embodiment 4) In this embodiment, instead of (Example 1) having the light incident side as a p-layer and the layer structure being substrate / n-layer / i-layer / p-layer, the light incident side is n-layer. The layer structure is defined as
The difference is that the layers are p-layer / i-layer / n-layer.

In the following, the conditions for forming the p-type layer made of a-Si, the conditions for exposing the surface of the doping layer to plasma, and the conditions for forming the i-type layer made of a-Si in the fabrication of the photovoltaic device of this example are described below. The conditions for forming the buffer layer according to the present invention in which only the upper portion is made of a-SiO and the n-type layer made of a-SiO will be described.

(A) Conditions for Forming a P-Type Layer The p-type layer was deposited by RF plasma CVD under conditions that would make a-Si. The substrate heating heater is set so that the substrate temperature becomes 350 ° C., and when the substrate temperature is stabilized, H
₂ gas, SiH ₄ gas, and BF ₃ / H ₂ gas were introduced into the deposition chamber 419. At this time, H ₂ gas is 30 scc
m, the SiH ₄ / H ₂ gas was adjusted to ₂ sccm and the BF ₃ / H ₂ gas was adjusted to 5 sccm by a mass flow controller, and the pressure in the deposition chamber 419 was 2.0 Torr.
It was adjusted to be. 0.05W /
cm ² , RF power was introduced into the plasma forming cup, glow discharge was generated, the formation of the p-type layer made of a-Si was started, and the RF power supply was started when the p-type layer having a thickness of 10 nm was formed. , The glow discharge was stopped, and the formation of the p-type layer made of a-Si was completed.

(B) Conditions for Forming MWi-Type Layer An MWi-type layer (i-type semiconductor layer formed by microwave CVD) was prepared under the same conditions as in (Example 1).

(C) Conditions for forming buffer layer In the same manner as in (b) except that the temperature of the substrate 490 was set to 300 ° C., a-Si: H having a wider band gap than the i-layer formed in (b). Buffer layer consisting of 25
nm.

Next, before forming an n-type doping layer
Next, the surface of the buffer layer B is
Exposure to plasma containing the element that widens the gap (γ)
O _Two/ He gas is introduced into the deposition chamber 418
Was. At this time,_Two/ He gas will be 300sccm
Adjust with the mass flow controller
Adjust the pressure inside -418 to 0.5 Torr.
Was. The power of the RF power supply is 0.06 W / cm^TwoSet to
RF power is introduced into the cup for plasma formation and glow discharge is performed.
And exposed to the plasma containing γ for 100 seconds.
Near the surface of the buffer layer made of a-Si: H
The buffer layer of the present invention was prepared
Was.

(D) Conditions for forming n-type layer In order to form an n-type layer, a heater for heating the substrate is set so that the substrate temperature becomes 230 ° C. When the substrate temperature becomes stable, H ₂ gas, SiH ₄ gas, O ₂ / He gas, PH ₃
/ H ₂ gas was introduced into the i-type layer deposition chamber 417. At this time, the H ₂ gas was 50 sccm, and the SiH ₄ gas was 2 sccm.
The mass flow controller was adjusted so that the sccm, the O ₂ / He gas became 4 sccm and the PH ₃ / H ₂ gas became 0.5 sccm, and the pressure in the deposition chamber 417 was 1 m.
It was adjusted to Torr. Next, the power of the RF power source is set to 0.005 W / cm ² , the RF power is introduced into the plasma forming cup, a glow discharge is generated, and the formation of the n-type layer is started. When the layer was formed, the RF power was turned off to stop glow discharge, and a-SiO
Was formed.

The other points were the same as in (Example 1). The photovoltaic element created in this example was called (SC Ex. 4).

(Comparative Example 4-1) In this example, before forming the doping layer on the i-type semiconductor layer, the surface of the buffer layer B was not exposed to the plasma containing γ (implementation). Different from Example 4).

The other points were the same as in (Example 4). The photovoltaic element produced in this example was called (SC ratio 4-1).

Hereinafter, (Example 4) and (Comparative Example 4-
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 6 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 4-1) (SC actual 4). (FF).

[0213]

[Table 6] From Table 6, it was found that the photovoltaic element of (SC Ex. 4) was superior in open-circuit voltage (V _OC ), fill factor (FF), and photoelectric conversion efficiency (η). .

(Embodiment 5) In this embodiment, instead of producing the single cell type photovoltaic element shown in FIG. 1 in (Example 1), a triple cell type (pin type) shown in FIG. (Stacked cell type) composed of a structure in which the semiconductor junction is laminated three times.

[0215] The photovoltaic element of this example used the deposition apparatus of FIG. The layer configuration of the photovoltaic element of this example is
Back electrode 202 / first pin junction 214 / second pi
n junction 215 / third pin junction 216 / transparent electrode 21
2 / current collecting electrode 213. Further, each pin junction had the following layer configuration from the substrate side.

The layer structure of each pin junction in this example is shown below. However, the element that enlarges the band gap of the buffer layer B is denoted by γ.

The first pin junction 214 is
N-type layer (n1 layer) made of μc-Si in order from side 2
203 / a-S buffer layer 251 / a-S
MWi type layer (i1 layer) 204 of iGe / top is a
The p-type layer (p1 layer) 205 made of a-SiC under the buffer layer 261 / μc-SiC of the present invention is formed under -SiC.
And

[0218] The second pin junction 215 is connected to the first pin junction 215.
In order from the junction 214 side, an n-type layer (n2 layer) 206 of μc-Si / a buffer layer 25 of a-Si
MWi type layer (i2 layer) 207 made of 2 / a-SiGe
/ The upper part is a-SiC. The lower part of the buffer layer 262 of the present invention made of a-Si / the p-type layer made of μc-Si (p2
Layer) 208.

The third pin junction 216 is connected to the second pin junction 216.
In order from the junction 215 side, an n-type layer (n3 layer) 209 of μc-Si / RFi layer 210 / a of a-Si
The upper part is μc-SiC, and the lower part is the buffer layer 263 of the present invention made of a-Si / p-type layer made of μc-SiC (p3
Layer) 211.

Hereinafter, a method of forming the first pin junction 214 will be described according to the procedure. The numbers in parentheses indicate the steps. (1) In order to form the n-type layer 203 made of μc-Si, the substrate temperature is set to 380 ° C. with a heater for heating the substrate, and SiH ₄ / H ₂ gas, PH ₃ / H ₂ gas, and H ₂ gas are supplied. It was introduced into the deposition chamber 417. At this time, SiH ₄ /
H ₂ gas is ₂ sccm, PH ₃ / H ₂ gas is 1 sccm,
The mass flow controller was used to adjust the H ₂ gas to 50 sccm, and the pressure in the deposition chamber 417 was adjusted to 1.1 Torr. RF power supply 422
Is set to 0.08 W / cm ² , RF power is introduced into the plasma forming cup, glow discharge is generated, the formation of an n-type layer made of μc-Si on the substrate is started, and the layer thickness is 10 nm. When the n-type layer was formed, the RF power was turned off to stop glow discharge, and an n-type layer made of μc-Si was formed.

(2) Buffer layer 25 made of a-Si
1. MWi type layer 204 made of a-SiGe, a-Si
Layer 261 made of RF plasma CVD
Method, microwave plasma CVD method, RF plasma CVD
Formed by the method.

(2-1) a-Si buffer layer
To create 251, set the substrate temperature to 350 ° C
Then, when the substrate is sufficiently heated, the Si_TwoH₆Gas, H
_TwoGas flowed into the deposition chamber 417. this
Time, Si_TwoH₆Gas is 4 sccm, H _TwoGas is 100sc
cm with each mass flow controller.
It was adjusted. The pressure in the deposition chamber 417 is 0.8 To
rr. Next, the RF power supply 422 is turned on.
0.007W / cm^TwoSet to the plasma forming cup
RF power is introduced into the
Opening a buffer layer to start creating a buffer layer on the n-type layer
When a buffer layer having a layer thickness of 10 nm was formed, R
Stop F glow discharge, turn off RF power output, buffer
-Finished creating layers.

(2-2) To form an MWi-type layer, the temperature of the substrate was set to 380 ° C., and when the substrate was sufficiently heated, SiH ₄ gas, GeH ₄ gas, and H ₂ gas were added to the i-type layer. Flowed into the deposition chamber 418. At this time, SiH
₄ gas 50 sccm, GeH ₄ gas 35 sccm, H
Each gas was adjusted by each mass flow controller so that _two gases became 120 sccm. i-type layer deposition chamber 41
The pressure in 8 was adjusted to 6 mTorr. Next, the RF power was set to 0.2 W / cm ² and applied to the bias bar. Thereafter, the power of the microwave power supply is reduced to 0.1 W / cm ²
, Microwave power is introduced into the i-type layer deposition chamber, a glow discharge is generated, and a shutter is opened to start forming an MWi-type layer on the RFi-type layer.
When the 1 μm i-type layer was formed, the microwave glow discharge was stopped, the output of the bias power supply was turned off, and the formation of the MWi-type layer was completed.

(2-3) The upper part of the present invention is characterized by a-
A buffer layer 261 made of a-Si was formed below the SiC. First, a buffer layer 261 made of a-Si was deposited. The temperature of the substrate was set at 300 ° C., and when the substrate was sufficiently heated, Si ₂ H ₆ gas and H ₂ gas were flowed into the deposition chamber 419. At this time, the respective mass flow controllers were adjusted so that the Si ₂ H ₆ gas was ₂ sccm and the H ₂ gas was 80 sccm. The pressure in the deposition chamber 419 was adjusted to be 0.7 Torr. Next, an RF power source was set to 0.007 W / cm ² , RF power was introduced into the plasma forming cup, glow discharge was generated, and a shutter layer was opened to start forming a buffer layer. When the buffer layer was deposited, the RF glow discharge was stopped, the output of the RF power supply was turned off, and the formation of the buffer layer was completed.

[0225] (2-4) before forming the p-type semiconductor layer 205, to expose the surface of the buffer layer B, and a plasma containing the element (gamma) to expand the band gap of the buffer layer B, CH ₄ gas, He gas was introduced into the deposition chamber 419. At this time, the mass flow controller was adjusted so that the CH ₄ gas was 1 sccm and the He gas was 30 sccm, and the pressure in the deposition chamber 419 was 1.0 T
Adjusted to orr. RF power is 0.0
At 6 W / cm ² , RF power was introduced into the plasma forming cup to generate glow discharge, and the substrate was exposed to the plasma containing γ for 150 seconds to form the buffer layer 261 of the present invention having a surface made of a-SiC. did.

(3) P-type semiconductor layer 2 made of μc-Si
05 was formed. Set the temperature of the substrate to 230 ° C,
When the temperature stabilizes, H_TwoGas, SiH_Four/ H_TwoMoth
Su, BF_Three/ H_TwoGas is introduced into the deposition chamber 419
Was. At this time, H_Two50 sccm gas, SiH_Four/ H_TwoMoth
0.5 sccm, BF_Three/ H_Two0.5 sccm gas
Adjust with the mass flow controller so that
The pressure in the deposition chamber is set to 2.0 Torr
It was adjusted. The power of the RF power supply 423 is set to 0.15 W / cm ^Two
RF power is introduced to the cup for plasma formation
To generate a glow discharge, thereby forming a p-type layer made of μc-Si.
Is formed, and when a layer thickness of 7 nm is formed, RF power is applied.
The source was turned off, the glow discharge was stopped, and the formation was completed. Like this
Thus, the formation of the first pin junction was completed.

In the following, a method of forming the second pin junction 215 will be described. (4) In the step of forming the second pin junction 215, a-S
Only the conditions for forming the MWi type layer made of iGe are different from those of the step of forming the first pin junction 214. What changed in the conditions for forming the MWi type layer made of a-SiGe
50 sccm of H ₄ gas, 30 sccm of GeH ₄ gas,
The point is that the H ₂ gas is set to 120 sccm. Through the above steps, formation of the second pin junction 215 has been completed.

In the following, a method for forming the third pin junction 216 will be described according to the procedure. The numbers in parentheses indicate the steps. (5) In order to form the n-type layer 209 made of μc-Si, a substrate heating heater was set at a substrate temperature of 320 ° C. Otherwise, the n-type layer of the present invention was formed in the same manner as the n-type layer in the second pin junction.

(6) The i-type layer 210 is formed by RF plasma CVD.
Created by law. Set the temperature of the substrate to 200 ° C,
When the substrate is sufficiently heated, Si ₂ H ₆ gas and H ₂ gas are supplied through the gas introduction pipe 449 to the i-type layer deposition chamber 4.
18. At this time, 8 scc of Si ₂ H ₆ gas
m, H ₂ gas was adjusted with mass flow controllers each so that 300 sccm. The pressure in the i-type layer deposition chamber 418 was adjusted to be 0.6 Torr. Next, set the RF power supply to 0.01 W / cm ² ,
By applying a glow discharge to a bias rod to generate a glow discharge and opening a shutter, the formation of an i-type layer is started, and a layer thickness of 95 n
When the m-type i-layer is formed, the RF glow discharge is stopped,
The output of the RF power supply was turned off, and the formation of the i-type layer 210 was completed.

(7) A 10-nm thick layer of a-Si
Under the conditions for forming the buffer layer 263, the substrate temperature is set to 200.
Deposit in the same manner as for the buffer layer 261 except for setting the temperature to
did. (8) Before forming the p-type semiconductor layer 211, a buffer
Enlarge the band gap of buffer layer B on the surface of layer B
Exposed to plasma containing the element (γ) _FourMoth
S, H_TwoGas was introduced into the deposition chamber 419. This
Time, CH_Four1 sccm gas, H_Two30 sccm of gas
Adjust with mass flow controller so that
The pressure in the chamber 419 is set to 1.0 Torr
Was adjusted. The power of the RF power supply is 0.06 W / cm^TwoSet in
RF power into the plasma forming cup
-Discharge is generated and the plasma containing γ is generated for 100 seconds.
Exposure, buffer of the present invention whose surface is composed of μc-SiC
Layer 263 was created.

(9) In order to form the p-type semiconductor layer 211 made of μc-SiC, the temperature of the substrate was set at 170 ° C. H ₂ gas is 50 sccm, SiH ₄ / H ₂ gas is 0.
The flow rate was adjusted so that 5 sccm, C ₂ H ₂ gas was 1 sccm, and BF ₃ / H ₂ gas was 0.5 sccm. Otherwise, a p-type semiconductor layer 211 made of μc-SiC having a thickness of 4 nm was formed in the same manner as the p-type layers in the second and third pin junctions. Through the above steps, the formation of the third pin junction 216 has been completed.

(8) On the p-type layer 211, the transparent conductive layer 21
As No. 2, ITO having a layer thickness of 70 mm was vacuum deposited by a vacuum deposition method. Next, a mask having a comb-shaped hole is placed on the transparent conductive layer 212, and Cr (40 nm) / Ag (1000 n
m) / Cr (40 nm) comb-shaped current collecting electrode 213
Was vacuum deposited by a vacuum deposition method. The photovoltaic element produced in this example was called (SC Ex. 5).

(Comparative Example 5-1) In this example, the point that the surface of the buffer layer B was not exposed to the plasma containing γ before forming the p-type semiconductor layer on the i-type semiconductor layer. (Example 5) is different.

The other points were the same as in (Example 5). The photovoltaic element produced in this example was called (SC ratio 5-1).

In the following, (Example 5) and (Comparative Example 5-
An evaluation test performed on each of the six photovoltaic elements obtained in 1) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 7 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 5-1) (SC actual 5). (FF).

[0238]

[Table 7] From Table 7, it was found that the photovoltaic element of (SC Ex. 5) was superior in open-circuit voltage (V _OC ), fill factor (FF), and photoelectric conversion efficiency (η). .

(Comparative Example 5-2) In this example, the following three points are different from (Example 5). (A) When forming the buffer layers 261, 262 and 263, the SiH ₄ / H ₂ gas is ₂ sccm and the C ₂ H ₂ gas is 2 sccm.
The mass flow controller was adjusted so that the sccm and H ₂ gas became 50 sccm, and the pressure in the deposition chamber was adjusted so as to be 1.1 Torr.

(B) Buffer layers 261, 262, 26
3 when the power of the RF power source is 0.03 W / cm
Set to ² . (C) The step of exposing the surface of the buffer layer B to the plasma containing γ before forming the p-type semiconductor layer on the i-type semiconductor layer was omitted. Other points were the same as in (Example 5).

In the following, (Example 5) and (Comparative Example 5-
An evaluation test performed on each of the six photovoltaic elements obtained in 2) will be described.

As an evaluation test, each photovoltaic element was
VI characteristics were observed by installing the device under 1.5 (100 mW / cm ² ) light irradiation. From the results, average values of photoelectric conversion efficiency (η), which is photoelectromotive force / incident optical power, open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor (FF) were calculated.

Table 8 shows the photoelectric conversion efficiency (η), open-circuit voltage (V _OC ), short-circuit current (J _SC ), and fill factor normalized by the measured value of (SC ratio 5-2) (SC actual 5). (FF).

[0244]

[Table 8] From Table 8, it was found that the photovoltaic element of (SC Ex. 5) was superior in open-circuit voltage (V _OC ), fill factor (FF), and photoelectric conversion efficiency (η). .

Also, in order to observe the variation in characteristics in the substrate, when depositing ITO, a mask having a hole of 0.25 cm ² was used, so that 25 light beams divided in one substrate were used. An electromotive element was created. Table 9 shows the results of examining the in-substrate variations in the open circuit voltage (V _OC ) and fill factor (FF) for such a sample. However, the maximum value on the same substrate was set to 1.

[0246]

[Table 9] From Table 9, it was found that the photovoltaic element of (SC Ex. 5) had improved uniformity of the photoelectric conversion characteristics because the variation in the substrate was smaller than that of the photovoltaic element.

[0247]

As described above, according to the first aspect of the present invention, there is provided a semiconductor device comprising a p-type semiconductor layer and an n-type semiconductor layer.
P with two doping layers stacked via an i- type semiconductor layer
has in semiconductor junction of and method of manufacturing at least the i-type semiconductor layer photovoltaic device crystalline form of the doping layer D is amorphous located above the said i-type semiconductor layer When a buffer layer B is provided between the doping layer D and the element that expands the band gap of the buffer layer B is γ, the buffer layer B is formed following the i-type semiconductor layer, and then the doping is performed. By exposing the surface of the buffer layer B to the plasma containing γ before forming the layer D, the optical band gap of the doping layer D could be increased. In addition, the buffer layer could be formed uniformly over a large area.

[0248] According to the invention of claim 2, has a semiconductor junction of the pin-type p-type semiconductor layer and the n-type semiconductor layer two doped layers made of is laminated via the i-type semiconductor layer, and In a photovoltaic device in which the crystal form of the doping layer D located at least on the i-type semiconductor layer is amorphous, a buffer layer B is provided between the i-type semiconductor layer and the doping layer D; When the element that enlarges the band gap of the buffer layer B is γ, the buffer layer B is formed by the method for manufacturing a photovoltaic device according to claim 1, whereby the i-type semiconductor layer and the Since the difference in the composition and lattice constant of the doping layer D was reduced and the interface state between the i-type semiconductor layer and the doping layer D was reduced, the built-in potential of the photovoltaic element increased. Photovoltaic open circuit voltage of the power element (V _OC) and fill factor (F.F.) is increased, the photoelectric conversion efficiency is improved.

According to the third aspect of the present invention, a pin-type semiconductor junction in which two doping layers consisting of a p-type semiconductor layer and an n-type semiconductor layer are stacked via an i- type semiconductor layer is formed.
In a stack cell type photovoltaic device having a structure laminated more than once, a buffer layer B is provided between the i-type semiconductor layer and the doping layer D, and an element for expanding the band gap of the buffer layer B is γ. When at least one of the buffer layers B is formed by the method for manufacturing a photovoltaic device according to claim 1, the composition and the lattice of the i-type semiconductor layer and the doping layer D are formed. Since the difference between the constants was reduced and the interface state between the i-type semiconductor layer and the doping layer D was reduced, the built-in potential of the pin junction at that portion increased,
The open-circuit voltage (V _OC ) and fill factor (FF) of the entire stack type photovoltaic element were increased, and the photoelectric conversion efficiency was improved.

According to the invention of claim 4, the element γ for expanding the band gap contained in the buffer layer B is used.
The composition ratio, over its thickness direction, since the changes, increases in potential further photovoltaic element, open circuit voltage (V _OC) and fill factor of the photovoltaic element (F.F.) Increased, and the photoelectric conversion efficiency was further improved.

According to the fifth aspect of the present invention, since the buffer layer B is partially microcrystallized or polycrystallized in the thickness direction, the built-in potential of the photovoltaic element further increases. The open-circuit voltage (V _OC ) and fill factor (FF) of the photovoltaic element were increased, and the photoelectric conversion efficiency was further improved.

Furthermore, as an effect common to the claims of the present invention, the buffer layer can be formed uniformly over a large area, and the photovoltaic element can be formed over a large area. Since the buffer layer has a small thickness, its thickness distribution and characteristic distribution over a large area strongly affect the characteristic distribution over a large area of the photovoltaic element.
Since the thickness distribution and the characteristic distribution of the buffer layer can be made uniform, the characteristic distribution of the photovoltaic element is also made uniform.

Further, according to the present invention, a condition in which the energy of ions is large is not required at the time of depositing the buffer layer, and the stress inside the buffer layer is alleviated by the plasma treatment. The adhesion was improved, and the production yield of the photovoltaic element was improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a layer configuration of a single-cell type photovoltaic element according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a layer configuration of a stack cell type photovoltaic element according to the present invention.

FIG. 3 is a schematic view of an example of a photovoltaic element according to the present invention as viewed from above.

FIG. 4 is a schematic explanatory view of a multi-chamber separation type deposition apparatus used for forming a photovoltaic element according to the present invention.

[Explanation of symbols]

101, 201 substrate, 102, 202 back electrode, 103 n layer, 104 i layer, 105 p layer, 106, 212 transparent electrode, 107, 213 current collecting electrode, 108, 109 buffer layer, 203 n1 layer, 204 i1 layer, 205 p1 layer, 206 n2 layer, 207 i2 layer, 208 p2 layer, 209 n3 layer, 210 i3 layer, 211 p3 layer, 214 first pin junction, 215 second pin junction, 216 third pin junction, 251 , 252, 261, 262, 263 Buffer layer 400 Multi-chamber separation type deposition apparatus, 401 Load lock chamber, 402 Transfer chamber for n-type layer (or p-type layer), 403 MW-i layer (or RF-i layer) 404) transfer chamber for p-type layer (or n-type layer), 405 unload chamber, 406, 407, 408, 40 Gate valve, 410, 411, 412 Heater for heating substrate, 413 Rail for transporting substrate, 417 Deposition chamber for n-type layer (or p-type layer), 418 Deposition chamber for MW-i layer (or RF-i layer) 419 Deposition chamber for p-type layer (or n-type layer), 420, 421 RF introduction cup, 422, 423 RF power supply, 424 bias application power supply, 425 MW introduction window, 426 MW introduction waveguide, 427 MW-i layer deposition shutter, 428 bias electrode, 429 gas supply pipe of n-type layer (or p-type layer) deposition gas supply facility, 449 MW-i layer (or RF-i layer) deposition gas supply facility 469, a gas supply pipe of a gas supply facility for p-type layer (or n-type layer) deposition.

Claims (5)

(57) [Claims] 1. A has a semiconductor junction of the p-type semiconductor layer and a pin-type in which two doped layers made of n-type semiconductor layer are stacked via an i-type semiconductor layer, and at least the i
The method of manufacturing a photovoltaic device crystalline form is a non-single-crystal of the doping layer D overlying the type semiconductor layer, a buffer <br/> over layer between the doped layer D and the i-type semiconductor layer B, when the element that expands the band gap of the buffer layer B is γ, after forming the buffer layer B following the i-type semiconductor layer, and before forming the doping layer D, the buffer A method for manufacturing a photovoltaic device, comprising exposing the surface of the layer B to the plasma containing γ. 2. A has a semiconductor junction of the p-type semiconductor layer and a pin-type in which two doped layers made of n-type semiconductor layer are stacked via an i-type semiconductor layer, and at least the i
In the photovoltaic device crystalline form of the doping layer D is a non-single crystal overlying the type semiconductor layer, a buffer <br/> over layer B is provided between the doped layer D and the i-type semiconductor layer A photovoltaic device, wherein the buffer layer B is formed by the method for manufacturing a photovoltaic device according to claim 1. 3. A stacked cell type having a structure in which a pin-type semiconductor junction in which two doping layers composed of a p-type semiconductor layer and an n-type semiconductor layer are laminated via an i- type semiconductor layer is laminated twice or more. In the photovoltaic device, a buffer layer B is provided between the i-type semiconductor layer and the doping layer D, and at least one of the buffer layers B is a photovoltaic device according to claim 1. A photovoltaic element formed by a method for manufacturing a power element. 4. The γ contained in the buffer layer B
4. The photovoltaic device according to claim 2, wherein the composition ratio of the photovoltaic device changes over the thickness direction. 5. The photovoltaic device according to claim 2, wherein the buffer layer B is partially crystallized or polycrystallized in the thickness direction. .