JP2004095669A - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element (optical battery) having electrode structure capable of forming a thin film optical battery without using a transparent electrode including problems in the improvement of performance, and capable of obtaining high performance at low costs. <P>SOLUTION: The photoelectric conversion element is provided with a light transmitting substrate 20, a semiconductor layer 30 formed by a plurality of layers consisting of p-layers or n-layers on the rear side of the substrate 20 and capable of generating and collecting carriers, a 1st rear electrode 62 formed in an aperture part 40 formed on the semiconductor layer 30 connected to a layer 32 which is the most light receiving face side of the layer 30 and constituted so as not to be connected to layers 34, 36 other than the layer 32 of the most light receiving face side of the layer 30 by an insulating film 50 formed in the aperture part 40, and a 2nd rear electrode 66 connected to the most rear side layer 36 of the semiconductor layer 30. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photoelectric conversion element that converts light energy into electric energy, and more particularly, to a photoelectric conversion element (photocell, solar cell) suitable for thermophotovoltaic power generation.
[0002]
[Prior art]
BACKGROUND ART As a technique for directly obtaining electric energy from fossil fuels and combustible gases, power generation by thermophotovoltaic energy conversion, that is, thermophotovoltaic power generation (TPV) has attracted attention. The mechanism of TPV is to apply the heat of combustion from a heat source to a luminous body (radiator, emitter) to generate radiant light from the luminous body and irradiate the light to the photoelectric conversion element to obtain electric energy. It is. Since the TPV system has no moving parts, a low-noise and low-vibration system can be realized. As a next-generation energy source, TPV is excellent in cleanliness and quietness.
[0003]
In TPV, infrared light obtained from a luminous body at a temperature of 1000 to 1700 ° C is used. In order to convert light having a wavelength of 1.4 to 1.7 μm emitted from the luminous body into electricity, it is necessary to use a photoelectric conversion element made of a material having a small band gap (Eg). Since Si (silicon), which is a general material, can convert only light having a wavelength of 1.1 μm or less into electricity, it cannot be used.
[0004]
As a photoelectric conversion element for a TPV system, a material having a band gap (Eg) of 0.5 to 0.7 eV is suitable. Representative materials include GaSb (gallium antimony, Eg = 0.72 eV), InGaAs (indium gallium arsenide, Eg = 0.60-1.0 eV), Ge (germanium, Eg = 0.66 eV), and the like.
[0005]
As a method of increasing the energy efficiency of the TPV, reducing the amount of expensive photoelectric conversion elements used, and reducing the cost, there is a method of increasing the intensity of light generated from the light emitter. When the light intensity is increased by 100 times, the usage of the photoelectric conversion element is reduced to 1/100, the cost can be greatly reduced, and the energy conversion efficiency can be improved.
[0006]
In that case, the generated current increases. Therefore, in the conventional photoelectric conversion element, it is necessary to greatly increase the area of the electrode on the light receiving surface side in order to reduce the resistance loss. However, when the area of the electrode on the light receiving surface side increases, the amount of light incident on the photoelectric conversion element decreases, which causes a problem that the increase in light intensity cannot be utilized.
[0007]
On the other hand, there is a structure of a back electrode type having no electrode on the light receiving surface side, which is used for a concentrating power generation system. However, this back electrode type can be realized only by an indirect transition type material having a large carrier diffusion length, and is actually realized only by Si. Ge (germanium) is an indirect transition type material having a small band gap. At present, a photoelectric conversion element using Ge as a material and employing a back electrode type as an electrode structure has not been put to practical use.
[0008]
Therefore, the applicant of the present application, for example, in the specification and drawings attached to the application of Japanese Patent Application No. 2001-173017, in order to establish a back electrode type photoelectric conversion element using Ge suitable for the TPV system, A device structure capable of greatly reducing the recombination loss of carriers at the surface has already been proposed.
[0009]
[Problems to be solved by the invention]
As mentioned above, Ge back electrode type photovoltaic cells are very suitable for TPV systems. Also, its manufacturing cost is lower than that of a conventional III-V compound photocell such as GaSb. However, in order to further reduce the cost, it is required to form a photovoltaic cell by forming a semiconductor layer in a thin film on an inexpensive substrate such as glass.
[0010]
However, as shown in FIG. 1, in the current thin-film battery, a semiconductor layer (p-layer, i-layer, and n-layer) 30 is formed on the back surface side of a light-transmitting substrate (glass) 20, and light reception of the semiconductor layer is performed. It has a structure in which a transparent electrode 60 is provided on the front side and a metal electrode 61 is provided on the back side. This transparent electrode 60 has a problem that the resistance increases when light transmittance is increased. In particular, in a TPV system, the light intensity is higher than that of sunlight, and the current density generated by the photovoltaic cell is large. Therefore, the problem that the resistance of the electrode is large is a great obstacle to improving the performance of the photovoltaic cell. .
[0011]
Further, in the current thin-film battery, as shown in FIG. 1, since the transparent electrode 60 is provided on the entire light-receiving surface side and is connected to the semiconductor layer 30, it is difficult to reduce defects at the semiconductor interface. It is an obstacle to performance improvement.
[0012]
The present invention has been made in view of the above-described problems, and has as its object to provide a low-cost, high-performance, low-cost, high-performance thin-film photovoltaic cell without using a transparent electrode, which is a problem in terms of performance improvement. Another object of the present invention is to provide a simple photoelectric conversion element (photocell). Another object of the present invention is to provide a structure on the light receiving surface side of the photoelectric conversion element (photovoltaic cell) that can reduce defects at the semiconductor interface.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, according to a first aspect of the present invention, a light-transmitting substrate and a plurality of p-layers or n-layers on a back surface side of the light-transmitting substrate are formed to generate carriers. And a semiconductor layer that performs collection, and is provided in an opening formed in the semiconductor layer and connected to a layer closest to the light receiving surface of the semiconductor layer, and an insulating film provided in the opening forms an insulating film of the semiconductor layer. Provided is a photoelectric conversion element comprising: a first back electrode that is not connected to a layer other than the layer on the light receiving surface side; and a second back electrode that is connected to a layer on the back surface side of the semiconductor layer. Is done. In this photoelectric conversion element, an electrode structure constituting a thin-film photovoltaic cell is realized without using a transparent electrode having a large resistance loss.
[0014]
According to the second aspect of the present invention, the opening is formed wider toward the rear side. With this configuration, light reaching the side surface of the opening is reflected inside the element and absorbed by the semiconductor layer, and loss of incident light is minimized.
[0015]
According to a third aspect of the present invention, a defect reduction film is provided between the light transmitting substrate and the semiconductor layer. According to such a configuration, it is possible to prevent impurity elements (which degrade the performance of the photoelectric conversion element) included in the substrate from diffusing into the semiconductor layer.
[0016]
Further, according to a fourth aspect of the present invention, the defect reduction film contains hydrogen or a halogen element. Semiconductor layer with other substances (SiNx, SiO ₂ or the like) in the interface between There are many defects, where in order to improve the performance of the photoelectric conversion element is essential to reduce the defect, such a construction According to the method, defects are reduced by bonding of dangling bonds on the light receiving surface side of the semiconductor layer to hydrogen or a halogen element.
[0017]
Further, according to the fifth aspect of the present invention, the opening is formed in a line shape or a dot shape. By forming the shape of the opening in a line shape or a dot shape, it is possible to reduce the electrode resistance while suppressing a decrease in incident light.
[0018]
Further, according to the sixth aspect of the present invention, the collective electrode is further provided via the second insulating film. According to such a configuration, the collective electrode can be provided without increasing the area of the element, so that the efficiency can be improved.
[0019]
According to a seventh aspect of the present invention, a semiconductor substrate containing silicon as a main component is used instead of the light transmitting substrate. According to such a configuration, it becomes possible to form a semiconductor layer with less defects as compared with the case where a light transmitting substrate is used.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0021]
FIG. 2 is a sectional view showing a first embodiment of the photoelectric conversion element according to the present invention. First, the basic configuration of the photoelectric conversion element shown in FIG. 2 will be described from the light receiving surface side. The multilayer light control thin film 10 includes an antireflection film for reducing light reflection loss and light effective for power generation of the cell. This is an optical filter for transmitting and reflecting unnecessary light. The light transmitting substrate 20 is a substrate that transmits light useful for a photovoltaic cell. As the light transmissive substrate 20, quartz, glass, plastic, or the like is used.
[0022]
The semiconductor layer 30 absorbs light and generates charges (carriers). Due to the pn junction composed of the n ⁺ layer 32 and the p layer 34, electrons (minus carriers) move to the n ⁺ layer 32 and holes (plus carriers) move to the p ⁺ layer 36. In addition, the carrier concentration of the n ⁺ layer 32 and the p ⁺ layer 36 serving as semiconductor layers connected to the electrodes is increased, and the contact resistance with the electrodes is reduced.
[0023]
opening to connect to the n ⁺ layer 32 (- electrode formation portion) 40, an upper connecting the n ⁺ layer 32 is narrow, is formed to be wider toward the bottom. The top is provided on the light receiving surface side of the interface between the n ⁺ layer 32 and the p layer 34. Although the opening is formed wider toward the rear surface side, this shape is preferable and is not a requirement for forming a photovoltaic cell. It may be.
[0024]
The insulating film 50 is provided to insulate and separate the minus fine electrode 62 connected to the n ⁺ layer 32 from the p layer 34 and the p ⁺ layer 36. The minus fine electrode (first back electrode) 62 is formed so as to fill the opening 40. Thus, the opening 40 is provided on the back surface side to provide an electrode connected to the n ⁺ layer 32 on the light receiving surface side (the layer closest to the light receiving surface of the semiconductor layer 30). The plus fine electrode (second back surface electrode) 66 is an electrode connected to the p ⁺ layer 36 (the rearmost layer of the semiconductor layer 30).
[0025]
In the configuration of FIG. 2, the wide gap semiconductor thin film 32 provided as the layer closest to the light receiving surface of the semiconductor layer is of the n-type, but a similar configuration can be manufactured by replacing the p-layer and the n-layer. It is.
[0026]
The operation of the photoelectric conversion element having the basic configuration shown in FIG. 2 will be described. A negative electrode 62 connected to the semiconductor layer (n ⁺ layer) 32 on the light receiving surface side can be formed on the back surface side. In addition, by making the opening 40 wider toward the lower part, incident light that reaches the side surface of the opening can be reflected inside the photovoltaic cell and absorbed by the semiconductor thin film 30. Therefore, the loss of the incident light amount due to the shadow of the electrode occurs only in the portion where the minus electrode 62 and the n ⁺ layer 32 are in contact with each other, and can be minimized. Also, by increasing the opening 40 toward the lower part, the volume of the electrode can be increased, and the resistance loss can be reduced. Further, by forming the opening 40 so as to be buried in the n ⁺ layer 32 side and forming the insulating film 50, the n ⁺ layer 32 is maintained while the insulation between the minus electrode 62 and the p layer 34 and the p ⁺ layer 36 is maintained. The contact area between the electrode and the electrode 62 can be increased, and the resistance loss can be reduced.
[0027]
Thus, according to the photoelectric conversion element shown in FIG. 2, a thin-film photovoltaic cell (thin-film solar cell) formed on the back side of the light-transmitting (glass) substrate 20 can be formed without using a transparent electrode having a large resistance loss. Therefore, the resistance of the electrode can be reduced. Therefore, a high-performance photovoltaic cell suitable for high light density can be provided at low cost. As a result, when used in a TPV system, it is possible to reduce the cost of the system while increasing the amount of power generated by the TPV system.
[0028]
Here, an example of a specific structure (material configuration) based on FIG. 2 will be described. The multilayer light control thin film 10 is a multilayer film composed of MgF ₂ , ZnS, SiO ₂ , TiO ₂ , and the like. The multilayer film transmits light in a wavelength region that can be converted into a current by the photoelectric conversion element out of the light generated by the light-emitting body (emitter) of the TPV, and allows the semiconductor layer to absorb the unnecessary light. The reflection prevents the element temperature from rising.
[0029]
The light transmissive substrate 20 is made of quartz, glass, plastic, or the like, and has a thickness of about 0.2 to 5 mm and a size of about 1 cm × 1 cm to 100 cm × 100 cm.
[0030]
The material of the semiconductor layer 30 is carbon (C), AlGaAs, CdSe, CdTe, amorphous Si (a-Si), SiGaAs, InP, AlGaAs, GaInP, InGaAs, Ge, PbS, InAs, InSb, or the like. The band gap of the semiconductor layer 30 is about 0.2 to 2.0 eV. The n ⁺ layer 32 has a thickness of 0.02 to 1 μm and a carrier concentration of 1 × 10 ¹⁷ to 1 × 10 ²⁰ cm ⁻³ . The p layer 34 has a thickness of 1 to 30 μm and a carrier concentration of 1 × 10 ¹⁴ to 1 × 10 ¹⁸ cm ⁻³ . The p ⁺ layer 36 has a thickness of 0.02 to 1 μm and a carrier concentration of 1 × 10 ¹⁷ to 1 × 10 ²⁰ cm ⁻³ .
[0031]
The opening 40 connected to the n ⁺ layer 32 has an upper width of about 1 to 50 μm and a lower width of about 5 to 200 μm. The ratio of the area where the n ⁺ layer 32 contacts the negative electrode 62 to the battery area is 3%. The insulating film 50 is made of a material such as SiO ₂ or SiNx, and has a thickness of 200 to 500 nm. The material of the fine electrodes 62 and 66 is Al, Ag, Pd, Ti, Au, Cu, Ni, Cr, or the like.
[0032]
Note that the combination of the p-layer and the n-layer is not limited to the above-described specific example, and a reverse combination can be used.
[0033]
FIG. 3 is a sectional view showing a second embodiment of the photoelectric conversion element according to the present invention. In FIG. 3, the same elements as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. Explaining the difference between the structure of FIG. 2 and the structure of FIG. 3, a defect reduction film 70 is provided between the light-transmitting substrate 20 and the semiconductor layer 30. The defect reduction film 70 is an insulating thin film mainly composed of SiNx, SiO ₂ or the like, and transmits 90% or more of light having a wavelength of 300 to 2000 nm.
[0034]
The function of the photoelectric conversion element having the basic configuration shown in FIG. 3 will be described. The defect reduction film 70 is used for preventing the element included in the light transmitting substrate 20 from deteriorating the performance of the photovoltaic cell from diffusing into the semiconductor layer 30. prevent. That is, an inexpensive substrate 20 such as glass or plastic contains an element that forms an electrical defect in the semiconductor layer 30, such as an alkali metal element. In order to form the semiconductor layer 30, heat treatment at 200 to 800 ° C. is performed. During this heat treatment, elements that form defects diffuse into the semiconductor layer 30. An insulating thin film such as SiNx or SiO ₂ has an effect of preventing diffusion of these elements. In the conventional thin-film photovoltaic cell (FIG. 1), the semiconductor layer (n ⁺ layer) on the light receiving surface side needs to be connected to the transparent electrode. Therefore, a defect reduction film cannot be applied.
[0035]
Thus, according to the photoelectric conversion element shown in FIG. 3, by using the defect reduction film 70, the defects of the semiconductor layer 30 can be reduced and the photoelectric conversion efficiency can be improved.
[0036]
Here, an example of a specific structure (material configuration) based on FIG. 3 will be described. The defect reduction film 70 is made of SiNx and has a thickness of 3 nm to 3 μm. Other components are the same as in the example of FIG.
[0037]
FIG. 4 is a sectional view showing a third embodiment of the photoelectric conversion element according to the present invention. In FIG. 4, the same elements as those in FIG. 2 or 3 are denoted by the same reference numerals, and description thereof will be omitted. The difference of the structure of FIG. 4 from the structure of FIG. 2 or 3 will be described. The defect reduction film 170 contains 0.1 ppm to 20% of hydrogen or a halogen element. Therefore, as shown in FIG. 5, at the interface 30a on the light-receiving surface side of the semiconductor layer 30, a main element (germanium) forming the semiconductor layer can be combined with hydrogen or a halogen element.
[0038]
Therefore, when the dangling bond is bonded to hydrogen or a halogen element, electric defects at the light receiving surface side interface 30a of the semiconductor layer 30 are reduced. That is, heat treatment at 200 to 800 ° C. is performed during the formation of the semiconductor layer. During this heat treatment, hydrogen or a halogen element contained in the defect reduction film 170 diffuses and bonds to dangling bonds at the semiconductor layer interface 30 a. In the conventional thin-film type photovoltaic cell (FIG. 1), the semiconductor layer (n ⁺ layer) on the light receiving surface side needs to be connected to the transparent electrode. Therefore, it is necessary to use a defect reduction film to reduce interface defects. Can not. Thus, according to the photoelectric conversion element shown in FIG. 4, defects at the interface of the semiconductor layer are reduced, so that the photoelectric conversion efficiency can be improved.
[0039]
Here, as an example of the configuration of the defect reduction film 170 in FIG. 4, the material is SiO ₂ , the film thickness is 3 nm to 3 μm, the additive element is H ₂ , and the concentration is 2%.
[0040]
By the way, in the cross-sectional views of FIG. 2, FIG. 3 or FIG. 4, it has been described that the opening 40 for forming the negative electrode 62 connected to the n ⁺ layer 32 is formed wider toward the back surface side. However, the specific shape can be a line shape as shown in the perspective view of FIG. 6, or a dot shape as shown in the perspective view of FIG.
[0041]
In any case, the area where the n ⁺ layer at the top of the opening and the negative electrode are connected is set to 10% or less of the photovoltaic cell area. In order to sufficiently reduce the resistance loss and minimize the shadow due to the electrodes, it is optimal to set the line shape to 2 to 5% and the dot shape to 0.3 to 2%.
[0042]
Either a line shape or a dot shape can be selected in consideration of ease of fabrication, cost, resistance loss, and the like. An advantage of the line shape is that processing of the opening and formation of the electrode are easy, and the cost can be reduced. On the other hand, an advantage of the dot shape is that the incident light loss due to the shadow of the electrode can be reduced.
[0043]
Thus, when the opening is formed in a line shape or a dot shape as shown in FIG. 6 or FIG. 7, in the thin-film photovoltaic cell, the decrease in the amount of incident light due to the shadow of the electrode is minimized, and the electrode resistance is reduced. Can be reduced. Therefore, a high-performance photovoltaic cell suitable for high light density can be provided.
[0044]
Here, an example of a specific structure based on FIGS. 6 and 7 will be described. In the case of the line shape of FIG. 6, the upper size is 20 μm, the lower size is 50 μm, the opening pitch is 0.7 mm, and the n ⁺ layer The ratio of the area where the electrode contacts the negative electrode to the battery area is 3%. On the other hand, in the case of the dot shape of FIG. 7, the upper size is 40 μm, the lower size is 80 μm, the opening pitch is 0.5 mm, and the ratio of the area of contact between the n ⁺ layer and the negative electrode to the battery area is 0.64. %.
[0045]
By the way, in the structure shown in FIG. 2, FIG. 3, or FIG. 4, only the minus fine electrodes 62 and the plus fine electrodes 66 are formed alternately, and current cannot be taken out as it is. In view of the above, the present invention provides a structure for collecting a plurality of fine electrodes having a two-layered electrode structure and providing a collective electrode for extracting a current to the outside.
[0046]
FIG. 8 is a perspective view showing such a two-layer electrode structure, and FIG. 9 is a partially exploded perspective view showing the structure for convenience of explanation. As shown in these figures, minus minute electrodes 62 and plus minute electrodes 66 are provided alternately. The minus electrode 62 is connected to the n ⁺ layer 32 through the opening, and the plus electrode 66 is connected to the p ⁺ layer 36. Then, a second insulating film 80 is provided on the back side of the fine electrodes 62 and 66. The insulating film 80 is provided with an opening for connecting to the minus fine electrode 62 and the plus fine electrode 66 as shown in FIG. Then, a minus collective electrode 92 and a plus collective electrode 96 are provided on the back surface side of the second insulating film 80.
[0047]
The operation of the two-layer electrode structure shown in FIGS. 8 and 9 will be described. By providing the minus collective electrode 92 and the plus collective electrode 96 via the second insulating film 80, without increasing the area of the photovoltaic cell, An electrode for extracting electric power to the outside can be formed. Further, by providing both the minus and plus collective electrodes on the back surface side, it is possible to facilitate the attachment to the device.
[0048]
Thus, according to the two-layer electrode structure shown in FIGS. 8 and 9, the collective electrode can be provided without increasing the area of the photovoltaic cell, so that the performance (output power per area) can be maintained. Further, since the device can be easily attached to the device, the cost of the device can be reduced and the reliability can be improved.
[0049]
Here, an example of a specific structure based on FIGS. 8 and 9 will be described. The fine electrodes 62 and 66 are made of Al, Ti, Au, or the like, and the plus fine electrode 66 has a thickness of 0.5 to 5 μm. The second insulating film 80 is made of photosensitive polyimide and has a thickness of 1 to 10 μm. The collective electrodes 92 and 96 are made of Pd, Ag, Cu, solder, or the like, and have a thickness of 0.5 to 20 μm.
[0050]
FIG. 10 is a sectional view showing a fourth embodiment of the photoelectric conversion element according to the present invention. In this embodiment, a semiconductor substrate mainly containing silicon is used instead of the light-transmitting substrate. Explaining the basic configuration of the photoelectric conversion element shown in FIG. 10 from the light receiving surface side, the antireflection film 110 is an optical thin film having one to three layers for reducing light reflection loss. A crystalline Si substrate 120 such as a polycrystalline or single crystal is a semiconductor substrate that transmits infrared light. The crystalline Si back side n ⁺ layer 122 is a semiconductor layer formed on the back side of the Si substrate to form a hetero pn junction with the lower narrow gap semiconductor thin film 130.
[0051]
The n ⁺ layer 122 and the narrow gap semiconductor thin film 130 on the backside of the crystalline Si absorb light and generate charges. By a pn junction formed by the n ⁺ layer 122 on the back side of the crystalline Si and the p layer 134 of the narrow gap semiconductor thin film 130, electrons (−carriers) are converted to the n ⁺ layer 122 and holes (+ carriers) are narrow gap semiconductor thin film 130. To the p ⁺ layer 136. Further, the provision of the hetero pn junction makes it possible to increase the generated voltage.
[0052]
opening to connect to the n ⁺ layer 122 (- electrode forming portion) 40 is formed to provide an electrode to be connected to the n ⁺ layer 122 of the light-receiving surface side to the back side. The insulating film 50, the minus fine electrode 62, and the plus fine electrode 66 are the same as those shown in FIG. Although the crystalline Si substrate is of the n-type in the configuration of FIG. 10, a similar configuration can be manufactured by exchanging the p-layer and the n-layer.
[0053]
The operation of the photoelectric conversion element having the basic structure shown in FIG. 10 will be described. Since crystalline Si is used as a substrate, a narrow gap semiconductor layer having fewer defects than when a light transmitting substrate is used is formed. Can be. Therefore, the conversion efficiency can be improved. Further, the cost can be reduced as compared with the back electrode type using the conventional Ge crystal substrate. However, it is more expensive than a substrate such as glass.
[0054]
Thus, according to the photoelectric conversion element shown in FIG. 10, the electrode area can be increased, and a high-performance photovoltaic cell suitable for high light density can be provided at low cost. As a result, when used in a TPV system, it is possible to reduce the cost of the device while increasing the amount of power generated by the TPV system.
[0055]
Here, an example of a specific structure (material configuration) based on FIG. 10 will be described. The anti-reflection film 110 is a multilayer film made of MgF ₂ , ZnS, SiO ₂ , TiO _{2, and the} like. It has the effect of reducing the reflectance. The crystalline Si substrate 120 is polycrystal or single crystal, and has a thickness of about 0.1 to 0.6 mm, a size of about 1 cm × 1 cm to 100 cm × 100 cm (may be circular), and an n-layer carrier concentration of 1 × 10 ¹⁴ to 1 × 10 ¹⁸ cm ⁻³ , and the n ⁺ layer carrier concentration is 1 × 10 ¹⁷ to 1 × 10 ²⁰ cm ⁻³ .
[0056]
The narrow gap semiconductor thin film 130 is made of carbon (C), AlGaAs, CdSe, CdTe, amorphous Si (a-Si), SiGaAs, InP, AlGaAs, GaInP, InGaAs, Ge, PbS, InAs, InSb, etc., and has a band gap. About 0.2 to 1.6 eV, thickness 0.2 to 30 μm, p-layer carrier concentration 1 × 10 ¹⁴ to 1 × 10 ¹⁸ cm ⁻³ , p ⁺ layer carrier concentration 1 × 10 ¹⁷ to 1 × 10 ²⁰ cm ⁻³ Having.
[0057]
In the opening 40 connected to the Si n ⁺ layer 122, the upper width is about 1 to 50 μm, and the lower width is about 5 to 200 μm. The fine electrodes 62 and 66 are made of Al, Ag, Pd, Ti, Au, Cu, Ni, Cr, or the like.
[0058]
【The invention's effect】
As described above, according to the present invention, there is provided a low-cost, high-performance photoelectric conversion element (photocell) having an electrode structure for realizing a thin-film photovoltaic cell without using a transparent electrode which is a problem in terms of performance improvement. Is done. In addition, a structure on the light receiving surface side that can reduce defects at the semiconductor interface in such a photoelectric conversion element (photovoltaic cell) is provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a conventional thin-film photoelectric conversion element using a light-transmitting substrate.
FIG. 2 is a sectional view showing a first embodiment of a photoelectric conversion element according to the present invention.
FIG. 3 is a sectional view showing a second embodiment of the photoelectric conversion element according to the present invention.
FIG. 4 is a sectional view showing a third embodiment of the photoelectric conversion element according to the present invention.
FIG. 5 is a diagram schematically illustrating a structure in which a dangling bond at an interface of a semiconductor layer is bonded to hydrogen or halogen.
FIG. 6 is a perspective view showing a line-shaped opening for forming a negative electrode connected to the n ⁺ layer.
FIG. 7 is a perspective view showing a dot-shaped opening for forming a minus electrode connected to the n ⁺ layer.
FIG. 8 is a perspective view showing a two-layer electrode structure of the back electrode type thin film photoelectric conversion element.
FIG. 9 is a partially exploded perspective view illustrating a two-layer electrode structure for convenience.
FIG. 10 is a sectional view showing a fourth embodiment of the photoelectric conversion element according to the present invention.
[Explanation of symbols]
Reference Signs List 10 multilayer light control thin film 20 light transmitting substrate 30 semiconductor layer 30a light receiving surface side interface 32 of semiconductor layer 30 n ⁺ layer 34 p layer 36 p ⁺ layer 40 opening (-electrode forming portion)
50 insulating film 60 transparent electrode 61 metal electrode 62 minus fine electrode 66 plus fine electrodes 70 and 170 defect reduction film 80 second insulating film 92 minus collective electrode 96 plus collective electrode 110 anti-reflection Film 120: crystalline Si substrate 122: crystalline Si back side n ⁺ layer 130: narrow gap semiconductor thin film 134: p layer of narrow gap semiconductor thin film 130 136: p ⁺ layer of narrow gap semiconductor thin film 130

Claims (7)

A light-transmitting substrate;
A semiconductor layer formed of a plurality of p-layers or n-layers on the back side of the light-transmitting substrate, and for generating and collecting carriers;
The semiconductor layer is provided in an opening formed in the semiconductor layer and connected to the layer closest to the light receiving surface of the semiconductor layer. A first back electrode not connected to the layer;
A second back surface electrode connected to the most back side layer of the semiconductor layer;
A photoelectric conversion element comprising: The photoelectric conversion element according to claim 1, wherein the opening is formed to be wider toward a rear surface. The photoelectric conversion element according to claim 1, wherein a defect reduction film is provided between the light transmitting substrate and the semiconductor layer. 4. The photoelectric conversion element according to claim 1, wherein the defect reduction film contains hydrogen or a halogen element. 5. The photoelectric conversion element according to claim 1, wherein the opening is formed in a line shape or a dot shape. The photoelectric conversion element according to any one of claims 1 to 5, further comprising a collective electrode via a second insulating film. The photoelectric conversion element according to any one of claims 1 to 6, further comprising a semiconductor substrate containing silicon as a main component instead of the light-transmitting substrate.

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