JP2002208718A - Photovoltaic element and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress reduction of power loss in a photovoltaic element comprising a transparent electrode layer, a photovoltaic conversion layer, a first rear surface electrode layer, an insulation layer, and a second rear surface electrode layer formed from the light incident side wherein the transparent electrode layer has an electric continuity with the second rear surface electrode layer through holes. SOLUTION: Two kinds of through hole having different sizes, i.e., large through holes 66b and small through holes 66a, are made and at least one small through hole 66b is located in a triangular area defined by a large through hole 66b and two adjacent large through holes 66b thus preventing defective parts, where a sufficient film thickness can not be ensured on the inner wall face of the through hole and a transparent electrode layer 63 does not come into electrical contact with a second rear surface electrode layer 65, from concentrating at a part of a photovoltaic element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a photovoltaic element and a solar cell module. More specifically, by providing two types of through holes having different sizes, a sufficient film thickness cannot be secured on the inner wall surface of the through hole, and the transparent electrode layer and the second back electrode layer are not in electrical contact with each other. The present invention relates to a photovoltaic element in which a defective portion is prevented from being concentrated on a part of the photovoltaic element and increasing power loss, and a solar cell module using the same.

[0002]

2. Description of the Related Art In recent years, due to depletion of fossil fuels and environmental problems caused by using fossil fuels, solar energy has attracted attention as next-generation clean energy.

[0003] Many of the photovoltaic elements currently used are:
Electrodes are provided on the light receiving surface side and the non-light receiving surface side of the photoelectric conversion layer, a transparent electrode that transmits light on the light receiving surface side of the photoelectric conversion layer, and a metal electrode is provided on the non-light receiving surface side of the photoelectric conversion layer. Have been.

A transparent electrode that transmits light has a higher electric resistance than a metal electrode, and causes a power loss when a current flows through the transparent electrode. Therefore, a grid electrode intended to reduce the power loss due to the transparent electrode is used. Has been used together. However, since the grid electrode blocks a part of the sunlight incident on the photoelectric conversion layer, there is a new problem that a power loss occurs due to the shadow of the grid electrode.

[0005] Therefore, many research institutes are currently conducting research and development on a photovoltaic element capable of minimizing power loss generated in a transparent electrode and omitting a grid electrode. JP-A-8-64850 discloses that a metal substrate provided with a plurality of through holes is used as a first back electrode layer, and the metal substrate is provided with an insulating layer, a photoelectric conversion layer, a transparent electrode layer, and a second back electrode. A photovoltaic element in which layers are sequentially stacked has been proposed, in which a transparent electrode layer provided on a light receiving surface side of a metal substrate and a second back electrode layer provided on a non-light receiving surface side are electrically connected through through holes. It has a structure connected to. Thereby, the charge generated on the light receiving surface of the photoelectric conversion layer flows from the transparent electrode layer to the second back electrode layer through the through-hole, so that the grid electrode can be omitted, and power loss due to the shadow of the grid electrode is eliminated. There is an advantage.

[0006]

However, since the opening area of the through hole is small, a sufficient film thickness cannot be secured on the inner wall surface of the through hole, and the transparent electrode layer and the second back electrode layer are electrically contacted. There is a high possibility that a part that does not exist will occur. When such a defective portion occurs intensively in a part of the photovoltaic element, a problem occurs that a current generated in the photoelectric conversion layer travels a longer distance in the transparent electrode layer and causes an increase in power loss. .

[0007] Further, the provision of the through-holes causes a problem that the area of the ineffective portion which does not contribute to the power generation increases and the power generation amount decreases. In order to reduce the power loss due to the reduction in the area of the power generation unit, it is conceivable to reduce the radius of the through-hole.However, when the radius of the through-hole is reduced, the interval between the through-holes is increased, so that a general metal electrode and In comparison, the power loss generated in the transparent electrode layer having a higher resistivity is increased. Conversely, in order to reduce the power loss generated in the transparent electrode layer, it is conceivable to reduce the interval between the through holes.However, if the interval between the through holes is reduced, the number of the through holes per area increases, so that power generation is performed. The power loss due to the reduced area of the part increases. In other words, in order to minimize the power loss of the photovoltaic element, the radius of the through-hole and the distance between the through-holes at which the sum of the power loss due to the reduced area of the power generation unit and the power loss generated in the transparent electrode layer is minimized Need to recognize.

The present invention has been devised in order to solve the above-mentioned problems, and a sufficient film thickness cannot be secured on the inner wall surface of the through hole, and the transparent electrode layer and the second back electrode layer are electrically connected. It is an object of the present invention to provide a photovoltaic element and a solar cell module in which non-contact defective portions are prevented from being concentrated on a part of the photovoltaic element, and power loss is reduced.

[0009]

The configuration of the present invention which has been made to achieve the above object is as follows.

That is, the photovoltaic element of the present invention has at least a transparent electrode layer, a photoelectric conversion layer, a first back electrode layer, an insulating layer, and a second back electrode layer from the light incident side. In the photovoltaic element in which the layer and the second back electrode layer are electrically connected via the through hole, the through hole is at least two kinds of large through holes A having different sizes and a small through hole B.
And has at least one small through hole B in a triangular region formed by the other two large through holes A adjacent to the large through hole A.

According to the photovoltaic element of the present invention, at least one small through-hole B is provided in a triangular region formed by the other two large through-holes A adjacent to the large through-hole A. Accordingly, even if a sufficient thickness cannot be secured on the inner wall surface of one small through-hole B and a portion where the transparent electrode layer and the second back electrode layer are not electrically in contact with each other occurs, a nearby large hole may be formed. Electricity can flow between the transparent electrode layer and the second back electrode layer through the through hole A. In other words, a sufficient film thickness cannot be secured on the inner wall surface of the through hole, and a portion where the transparent electrode layer and the second back electrode layer are not in electrical contact is intensively generated in a part of the photovoltaic element. Can be effectively prevented, and an increase in power loss can be minimized.

In addition, the current generated in the photoelectric conversion layer is caused to flow from the transparent electrode layer to the second back electrode layer or from the second back electrode layer to the transparent electrode layer through the through-hole, so that the light receiving surface of the photovoltaic element is formed. Can remove the grid electrode from the
The loss due to the shadow of the electrode itself can be eliminated.

In the photovoltaic device of the present invention, a small through hole B is provided at the center of gravity of a triangular region formed by the other two large through holes A adjacent to the large through hole A; It is preferable that the triangular region formed by the other two large through holes A adjacent to the large through hole A is an equilateral triangle. According to this configuration, when a defect occurs in the small through hole B formed in the above-described triangular region, the distance from the defective portion to the large through hole A can be prevented from becoming extremely long, and power loss can be prevented. Can be more effectively suppressed.

The small through hole B has a substantially circular shape when viewed from the main surface side, and the sheet resistance of the transparent electrode layer of the photovoltaic element is R (Ω). When the maximum output operation current of the power element is Ipm (A / cm ² ), the maximum output operation voltage of the photovoltaic element is Vpm (V), and the interval between the small through holes B is d (mm), the through hole is small. The radius r (μm) of B is

[0015]

(Equation 2) It is preferable to satisfy the following. Here, the reference state is the temperature:
25 ° C., spectral distribution: AM1.5 global solar standard sunlight, irradiance: 1000 W / m ² .

The above formula is derived from the formula for calculating the power loss due to the reduction in the area of the power generation unit and the power loss generated in the transparent electrode layer.

That is, the radius of the small through hole B is defined as r (μ
m), when the distance between the small through holes B is d (mm), the power loss L1 caused by the decrease in the area of the photoelectric conversion layer
Is

[0018]

(Equation 3) Is represented by

On the other hand, in order to determine the power loss occurring in the transparent electrode layer, one triangle is taken out as shown in FIG.
The triangle was divided into n equal parts.

The height of the m-th triangle from the left is h, the width of the bottom is w, the sheet resistance of the transparent electrode layer is R (Ω), and the maximum output operating current of the photovoltaic element measured in the reference state is Ip
m (A / cm ² ), the current value I (x) passing through the hatched portion of the m-th triangle is

[0021]

(Equation 4) The resistance value R (x) of the hatched portion of the m-th triangle is

[0022]

(Equation 5) Therefore, the power consumption L (x) generated in the hatched portion of the m-th triangle is

[0023]

(Equation 6) Is required.

When this formula is integrated to obtain the sum of the power consumption of a triangle divided into n equal parts, the power loss occurring in the transparent electrode layer is obtained.

[0025]

(Equation 7) Is found. Here, Vpm is the maximum output operating voltage of the photovoltaic element. Further, a graph of this equation was created, and the following approximate equation was obtained geometrically.

[0026]

(Equation 8)

FIG. 2 is a graph plotting the exact solution L2 and the approximate value L2 '. From FIG. 2, the exact solution L2 and the approximate value L
2 'has a correlation. Therefore, the power loss generated in the electromotive element can be obtained by L1 + L2 ′, and the radius r of the through-hole at which the power loss is minimum is

[0028]

(Equation 9) Can be obtained by The radius of the small through hole B is +10
Even if it is changed in the range of% to -10%, the influence on the power loss is very small, and therefore, the present invention has a range of ± 10% in the above equation.

By providing a small through-hole B so as to satisfy the above equation, the total of the power loss caused by the transparent electrode layer and the power loss caused by the decrease in the area of the photoelectric conversion layer can be minimized. Thus, power loss generated in the photovoltaic element can be reduced.

In the photovoltaic device of the present invention,
It is preferable to form a back reflection layer between the first back electrode layer and the photoelectric conversion layer. According to such a configuration, light that has not been completely absorbed by the photoelectric conversion layer can be reflected again on the photoelectric conversion layer, and sunlight can be used more effectively.

The first back electrode layer is a conductive substrate having a through hole, and includes a transparent electrode layer, a photoelectric conversion layer, an insulating layer,
It is also preferable that the second back electrode layer is formed continuously from each forming surface to at least a part of the inner wall surface of the through hole. By forming each layer on the conductive substrate in which the through-hole is provided in advance in this way, there is no possibility that any layer is damaged in the step of forming the through-hole, and the yield can be improved.

Preferably, at least a portion of the photoelectric conversion layer is formed continuously over at least a portion of the non-light-receiving surface side surface of the conductive substrate via the inner wall surface of the through hole.
According to such a configuration, even if the transparent electrode layer formed on the light receiving surface side of the photoelectric conversion layer is formed from the main surface to the deep portion of the through hole, the transparent electrode layer and the conductive substrate are electrically connected by the photoelectric conversion layer. It effectively prevents that.

It is more preferable that burrs or burrs generated due to the formation of the through holes in the conductive substrate are disposed mainly on the non-light receiving surface side. As a reason,
The thin film composition is less likely to be deposited at the burrs, and there are portions where the film thickness is thinner than other portions, and portions where the film is not formed (pinholes). However, the performance of the photovoltaic element is the highest priority item, and the thickness of the photoelectric conversion layer and the transparent electrode layer provided on the light receiving surface side of the conductive substrate determines the conversion efficiency of the solar cell. Therefore, as a measure for preventing short-circuit defects, the film thickness cannot be increased. Therefore, by forming a thick film, burrs are arranged on the non-light receiving surface side of the conductive substrate on which the insulating layer and the second back electrode layer are provided so as not to cause a decrease in the conversion efficiency of the solar cell. Prevents short circuit defects from occurring.

The large through-holes A and B have a substantially circular shape when viewed from the light incident surface side, and the thickness of the conductive substrate is T, and the diameter of the small through-hole B is D. When T
/ D is preferably 1 or less. This is because, when the opening area of the through hole is smaller than the depth of the through hole, the thin film composition hardly reaches the deep part of the through hole, the thin film composition to be deposited is small, and as a result, a sufficient film thickness cannot be secured. This is to prevent the problem from occurring.

Preferably, at least a part of the back reflection layer is formed continuously over at least a part of a non-light receiving surface side surface of the conductive substrate via an inner wall surface of the through hole. According to such a configuration, burrs generated on the non-light receiving surface side of the conductive substrate can be covered with the back reflection layer, and the unevenness of the burrs is smoothed, and the layer is not formed to a sufficient thickness at the location where the burrs are generated, resulting in short circuit The occurrence of defects can be effectively prevented.

It is also preferable that the back reflection layer is constituted by a metal layer and a semiconductor layer.

Further, the photovoltaic device of the present invention is characterized in that “the photoelectric conversion layer has any one of a PN junction, a PIN junction, a hetero junction, and a Schottky barrier”;
Amorphous, crystalline, or a mixture thereof "," the photoelectric conversion layer is made of an amorphous silicon-based semiconductor, a microcrystalline silicon-based semiconductor, a polycrystalline silicon-based semiconductor, or a polycrystalline compound-based semiconductor. Or any one of them. "

Further, a solar cell module according to the present invention is characterized in that at least a part of the photovoltaic element according to the present invention is covered with an environment-resistant covering material. As a result, the photovoltaic element can be given properties such as heat resistance, weather resistance, and insulation resistance, and as a result, the reliability of the photovoltaic element is improved.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the photovoltaic device of the present invention will be described below in detail, but the present invention is not limited to the following embodiments.

FIG. 3A shows a photovoltaic element showing an example of the present invention viewed from the light receiving surface side, and FIG. 3B shows a cross-sectional view in which the through-hole portion is enlarged.

The photovoltaic element 30 of the present example has a transparent electrode layer 34, a photoelectric conversion layer 33,
2. The layer structure includes a first back electrode layer 31, an insulating layer 35, and a second back electrode layer 36. However, the back reflection layer 32 is not essential in the present invention.

The photovoltaic element 30 of the present invention is provided with two types of large through holes A having different sizes and a small through hole B, and the other two large through holes A adjacent to the large through hole A. At least one small through-hole B is provided in a triangular region constituted by the through-holes A. With such a configuration, even if a sufficient thickness cannot be secured on the inner wall surface of one small through-hole B and a portion where the transparent electrode layer and the second back electrode layer are not in electrical contact occurs, Electricity can flow between the transparent electrode layer and the second back electrode layer through the large through hole A nearby. In other words, a sufficient film thickness cannot be secured on the inner wall surface of the through hole, and a portion where the transparent electrode layer and the second back electrode layer are not in electrical contact is intensively generated in a part of the photovoltaic element. Can be effectively prevented.

In the photovoltaic element 30 of this embodiment, the triangular area formed by the large through hole A and the other two large through holes A is an equilateral triangle. Further, the shape of the small through hole B as viewed from the main surface side is circular, the sheet resistance of the transparent electrode layer of the photovoltaic element is R (Ω), and the maximum output of the photovoltaic element measured in a reference state. The operating current is Ipm (A
/ Cm ² ), and the maximum output operating voltage of the photovoltaic element is Vpm
(V) When the interval between the small through holes B is d (mm), the radius r (μm) of the small through hole B is

[0044]

(Equation 10) Meets. By providing a small through-hole B so as to satisfy the above equation, the total of the power loss generated in the transparent electrode layer and the power loss generated by the reduction in the area of the photoelectric conversion layer can be minimized. Power loss generated in the power element can be reduced.

The transparent electrode layer 34 and the second back electrode layer 36
Are electrically in contact with each other on the inner wall surface of the through hole 37, and the current generated in the photoelectric conversion layer 33 passes through the inner wall surface of the through hole 37 from the transparent electrode layer 34 to the second back electrode layer 3.
6 or the second back electrode layer 36 flows to the transparent electrode layer 34, so that the grid electrode is not required and the loss due to the shadow of the grid electrode is eliminated.

In order to prevent the current generated in the photoelectric conversion layer 33 from being short-circuited, an electrode composed of the transparent electrode layer 34 and the second back electrode layer 36, the back reflection layer 32 and the first back electrode The electrodes composed of layer 31 are not in electrical contact.

(First Backside Electrode Layer) First Backside Electrode Layer 3
Reference numeral 1 denotes a collecting electrode provided for collecting charges generated on the non-light receiving surface side of the photoelectric conversion layer 33. Specific materials include metals such as Al, Ag, Au, Cu, Ti, Ta, and W, but are not limited thereto. As a method for forming the first back electrode layer, a chemical vapor deposition method, a sputtering method, or the like is suitably used.

As the first back electrode layer 31, a conductive substrate having a function as a support substrate for supporting each layer so that the layers are not damaged by an externally applied force is preferably used. As a specific material of the conductive substrate, F
e, Ni, Cr, Al, Mo, Au, Nb, Ta, V,
Examples include, but are not limited to, thin plates of metals such as Ti, Pt, and Pb or alloys thereof and composites thereof.

The surface of the conductive substrate used as the first back electrode layer 31 may be a smooth surface or a fine uneven surface. In the case of a minute uneven surface, the uneven shape is preferably spherical, conical, or pyramidal, and the maximum value Rmax of the height difference between the peaks and valleys of the unevenness is preferably 0.05 μm to 2 μm. Accordingly, when the back surface reflection layer is not provided on the conductive substrate, light reflection on the uneven surface of the conductive substrate becomes irregular reflection, thereby increasing the optical path length of the reflected light. The thickness of the conductive substrate is usually 10 μm or more from the viewpoint of the production and handling of the substrate, the mechanical strength, and the like.

It is more preferable to use a flexible metal as the conductive substrate because the photovoltaic element can have flexibility.

(Through Hole) The through hole 37 is formed so that the charge generated by the light absorption of the photoelectric conversion layer passes through the transparent electrode layer having a high resistance by a minimum necessary distance, and the second hole having a high electrical conductivity is formed. It has a function as a bypass for reaching the back electrode layer.

FIG. 4 shows the relationship between the layer thickness ratio (layer thickness at the center of the inner wall of the through hole / layer thickness at the main surface) of the layer formed by the sputtering method and the aspect ratio (T / D) of the through hole. In the present invention, when the thickness of the conductive substrate used as the first back electrode layer 31 is T and the hole diameter of the through hole is D, it is preferable to form the through hole such that T / D is 1 or less. This is because, when a layer is continuously formed from the main surface to the inner wall surface of the through-hole by the sputtering method, as shown in FIG. This is for securing at the center of the inner wall.

As a method for forming a through hole in the conductive substrate, a mechanical processing method such as press working, sand blasting, or the like, or a processing method using an energy beam such as a laser beam, an ion beam, or an electron beam. And a chemical processing method such as etching processing, but are not limited thereto.

In the photovoltaic element according to the present invention, the photovoltaic element is not capable of securing a sufficient film thickness on the inner wall surface of the through hole and the transparent electrode layer and the second back electrode layer are not in electrical contact with each other. Two types of large through-holes A and small through-holes B having different sizes are formed in order to prevent intensive occurrence in a part of the element. On the inner wall surface of the large through-hole A, the area of the large through-hole A as viewed from the light incident side is reduced so that a defective portion where the transparent electrode layer and the second back electrode layer are not in electrical contact does not occur. , At least 20% of the area of the small through hole B
It is preferable that it is formed larger than the above.

(Back Reflection Layer) The back reflection layer 32 retransmits the light that could not be absorbed by the photoelectric conversion layer 33 again.
It has a role as a light reflection layer that reflects light. The back reflection layer 32 used in the present invention is located between the first back electrode layer 31 and the photoelectric conversion layer 33.

As the material of the back reflection layer, Au, Ag,
Cu, Al, Ni, Fe, Cr, Mo, W, Ti, C
Metals such as o, Ta, Nb, and Zr, and alloys such as stainless steel are mentioned, and metals having high reflectivity such as Al, Cu, Ag, and Au are particularly preferable.

The shape of the back surface reflection layer may be flat, but it is more preferable that the back surface reflection layer has an uneven shape for scattering light. By having an uneven shape that scatters light, it scatters long wavelengths that could not be absorbed by the photoelectric conversion layer, extends the optical path length in the photoelectric conversion layer, improves the long wavelength sensitivity of the photovoltaic element, and short-circuits The current can be increased and the photoelectric conversion efficiency can be improved. The uneven shape that scatters light has a maximum value Rmax of the difference between the heights of peaks and valleys of the unevenness of 0.2 μm or more.
It is preferably 2.0 μm.

The back reflection layer can be formed by an evaporation method, a sputtering method, a plating method, a printing method, or the like. Furthermore, in order to form irregularities that scatter light on the back reflection layer,
The formed metal or alloy film may be subjected to processing such as dry etching, wet etching, sand blast, and heating. In addition, the above-described metal or alloy can be deposited while heating the substrate to form an uneven shape that scatters light. In addition, by forming a semiconductor layer such as ZnO on the formed metal or alloy film, unevenness for scattering light can be formed on the back reflection layer.

(Photoelectric Conversion Layer) The photoelectric conversion layer 33 converts light into electricity.
It has a function to change the light, and the non-light receiving of the transparent electrode layer 34
It is provided on the surface side. As a material of this photoelectric conversion layer,
Group IV elements such as Si, C, Ge, etc .;
Group IV element alloy, GaAs, InSb, GaP, GaS
b, III-V compounds such as InP, InAs, ZnS
e, CdTe, ZnS, CdS, CdSe, CdTe, etc.
II-VI compound of the formula CuInSe _TwoI-III
-VI compounds, but are not limited thereto.
Absent. Among the above materials, particularly preferred for the photoelectric conversion layer of the present invention.
Suitable materials include a-Si: H (hydrogenated ammonia).
Rufas silicon), a-SiGe: H, a-SiC:
And a group IV element such as H. This is because these materials
Has relatively high physical properties such as band gap and Fermi level.
Easy to control and change the characteristic value of photovoltaic element
This is because it is considered suitable.

The photoelectric conversion layer forms at least one set of a pn junction, a pin junction, a hetero junction, or a Schottky barrier. As a preferable method for forming the photoelectric conversion layer, microwave plasma CVD, VHF plasma CVD, etc.
And various chemical vapor deposition methods such as an RF plasma CVD method.

(Transparent Electrode Layer) The transparent electrode layer 34 transmits light.
The electrode on the incident side of light passing through and the film thickness is optimized
By doing so, it also plays a role as an antireflection film. Transparent
The bright electrode layer is in a wavelength region where the photoelectric conversion layer can absorb light.
Require high transmittance and low resistivity
It is. Specifically, the transmittance at 600 nm is 90%.
It is preferable that it is above. Also, the resistivity is preferable
Is 5 × 10^-3Ωcm or less, more preferably 1 × 10
^-3Ωcm or less. The material is In_TwoO_Three, S
nO_Two, ITO (In_TwoO_Three+ SnO_Two), ZnO, Cd
O, Cd_TwoSnO_Four, TiO_Two, Ta _TwoO_Five, Bi_TwoO_Three, M
oO_Three, Na_XWO_ThreeOr conductive oxides such as
A mixture is preferably used. In addition, these compounds
Adds an element (dopant) that changes electrical conductivity to a product
You may.

For example, when the transparent electrode layer is made of ZnO, Al, In, B, G
When a, Si, F, etc. are In ₂ O ₃ , Sn,
F, Te, Ti, Sb, Pb, etc., and in the case of SnO ₂ , F, Sb, P, As, In, Ti, Te, W, C
1, Br, I and the like are preferably used.

As a method of forming the transparent electrode layer, a method of forming by sputtering with a sputtering gas containing a trace amount of oxygen is preferably used.

(Insulating Layer) The insulating layer 35 is provided between the first back electrode layer 31 and the second back electrode layer 36, and the first back electrode layer 31 and the second back electrode layer 36 are electrically connected. Electrical insulation is maintained.

As a typical material of the insulating layer, SiO ₂ ,
Si ₃ N ₄ , MgF ₂ , Al ₂ O ₃ , TiO ₂ , ZnS, Ce
Inorganic materials such as F ₃ and ZrO ₂ are preferably used, and examples of the forming method include a chemical vapor deposition method, a sputtering method, a vacuum deposition method, and an electrolytic deposition method.

In addition to the inorganic material, the insulating layer can be formed using a polymer resin such as polyester, ethylene-vinyl acetate copolymer, acrylic resin, epoxy resin and urethane.

As a method of forming an insulating layer using a polymer resin, for example, a method of dissolving in a solvent for spin coating or dipping, a method of melting with heat and coating with a roller, a method of depositing by electrolytic polymerization, a method of electrodeposition, Deposition method, a method by plasma polymerization, and the like, which are appropriately determined from various conditions such as the physical properties of the polymer resin and a desired film thickness. From the viewpoint of mass productivity, dipping, roller coating, and electrodeposition. And the like are preferred.

The thickness of the insulating layer is such that there is no pinhole,
It is determined from requirements such as a sufficient barrier property against humidity, adhesion and flexibility, but if it is 1 μm or less, it tends to become a pinhole, and if it is 30 μm or more, flexibility is impaired, so that about 1 to 30 μm is preferable.

(Second Backside Electrode Layer) Second Backside Electrode Layer 3
Reference numeral 6 denotes a current collecting electrode provided to collect electric charges generated on the light receiving surface side of the photoelectric conversion layer through the through hole 37.
As specific materials, Al, Ag, Au, Cu, Ti, T
Examples include metals such as a and W, but are not limited thereto. As a method for forming the back electrode layer, a chemical vapor deposition method, a sputtering method, or the like is suitably used.

(Solar Cell Module) FIG. 5 (a) is a schematic perspective view showing an example of the solar cell module of the present invention, and FIG. 5 (b) is a sectional view taken along line AA in FIG. 5 (a). It is.

As shown in the figure, the solar cell module of the present invention comprises a photovoltaic element 50 of the present invention and a coating material 51 having environmental resistance. The photovoltaic elements are electrically connected to each other, and the light receiving surface side and the non-light receiving surface side of the photovoltaic element are covered with two coating materials.
As a material of the coating material, a glass plate, a fluororesin, an acrylic resin, polyethylene terephthalate, polypropylene or the like is preferably used, but is not limited thereto.

[0072]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Embodiment 1) FIG. 6A is a view of the photovoltaic device according to the first embodiment of the present invention as viewed from the light receiving surface side, and FIG. FIG. 6B is an enlarged schematic diagram of the portion.
FIG. 6C shows a cross-sectional view of the through hole.

The photovoltaic element 67 of this embodiment includes a transparent electrode layer 63, a photoelectric conversion layer 62, and a back reflection layer 6 from the light incident side.
1, a first back electrode layer 60, an insulating layer 64, and a second back electrode layer 65.

The first back electrode layer 60 has a thickness of 150 μm.
And a plurality of through holes 66 are provided. The sheet resistance of the transparent electrode layer 63 is 30 (Ω), the maximum output operating current of the photovoltaic element measured in the reference state is 0.0147 (A / cm ² ), and the maximum output operating voltage of the photovoltaic element is 1 .2 (V), the interval between the through holes is 6 (mm).

As shown in FIG. 6B, two types of through holes 66a and 66b having different radii are provided in the photovoltaic element of this embodiment.
Are provided, and the radius of the small through hole 66a is 300 μm.
m, the radius of the larger through hole 66b is 400 μm. The triangular region formed by the large through hole 66b and the other two large through holes 66b is a regular triangle, and the small through hole 66a is located at the center of gravity of the regular triangular region.
Is provided.

Large through hole 66b and small through hole 66
a is formed by a YAG laser. YAG lasers have excellent light-collecting characteristics due to their short oscillation wavelength, and
Because of its excellent absorption properties to metals, it is ideal for fine drilling of stainless steel. YA when forming through holes
The average output of the G laser is 200W.

The back reflection layer 61 is composed of the ZnO layer 61a and the A
The first back electrode layer 60 provided with the through hole 66 is formed continuously from the main surface on the light receiving surface side to a part of the inner wall surface of the through hole. Back reflection layer 6
1 was formed by using a sputtering method. After Al was deposited on the first back electrode layer to a thickness of 500 nm at room temperature, Z was deposited.
nO is deposited to a thickness of 2 μm at a substrate temperature of 200 ° C.

The photoelectric conversion layer 62 is made of P-type, I-type, or N-type amorphous silicon, and extends from the main surface on the light-receiving surface side of the back reflection layer 61 to the main surface on the non-light-receiving surface side through the inner wall surface of the through hole. Are formed continuously over a part of each.

The photoelectric conversion layer 62 is formed by plasma CV
Using a D device, an N-type amorphous silicon layer 62a, an I-type amorphous silicon layer 62b, and a P-type amorphous silicon layer 62
They are formed in the order of c.

(Formation of N-type Amorphous Silicon Layer) H ₂ gas was introduced into the deposition chamber, and the flow rate was adjusted with a mass flow controller to 50 sccm. Adjust so that The heater was set so that the substrate temperature became 220 ° C., and when the substrate temperature was stabilized, SiH ₄ gas, PH ₃
/ H ₂ gas is introduced into the deposition chamber. At this time, the flow rate of the SiH ₄ gas was 1 sccm, and the flow rate of the PH ₃ / H ₂ gas was _{2.5 s.}
C. The flow rate of H ₂ gas is adjusted to 50 sccm, and the pressure in the deposition chamber is adjusted to about 133 Pa (1 torr). A 13.56 MHz RF power supply is used as the high frequency power supply. The power of the RF power source was set to 2 W, RF power was applied to the RF electrode (high-frequency introduction part), plasma was generated, the shutter was opened, and the formation of an N-type amorphous silicon layer on the ZnO layer 61a was started. When the layer thickness reaches 10 nm, the shutter is closed, the RF power is turned off to extinguish the plasma, and the formation of the N-type amorphous silicon layer is completed.
SiH ₄ gas into the deposition chamber, stopping the flow of PH ₃ / H ₂ gas, after continued to flow H ₂ gas to 5 minutes deposition chamber, stopping the inflow of the H ₂ gas, about the deposition chamber and the gas pipe 1 .33 ×
The chamber is evacuated to 10 ⁻³ Pa (1 × 10 ⁻⁵ torr).

(Formation of I-Type Amorphous Silicon Layer) H ₂ gas was introduced into the deposition chamber, and the flow rate was adjusted to 100 sccm by a mass flow controller, and the pressure in the deposition chamber was set to about 67 Pa (0.5 torr). Adjust so that The heater is set so that the temperature of the substrate becomes 250 ° C., and when the substrate temperature is stabilized, SiH ₄ gas is introduced into the deposition chamber. At this time, the flow rate of the SiH ₄ gas is ₄ sc
cm, the flow rate of H ₂ gas is adjusted to 100 sccm, and the pressure in the deposition chamber is adjusted to about 67 Pa (0.5 torr). A 13.56 MHz RF power supply is used as the high frequency power supply. The power of the RF power source was set to 3 W, RF power was applied to the RF electrode (high-frequency introduction part), plasma was generated, the shutter was opened, and the I-type amorphous silicon layer was formed on the N-type amorphous silicon layer. Start forming, the layer thickness is 85 nm
Then, the shutter is closed, the RF power is turned off to extinguish the plasma, and the formation of the I-type amorphous silicon layer is completed. Stop the flow of SiH ₄ gas into the deposition chamber, after continued to flow H ₂ gas to 5 minutes deposition chamber, H ₂ flow of gas is also stopped, the deposition chamber and the gas pipe about 1.33 × 10 ^-3 Pa
(1 × 10 ⁻⁵ torr).

(Formation of P-type Amorphous Silicon Layer) H ₂ gas was introduced into the deposition chamber, and the flow rate was adjusted with a mass flow controller to 40 sccm, and the pressure in the deposition chamber was adjusted to about 266 Pa (2.0 torr). Adjust so that The heater was set so that the substrate temperature became 250 ° C., and when the substrate temperature was stabilized, SiH ₄ / H ₂ gas,
BF ₃ / H ₂ gas is introduced into the deposition chamber. At this time, SiH
₄ / H ₂ gas flow rate is 0.25 sccm, BF ₃ / H ₂ gas flow rate is ₂ sccm, H ₂ gas flow rate is 40 sccm,
The pressure in the deposition chamber is adjusted to about 266 Pa (2.0 torr). 13.56 MH as high frequency power supply
z RF power supply is used. The power of the RF power source was set to 40 W, RF power was applied to the RF electrode (high-frequency introduction part), plasma was generated, the shutter was opened, and the P-type amorphous silicon layer was formed on the I-type amorphous silicon layer. When the formation is started, the shutter is closed when the layer thickness becomes 4 nm, and the RF
The power is turned off to extinguish the plasma, and the formation of the P-type amorphous silicon layer is completed. SiH ₄ / H ₂ gas into the deposition chamber, B
Stopping the inflow of F ₃ / H ₂ gas, after continued to flow H ₂ gas to 5 minutes deposition chamber, H ₂ flow of gas is also stopped, the deposition chamber and the gas pipe about 1.33 × 10 ^-3 Pa ( 1 × 10 ^-5 to
Evacuate to rr).

The transparent electrode layer 63 is made of ITO, and is formed continuously from the main surface on the light receiving surface side of the photoelectric conversion layer 62 to a part of the inner wall surface of the through hole 66. Using a sputtering apparatus, ITO was used as a target, Ar / O ₂ was introduced as a sputtering gas at a rate of 30 sccm / 0.1 sccm, and a power of 200 W was applied from a DC power supply to set the substrate at 20 sc.
While heating to 0 ° C., a 70 nm thick ITO layer is deposited.

The insulating layer 64 is made of Si ₃ N ₄ and has a thickness of 1
The first back electrode layer 60 is formed continuously from the main surface on the non-light receiving surface side to a part of the inner wall surface so as to have a thickness of 5 μm,
The first back surface electrode layer 6 is formed in the inner wall portion of the through hole and the region around the through hole.
The exposed portions of the O and the back reflection layer 61 are completely covered with the insulating layer 64. The insulating layer 64 has a substrate temperature of 2
It is formed at 00 ° C. by a sputtering method.

The second back electrode layer 65 is made of Al.
The insulating layer 64 is formed continuously from the main surface on the non-light receiving surface side to a part of the inner wall surface of the through hole, and is in electrical contact with the transparent electrode layer 63. As a result, the current generated in the photoelectric conversion layer 62 is guided through the through hole, and the grid electrode that blocks light can be omitted. The second backside electrode layer 65 is formed by using a sputtering apparatus and forming Al to a thickness of 10 μm at a substrate temperature of 200 ° C.

As described above, in the photovoltaic element of this embodiment, after forming the through holes in the first back electrode layer, the back reflection layer,
The photoelectric conversion layer, the transparent electrode layer, the insulating layer, and the second back electrode layer are stacked in this order.

(Embodiment 2) A perspective view of a solar cell module according to a second embodiment of the present invention is shown in FIG.
FIG. 7B is a cross-sectional view taken along the line CC in FIG. 7A, and FIG. 7C is an enlarged cross-sectional view of the electrical connection portion of the photovoltaic element in the portion D in FIG. Note that points which are not specially described are the same as in the first embodiment.

The solar cell module according to the present embodiment
Eight photovoltaic elements 70, copper foil 71 for electrically connecting the photovoltaic elements to each other, reinforcing plate 72 made of galvanized steel sheet having a thickness of 400 μm, ethylene-tetrafluoroethylene film (ETFE) having a thickness of 50 μm And a protective film 73 made of a polyethylene terephthalate film having a thickness of 100 μm. Here, an EVA sheet 75 having a thickness of 225 μm is used as an adhesive layer to integrate the photovoltaic element 70, the reinforcing plate 72, the surface protection film 73, and the insulating film 74.

The method for manufacturing a solar cell module can be divided into a step of serializing the photovoltaic elements and a step of coating the serialized photovoltaic elements.

After arranging eight photovoltaic elements in a horizontal line in order to serialize the photovoltaic elements, in the adjacent photovoltaic elements, the first back electrode layer 76 of one element and the other are separated. The second back electrode layer 77 of the element is electrically connected by the copper foil 71. Here, the connection point of the copper foil is a corner of the photovoltaic element, and the first back electrode layer 76 and the copper foil 71, and the second back electrode layer 77 and the copper foil 71 are each made of a conductive adhesive. Connect with When electrically connecting the photovoltaic elements to each other, an insulating layer is formed in a region (corner of the photovoltaic element) where the conductive adhesive is applied so that the copper foil can be easily connected to the first back electrode layer. 78 and the second back electrode layer 77 are 1
It has been removed in a size of cm × 1 cm. This insulating layer 7
Electric discharge machining is used as a method for removing the eighth and second back electrode layers 77.

After the eight photovoltaic elements are serialized, an insulating film 74 is provided on the non-light-receiving side of the photovoltaic element 70, a reinforcing plate 72 is provided on the non-light-receiving side of the insulating film, and a light-receiving element of the photovoltaic element is provided. The surface protection films 73 are arranged on the surface side, respectively.
Vacuum heating is performed using a heavy vacuum laminating apparatus. The preparation conditions at that time are as follows: pumping speed of about 10 ⁴ Pa / sec (7
6 torr / sec), degree of vacuum about 670 Pa (5 torr)
After evacuation in r) for 30 minutes, the laminating apparatus is put into a hot air oven at 160 ° C. and heated for 50 minutes. Thereafter, the laminating apparatus is taken out of the hot-air oven and cooled at room temperature to complete a flat solar cell module.

(Embodiment 3) The photovoltaic element according to Embodiment 3 of the present invention is characterized in that the back reflection layer is made of nickel and formed by plating. By forming the back reflection layer using a plating method, in addition to the main surface on the light-receiving surface side of the first back electrode layer and the inner wall surface of the through-hole, around the through-hole on the non-light-receiving surface side of the first back electrode layer. A layer can also be formed on the main surface of. Thereby, the burr generated on the non-light-receiving surface side of the first back electrode layer at the time of forming the through-hole can be covered, and the unevenness of the burr can be reduced. as a result,
In a later step, a layer is likely to be normally formed at a location where burrs are generated, short-circuit defects are less likely to occur, and the yield is improved. Note that points which are not specially described are the same as in the first and second embodiments.

The nickel plating of the first back electrode layer is performed as follows. First, cathodic electrolytic degreasing is performed at 10 A / dm ² ,
Anode electrolytic degreasing is performed for 5 min at 10 A / dm ² for 2 min, followed by hydrochloric acid washing. Next, after nucleating nickel at 3 A / dm ² for 30 sec in a nickel strike bath, 3 A / dm ² ,
Perform nickel plating for 4 minutes. Thereby, 2 μm
Of nickel is plated.

[0095]

As described above, according to the photovoltaic element of the present invention, at least two types of large through holes A and small through holes B having different sizes are provided, and the large through hole A is adjacent to the large through hole A. By providing at least one small through-hole B in a triangular region formed by the other two large through-holes A, a sufficient film thickness cannot be secured on the inner wall surface of the through-hole, and the transparent electrode layer and It is possible to prevent a defective portion where the second back electrode layer is not in electrical contact from occurring intensively in a part of the photovoltaic element, and to minimize an increase in power loss.

[Brief description of the drawings]

FIG. 1 is a model diagram used to derive a calculation formula for calculating a power loss of a photovoltaic element.

FIG. 2 is a graph comparing an exact solution and an approximate value of a power loss generated in a transparent electrode layer.

FIG. 3 is a plan view of the photovoltaic element according to the embodiment of the present invention viewed from the light receiving surface side and an enlarged sectional view of a through-hole portion.

FIG. 4 is a graph showing a relationship between an aspect ratio of a through hole and a film thickness ratio.

FIG. 5 is a perspective view and a sectional view of a solar cell module according to an embodiment of the present invention.

FIG. 6 is a plan view of the photovoltaic element according to the first embodiment of the present invention viewed from the light receiving surface side and an enlarged cross-sectional view of the through hole.

FIG. 7 is a perspective view, a cross-sectional view, and a cross-sectional view illustrating an electrical connection portion of a photovoltaic element according to a second embodiment of the present invention.

[Explanation of symbols]

 10, 30, 50, 67, 70 Photovoltaic elements 11, 37, 66 Through holes 31, 60, 76 First back electrode layer (conductive substrate) 32, 61, 79 Back reflection layer 33, 62, 700 Conversion layer 34, 63, 701 Transparent electrode layer 35, 64, 78 Insulating layer 36, 65, 77 Second back electrode layer 51 Coating material 61b Al layer 61a ZnO layer 62 a N-type amorphous silicon layer 62b I-type non-type Amorphous silicon layer 62c P-type amorphous silicon layer 71 Copper foil 72 Reinforcement plate 73 Surface protection film 74 Insulation film 75 EVA sheet

Continued on the front page (72) Inventor Meiji Takabayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 5F051 AA05 CA15 CA40 CB27 EA03 FA02 FA03 FA04 FA14 FA15 FA19 FA23 GA02 JA05

Claims (15)

[Claims] (1) a transparent electrode layer at least from a light incident side;
A photovoltaic element having a photoelectric conversion layer, a first back electrode layer, an insulating layer, and a second back electrode layer, wherein the transparent electrode layer and the second back electrode layer are electrically connected to each other through through holes. In the above, the through-hole has at least two kinds of large through-holes A having different sizes and a small through-hole B, and is constituted by the other two large through-holes A adjacent to the large through-hole A. A photovoltaic element having at least one small through-hole B in a triangular region to be formed. 2. The small through hole B is provided at a position of the center of gravity of a triangular area formed by the other large through hole A adjacent to the large through hole A. 3. The photovoltaic device according to claim 1. 3. The photovoltaic device according to claim 1, wherein the triangular region formed by the other large through-hole A adjacent to the large through-hole A is an equilateral triangular region. Power element. 4. The small through hole B has a substantially circular shape when viewed from the main surface side, and the transparent electrode layer of the photovoltaic element has a sheet resistance R (Ω) measured in a reference state. The maximum output operating current of the photovoltaic element is Ipm (A / cm ² ),
When the maximum output operation voltage of the photovoltaic element is Vpm (V) and the interval between the small through holes B is d (mm), the radius r (μm) of the small through hole B is 4. The photovoltaic device according to claim 1, wherein 5. The photovoltaic device according to claim 1, wherein a back reflection layer is formed between the first back electrode layer and the photoelectric conversion layer. 6. The first back electrode layer is a conductive substrate having a through hole, and the transparent electrode layer, the photoelectric conversion layer, the insulating layer, and the second back electrode layer are formed on the inner wall of the through hole from the respective forming surfaces. The photovoltaic device according to any one of claims 1 to 4, wherein the photovoltaic device is formed continuously over at least a part of the surface. 7. At least a part of the photoelectric conversion layer is formed continuously over at least a part of a non-light-receiving surface side surface of the conductive substrate via an inner wall surface of the through hole. Item 7. A photovoltaic element according to Item 6. 8. The method according to claim 6, wherein burrs or burrs generated due to the formation of the through holes in the conductive substrate are arranged so as to mainly come to the non-light receiving surface side. The photovoltaic device according to any one of the preceding claims. 9. The large through hole A and the small through hole B
Has a substantially circular shape when viewed from the light incident surface side, and when the thickness of the conductive substrate is T and the hole diameter of the small through hole B is D, T / D is 1 or less. The photovoltaic device according to any one of claims 6 to 8, wherein 10. A back reflection layer is formed between the first back electrode layer and the photoelectric conversion layer, and at least a part of the back reflection layer is formed on the conductive substrate via an inner wall surface of a through hole. 10. The photovoltaic device according to claim 6, wherein the photovoltaic device is formed continuously over at least a part of the non-light receiving surface side surface of the photovoltaic device. 11. The back reflection layer is composed of a metal layer and a semiconductor layer.
3. The photovoltaic device according to claim 1. 12. The photoelectric conversion layer is a PN junction, a PIN
The photovoltaic device according to claim 1, wherein the photovoltaic device has one of a junction, a heterojunction, and a Schottky barrier. 13. The photoelectric conversion layer according to claim 1, wherein the photoelectric conversion layer is amorphous, crystalline,
13. The photovoltaic device according to claim 1, wherein the photovoltaic device is formed of a mixed phase thereof. 14. The semiconductor device according to claim 1, wherein the photoelectric conversion layer is made of any of an amorphous silicon-based semiconductor, a microcrystalline silicon-based semiconductor, a polycrystalline silicon-based semiconductor, and a polycrystalline compound-based semiconductor. 13. The photovoltaic element according to any one of 1 to 12. 15. A solar cell module, wherein at least a part of the photovoltaic element according to claim 1 is covered with an environment-resistant covering material.