JP5980060B2 - Solar cell - Google Patents

Description

  The present invention relates to a solar cell, and particularly to a solar cell including an amorphous oxide semiconductor layer containing In, Ga, and Zn.

In—Ga—Zn—O which is a transparent oxide semiconductor (hereinafter referred to as “InGaZnO amorphous oxide semiconductor”) has a large band gap energy of about 3 eV or more and is formed at room temperature. Even so, it has a higher electron mobility (> 10 cm ² / Vs) than a polycrystalline oxide semiconductor (eg, ZnO). For these reasons, InGaZnO amorphous oxide semiconductors are attracting attention as materials for channel layers of TFTs that drive electronic paper, liquid crystal panels, organic ELs, and the like.

  An InGaZnO amorphous oxide semiconductor, which is such a wide gap material (a material having a large band gap energy), improves open-circuit voltage and reduces optical absorption loss in, for example, a heterojunction solar cell with a p-type silicon substrate. It is also attractive as a material constituting the n-type window layer (for example, Patent Document 1, Patent Document 2, and Non-Patent Document 1).

Patent Document 1 proposes a photoelectric device including a p-type semiconductor substrate and an n-type transparent amorphous oxide semiconductor layer provided on the p-type semiconductor substrate. The p-type semiconductor substrate described in Patent Document 1 is formed of a p-type semiconductor material such as a p-type silicon wafer or a p-type silicon thin film. The n-type transparent amorphous oxide semiconductor layer described in Patent Document 1 mainly includes zinc oxide (ZnO), a mixture of tin oxide and zinc oxide (ZnO—SnO ₂ mixture) or zinc oxide. And a mixture of indium oxide (ZnO—In ₂ O ₃ mixture), and further, aluminum, gallium, indium, boron, yttrium, scandium, fluorine, vanadium, silicon, germanium, zirconium, hafnium, nitrogen and Contains at least one of beryllium.

  Patent Document 2 proposes a photoelectric conversion element in which a p-type silicon layer and an n-type oxide semiconductor layer are stacked. The p-type silicon layer described in Patent Document 2 includes one or more layers selected from a single crystal p-type silicon layer, a polycrystalline p-type silicon layer, and an amorphous p-type silicon layer. The n-type oxide semiconductor layer described in Patent Document 2 includes one or more oxide semiconductors selected from indium oxide, zinc oxide, tin oxide, and gallium oxide.

  Non-Patent Document 1 proposes a heterojunction solar cell in which a layer made of InGaZnO amorphous oxide (InGaZnO amorphous oxide semiconductor layer) is formed on a p-type crystalline silicon layer.

  On the other hand, the electron affinity of the InGaZnO amorphous oxide semiconductor layer whose In: Ga: Zn (atomic ratio) is 1: 1: 1 is larger than the electron affinity of crystalline Si. Therefore, a high open-circuit voltage cannot be obtained in a solar cell including this InGaZnO amorphous oxide semiconductor layer. In Non-Patent Document 1, an InGaZnO amorphous oxide semiconductor layer having a high Ga content is formed on a p-type crystalline silicon layer, which has the characteristics of low electron affinity and high band gap energy in anticipation of a high open circuit voltage. Heterojunction solar cells are proposed.

JP 2009-283886 A JP 2011-86770 A

Kyeongmi Lee, et.al ‘Photovoltaic properties of n-type amorphous In-Ga-Zn-O and p-type single crystal Si heterojunction solar cells: Effects of Ga content’ Thin Solid Films 520 (2012) 3808-3812

  However, an InGaZnO amorphous oxide semiconductor with a high Ga content has many defect levels at the upper end of the valence band (see Non-Patent Document 1). For this reason, when a heterojunction is formed by directly forming an InGaZnO amorphous oxide semiconductor layer having a high Ga content on a p-type crystalline silicon layer, carrier recombination at the heterointerface increases and photoelectric conversion efficiency increases. It becomes a factor to decrease.

  The present invention has been made in view of this point, and the object of the present invention is to suppress carrier recombination at the heterointerface between the silicon layer and the InGaZnO amorphous oxide semiconductor layer having a high Ga content. It is providing the solar cell provided with the simple structure.

  The solar cell includes a p-type silicon layer and two or more amorphous oxide semiconductor layers that are provided on the p-type silicon layer and include In, Ga, and Zn and have different Ga contents. The Ga content in the amorphous oxide semiconductor layer provided on the p-type silicon layer side is lower than the Ga content in the amorphous oxide semiconductor layer provided far from the p-type silicon layer.

The p-type silicon layer is preferably composed of at least one of a single crystal p-type silicon layer, a polycrystalline p-type silicon layer, and an amorphous p-type silicon layer. The thickness of the amorphous oxide semiconductor layer provided on the p-type silicon layer side is preferably 10 nm or less .

  Another InGaZnO amorphous oxide semiconductor layer having a Ga content lower than that of the InGaZnO amorphous oxide semiconductor layer at the hetero interface between the p-type silicon layer and the InGaZnO amorphous oxide semiconductor layer having a high Ga content Thus, a hetero interface is formed by the p-type silicon layer and the InGaZnO amorphous oxide semiconductor layer having a low Ga content. Therefore, since carrier recombination at the heterointerface is suppressed, the photoelectric conversion efficiency is improved in the solar cell of the present invention.

It is sectional drawing which shows an example of a structure of the solar cell of this invention.

  Hereinafter, the solar cell of the present invention will be described in detail with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[Configuration of solar cell]
FIG. 1 is a cross-sectional view showing an example of the configuration of the solar cell of the present invention. In the solar cell 10 shown in FIG. 1, a back electrode 11, a p-type silicon layer 12, and an InGaZnO amorphous oxide semiconductor layer 13 having a low Ga content (simply referred to as “amorphous oxide semiconductor layer 13”). InGaZnO amorphous oxide semiconductor layer 14 with high Ga content (may be simply referred to as “amorphous oxide semiconductor layer 14”), and surface electrode 15. Hereinafter, the configuration of the solar cell 10 will be described.

<Back electrode>
The back electrode 11 is preferably formed on the back side of the p-type silicon layer 12 and made of a metal such as Al. The thickness of the back electrode 11 is not particularly limited.

  The method for forming the back electrode 11 is not particularly limited. For example, the back electrode 11 may be formed by vacuum deposition (for example, resistance heating deposition) using Al metal as a target. The back electrode 11 may be formed by applying a conductive paste containing aluminum powder or the like (eg, screen printing) and then drying at a temperature of 100 to 400 ° C.

<P-type silicon layer>
The p-type silicon layer 12 is preferably composed of at least one of a single crystal p-type silicon layer, a polycrystalline p-type silicon layer, and an amorphous p-type silicon layer. The resistance value, the crystal orientation, the thickness, etc. of the p-type silicon layer 12 are not particularly limited.

<Amorphous Oxide Semiconductor Layers with Different Ga Content>
The amorphous oxide semiconductor layer 13 having a low Ga content is formed on the p-type silicon layer 12, and the amorphous oxide semiconductor layer 14 having a high Ga content is an amorphous oxide having a low Ga content. It is formed on the semiconductor layer 13. The amorphous oxide semiconductor layer 13 having a low Ga content and the amorphous oxide semiconductor layer 14 having a high Ga content are both amorphous oxide semiconductor layers containing In, Ga, and Zn. It is preferable. The Ga content in the amorphous oxide semiconductor layer 13 with a low Ga content is lower than the Ga content in the amorphous oxide semiconductor layer 14 with a high Ga content.

  The amorphous oxide semiconductor layer 14 having a high Ga content has many defect levels at the upper end of the valence band. Therefore, when a heterojunction is formed by directly forming an amorphous oxide semiconductor layer 14 having a high Ga content on the p-type silicon layer 12, carrier recombination at the heterointerface increases and photoelectric conversion efficiency decreases. It becomes a factor to do. On the other hand, the amorphous oxide semiconductor layer 13 with a low Ga content has few defect levels. Therefore, by providing the amorphous oxide semiconductor layer 13 with a low Ga content between the p-type silicon layer 12 and the amorphous oxide semiconductor layer 14 with a high Ga content, carrier recombination at the heterointerface is performed. Is suppressed. Thereby, a good bonding interface is obtained. That is, it is possible to prevent a decrease in photoelectric conversion efficiency in the solar cell 10 that is a product.

  The method for measuring the Ga content in the amorphous oxide semiconductor layer 13 having a low Ga content and the Ga content in the amorphous oxide semiconductor layer 14 having a high Ga content is not particularly limited. Secondary ion mass spectrometry, Auger electron spectroscopy, energy dispersive X-ray spectroscopy, and the like can be given.

  The amorphous oxide semiconductor layer 13 with a low Ga content and the amorphous oxide semiconductor layer 14 with a high Ga content are made of Be, Na, Mg, Al, Si, Ca, Sc in addition to In, Ga, and Zn. , Ti, V, Fe, Co, Ni, Ge, As, Y, Zr, Nb, Mo, Sn, Sb, Ba, Hf, Ta, W, and Pb may be included as an additive element. . Each of the amorphous oxide semiconductor layers 13 and 14 may be a single layer made of a single material, or may be a single layer containing two or more materials having different compositions. Layers made of materials having different compositions may be stacked.

  The thickness of the amorphous oxide semiconductor layer 13 having a low Ga content is preferably 10 nm or less. Thereby, the fall of a short circuit current can be prevented.

  The thickness of the amorphous oxide semiconductor layer 14 having a high Ga content is not particularly limited, but is preferably 10 nm to 1.5 μm.

  A method for forming the amorphous oxide semiconductor layers 13 and 14 is not particularly limited, but a sputtering method is preferable. As a result, the amorphous oxide semiconductor layers 13 and 14 that are flat at the atomic level and have a thickness of nano-order are formed.

<Surface electrode>
The surface electrode 15 is formed on the amorphous oxide semiconductor layer 14 having a high Ga content (on the light receiving surface side). The material of the surface electrode 15 is not particularly limited as long as it is a conductive material, and is preferably made of, for example, Al or Ag. The surface electrode 15 is formed by, for example, resistance heating or electron beam vacuum deposition using Al metal or Ag metal, sputtering, MOCVD (Metal Organic Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy), or the like. It may be formed, or may be formed by applying (screen printing) a conductive paste containing aluminum powder or silver powder and then baking. For the patterning of the surface electrode 15, for example, an existing method such as an etching method using a photo process, a lift-off method, or a deposition method using a metal mask can be used.

  The surface electrode 15 may be an electrode formed by a vacuum deposition method or the like and laminated in the order of Ti / Pd / Ag.

The surface electrode 15 may be a transparent electrode made of ITO formed on the entire upper surface of the amorphous oxide semiconductor layer 14 having a high Ga content, and a group III element is used as a dopant in order to impart conductivity. An added conductive zinc oxide film may be used. As the dopant, any of B, Al, and Ga can be used. The surface electrode 15 having such a configuration is preferably formed by sputtering using In ₂ O ₃ —SnO ₂ or Al ₂ O ₃ —ZnO as a target.

  The surface electrode 15 may be an electrode in which a transparent electrode and a metal electrode are laminated. The surface electrode 15 may not be provided. In other words, the solar cell of the present invention may have a back electrode type structure (back contact structure) having no electrode on the light receiving surface. The surface electrode 15 may be provided on a transparent electrode made of ITO or the like.

  As described above, the solar cell 10 illustrated in FIG. 1 is illustrated as an example of the solar cell of the present invention. In the solar cell of the present invention, the amorphous oxide semiconductor layer 13 having a low Ga content is What is necessary is just to be provided in the p-type silicon layer 12 side rather than the high amorphous oxide semiconductor layer 14. Therefore, the amorphous oxide semiconductor layer 13 having a low Ga content is sandwiched by one or more layers (for example, an amorphous oxide semiconductor layer having a lower Ga content than the amorphous oxide semiconductor layer 13). It may be provided on the p-type silicon layer 12. The amorphous oxide semiconductor layer 14 having a high Ga content is one or more layers (for example, the Ga content is higher than the amorphous oxide semiconductor layer 13 and the Ga content is higher than the amorphous oxide semiconductor layer 14). May be provided on the amorphous oxide semiconductor layer 13 having a low Ga content. The surface electrode 15 is an amorphous oxide semiconductor layer having a high Ga content with one or more layers (for example, an amorphous oxide semiconductor layer having a Ga content higher than that of the amorphous oxide semiconductor layer 14) interposed therebetween. 14 may be provided. In addition to the amorphous oxide semiconductor layer 14 having a high Ga content, an amorphous oxide having an arbitrary Ga content is provided between the amorphous oxide semiconductor layer 13 having a low Ga content and the surface electrode 15. One or more physical semiconductor layers may be provided.

  The solar cell of the present invention is not limited to the configuration shown in FIG. For example, the solar cell of the present invention may include at least one of a cover glass, a protective film, an antireflection film, and a sealing film as necessary. The sealing film is preferably made of EVA (Ethylene-Vinyl Acetate, ethylene vinyl acetate) resin or epoxy resin.

Antireflection film is preferably made of _{SiO 2, TiO 2, SiN,} MgF 2 or Al ₂ O _3. The antireflection film made of SiO ₂ is preferably formed by a thermal oxidation method or the like. The antireflection film made of TiO ₂ or SiN is preferably formed by a chemical vapor deposition (CVD) method or the like. The antireflection film may have a single layer structure or a laminated structure. The location where the antireflection film is formed may be on the light receiving surface side, on the back surface side, or on both the light receiving surface side and the back surface side.

  In the solar cell 10 shown in FIG. 1, each material of the back surface electrode 11, the p-type silicon layer 12, and the surface electrode 15 is not limited to the said material. Moreover, in the solar cell 10 shown in FIG. 1, the amorphous oxide semiconductor layers 13 and 14 may contain materials other than the said material.

  The amorphous oxide semiconductor layers 13 and 14 in the present invention are applicable not only to single junction cells but also to multijunction solar cells. A single junction cell is a solar cell provided with one photoelectric conversion layer like the solar cell 10 shown in FIG. A multi-junction solar cell is a solar cell including two or more photoelectric conversion layers.

[Method for manufacturing solar cell]
An example of the manufacturing method of the solar cell 10 shown in FIG. 1 is shown below.

  A silicon wafer is prepared as the p-type silicon layer 12. After removing the surface damage layer of the silicon wafer, the amorphous oxide semiconductor layer 13 having a low Ga content, the amorphous oxide semiconductor layer 14 having a high Ga content, and a transparent electrode made of ITO are formed as a p-type silicon layer. 12 are sequentially formed. Thereafter, an Al paste is applied to the back side of the p-type silicon layer 12 by, for example, a screen printing method and then baked. Thereby, the back surface electrode 11 is formed. Note that the back electrode 11 may be formed before the amorphous oxide semiconductor layers 13 and 14 are formed. Further, an Ag paste is applied onto the amorphous oxide semiconductor layer 14 having a high Ga content by, for example, a screen printing method, and then fired. Thereby, the surface electrode 15 is formed. An annealing process (for example, 280 ° C.) may be performed on the solar cell thus obtained.

  Hereinafter, a method for forming the amorphous oxide semiconductor layers 13 and 14 will be described. The method for forming the amorphous oxide semiconductor layers 13 and 14 is not particularly limited as long as it is a method capable of forming an InGaZnO amorphous oxide semiconductor layer. For example, DC (Direct Current) sputtering or RF (Radio) Known thin film forming methods represented by sputtering methods such as frequency (sputtering) methods, chemical vapor deposition (CVD) methods, pulsed laser deposition (PLD) methods, molecular beam epitaxy (MBE) methods, and ion beam sputtering (IBS) methods Can be mentioned.

As a material source used in the thin film formation method, an oxide containing one or more of In, Ga and Zn may be used, or a metal body containing one or more of In, Ga and Zn may be used. Also good. As the oxide containing In, Ga, or Zn alone, In ₂ O ₃ , Ga ₂ O _3, ZnO, or the like can be used. As the oxide containing a plurality of types of In, Ga, and Zn, InGaZnO, InGaO, or the like can be used.

  Regardless of whether an oxide or a metal body is used as the material source, the amorphous oxide semiconductor layers 13 and 14 may be sequentially formed in a vacuum, a rare gas, or oxygen. Alternatively, the amorphous oxide semiconductor layers 13 and 14 may be formed sequentially while oxidizing the metal in a gas atmosphere containing oxygen.

  When forming the amorphous oxide semiconductor layer 13 having a low Ga content, a material source having a lower Ga content than the material source used when forming the amorphous oxide semiconductor layer 14 having a high Ga content is used. It is preferable to use it. Thereby, the Ga content in the amorphous oxide semiconductor layer 13 with a low Ga content can be made lower than the Ga content in the amorphous oxide semiconductor layer 14 with a high Ga content.

  Among the thin film forming methods, the amorphous oxide semiconductor layers 13 and 14 are preferably formed by sputtering. As a result, the amorphous oxide semiconductor layers 13 and 14 which are flat at the atomic level and have a thickness of nano order can be formed. Hereinafter, a specific method for forming the amorphous oxide semiconductor layers 13 and 14 will be described.

  As the sputtering target, a metal target containing In, Ga and Zn alone or in plural kinds, or a metal oxide target containing In, Ga and Zn alone or in plural kinds can be used. As the metal oxide target containing In or Ga and Zn alone or in plural kinds, the above oxides can be used. As a target for forming the amorphous oxide semiconductor layer 13 having a low Ga content, for example, InGaZnO (In: Ga: Zn = 1: 1: 1 (atomic ratio)) can be used. As a target for forming the amorphous oxide semiconductor layer 14 having a high Ga content, for example, InGaZnO (In: Ga: Zn = 1: 2: 1 (atomic ratio)), InGaZnO (In: Ga: Zn = 2: 2: 1 (atomic ratio)) or InGaZnO (In: Ga: Zn = 1: 3: 1 (atomic ratio)) or the like can be used.

  The p-type silicon layer 12 is fixed at a predetermined location in the sputtering apparatus, and a rare gas represented by Ar gas, oxygen gas, or both rare gas and oxygen gas are introduced into the sputtering apparatus.

  Next, the target material is knocked out by supplying DC power or RF power to the sputtering target. As a result, an amorphous oxide semiconductor layer 13 having a low Ga content and an amorphous oxide semiconductor layer 14 having a high Ga content are sequentially formed on the p-type silicon layer 12.

  At this time, the power supplied to the target depends on the type of the target and the like, but is preferably 50 W or more and 1000 W or less.

Moreover, you may form into a film, heating as needed.
For the formed amorphous oxide layer, in order to suppress oxygen vacancies, to increase the material uniformity in the thin film, or to increase the IV characteristics, a rare gas may be applied in vacuum as necessary. Heat treatment may be performed in an atmosphere containing oxygen gas or an atmosphere containing oxygen gas. The heat treatment may be performed in an atmosphere in which the amorphous oxide semiconductor layers 13 and 14 are formed, or may be performed in an atmosphere different from the atmosphere in which the amorphous oxide semiconductor layers 13 and 14 are formed. . For example, when the amorphous oxide semiconductor layers 13 and 14 are formed by introducing only a rare gas into the sputtering apparatus, the amorphous oxide semiconductor layers 13 and 14 are formed on the p-type silicon layer 12. It is preferable to perform the heat treatment in an atmosphere containing oxygen gas by introducing oxygen gas into the sputtering apparatus.

  In addition, each formation method of the back surface electrode 11, the p-type silicon layer 12, the amorphous oxide semiconductor layers 13 and 14, and the surface electrode 15 is not limited to the said method, The formation method in a liquid phase may be sufficient. Alternatively, a formation method in a gas phase may be used. Each forming method may be any method as long as it is a method suitable for forming each layer.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
In Example 1, a heterojunction solar cell having the configuration shown in FIG. 1 was manufactured. Specifically, an amorphous oxide semiconductor layer having a low Ga content (thickness 9 nm) and an amorphous oxide semiconductor layer having a high Ga content (thickness 18 nm) are formed on a cleaned silicon wafer. And a transparent electrode (thickness: 100 nm) made of ITO were sequentially formed. Next, a back electrode (aluminum) was formed on the back side of the silicon wafer, and a surface electrode (silver) was formed on the amorphous oxide semiconductor layer having a high Ga content. Thereafter, annealing was performed at 280 ° C.

An amorphous oxide semiconductor layer having a low Ga content and an amorphous oxide semiconductor layer having a high Ga content were formed by a DC magnetron sputtering method. InGaZnO (In: Ga: Zn = 1: 1: 1 (atomic ratio)) is used as a target of the amorphous oxide semiconductor layer having a low Ga content, and the amorphous oxide semiconductor layer having a high Ga content is used. As a target, InGaZnO (In: Ga: Zn = 1: 2: 1 (atomic ratio)) was used, and as a film forming gas, Ar and O ₂ were used. Elemental analysis in the depth direction of the formed amorphous oxide semiconductor layer was performed using secondary ion mass spectrometry. Confirmed that the Ga content of the amorphous oxide semiconductor layer provided on the p-type silicon layer side is lower than the Ga content of the amorphous oxide semiconductor layer provided far from the p-type silicon layer. did.

  When the heterojunction solar cell thus manufactured was irradiated with AM1.5G pseudo-sunlight and the cell characteristics were measured, the photoelectric conversion efficiency was 2.1%.

<Example 2>
A solar cell of Example 2 was manufactured in the same manner as in Example 1 except that an amorphous oxide semiconductor layer with a low Ga content having a thickness of 17 nm was formed.

  Specifically, an amorphous oxide semiconductor layer with a low Ga content (thickness: 17 nm) and an amorphous oxide semiconductor layer with a high Ga content (with a thickness of 18 nm) are formed on a cleaned silicon wafer. And a transparent electrode (thickness: 100 nm) made of ITO were sequentially formed. Next, a back electrode (aluminum) was formed on the back side of the silicon wafer, and a surface electrode (silver) was formed on the amorphous oxide semiconductor layer having a high Ga content. Thereafter, annealing was performed at 280 ° C.

An amorphous oxide semiconductor layer having a low Ga content and an amorphous oxide semiconductor layer having a high Ga content were formed by a DC magnetron sputtering method. InGaZnO (In: Ga: Zn = 1: 1: 1 (atomic ratio)) is used as a target of the amorphous oxide semiconductor layer having a low Ga content, and the amorphous oxide semiconductor layer having a high Ga content is used. As a target, InGaZnO (In: Ga: Zn = 1: 2: 1 (atomic ratio)) was used, and as a film forming gas, Ar and O ₂ were used. Elemental analysis in the depth direction of the formed amorphous oxide semiconductor layer was performed using secondary ion mass spectrometry. Confirmed that the Ga content of the amorphous oxide semiconductor layer provided on the p-type silicon layer side is lower than the Ga content of the amorphous oxide semiconductor layer provided far from the p-type silicon layer. did.

  When the heterojunction solar cell thus manufactured was irradiated with AM1.5G pseudo-sunlight and the cell characteristics were measured, the photoelectric conversion efficiency was 1.8%.

<Comparative Example 1>
A heterojunction solar cell of Comparative Example 1 was manufactured in the same manner as in Example 1 except that the solar cell was manufactured without forming an InGaZnO layer having a low Ga content.

  Specifically, an amorphous oxide semiconductor layer having a high Ga content (thickness: 18 nm) and a transparent electrode (thickness: 100 nm) made of ITO were formed on a cleaned silicon wafer. Next, a back electrode (aluminum) was formed on the back side of the silicon wafer, and a surface electrode (silver) was formed on the amorphous oxide semiconductor layer having a high Ga content. Thereafter, annealing was performed at 280 ° C.

An amorphous oxide semiconductor layer having a high Ga content was formed by a DC magnetron sputtering method. InGaZnO (In: Ga: Zn = 1: 2: 1 (atomic ratio)) was used as the target, and Ar and O ₂ were used as the film forming gas.

  When the heterojunction solar cell manufactured as described above was irradiated with AM1.5G pseudo-sunlight and measured for cell characteristics, the photoelectric conversion efficiency was 1.3%.

<Discussion>
The photoelectric conversion efficiency of the solar cells of Examples 1 and 2 was higher than the photoelectric conversion efficiency of the solar cell of Comparative Example 1. The following can be considered as the reason. In the solar cells of Examples 1 and 2, since the amorphous oxide semiconductor layer having a low Ga content is provided between the silicon wafer and the amorphous oxide semiconductor layer having a high Ga content, the heterointerface Carrier recombination in is suppressed. On the other hand, in the solar cell of Comparative Example 1, since the amorphous oxide semiconductor layer having a low Ga content is not provided between the silicon wafer and the amorphous oxide semiconductor layer having a high Ga content, the heterointerface The carrier recombination in was not suppressed, and thus the photoelectric conversion efficiency was lowered.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10 solar cell, 11 back electrode, 12 p-type silicon layer, amorphous oxide semiconductor layer with low 13 Ga content, amorphous oxide semiconductor layer with high 14 Ga content, 15 surface electrode.

Claims (3)

a p-type silicon layer;
A solar cell provided on the p-type silicon layer, comprising two or more amorphous oxide semiconductor layers containing In, Ga, and Zn and having different Ga contents;
The Ga content in the amorphous oxide semiconductor layer provided on the p-type silicon layer side is lower than the Ga content in the amorphous oxide semiconductor layer provided at a position far from the p-type silicon layer. battery.   2. The solar cell according to claim 1, wherein the p-type silicon layer includes at least one of a single crystal p-type silicon layer, a polycrystalline p-type silicon layer, and an amorphous p-type silicon layer.   The solar cell according to claim 1 or 2, wherein a thickness of the amorphous oxide semiconductor layer provided on the p-type silicon layer side is 10 nm or less.

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