JP2015198211A - photoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sulfuration resistance of a lower electrode in a photoelectric element including a light-absorbing layer made of a sulfide-based compound semiconductor.SOLUTION: A photoelectric element includes: a substrate made of alkali glass; a lower electrode formed on a surface of the substrate; and a light-absorbing layer formed on a surface of the lower electrode and made of a sulfide-based compound semiconductor. The lower electrode includes: a first electrode layer formed on the substrate side and made of a metal material containing one or more elements selected from the group consisting of Mo, Ti, Zr, Hf, Ta, Nb and W; and a second electrode layer formed on the light-absorbing layer side and made of crystalline ZrB.

Description

  The present invention relates to a photoelectric element, and more particularly to a photoelectric element that can suppress an increase in electrical resistance due to sulfurization of a lower electrode.

  A photoelectric element refers to an element that can convert photon energy into an electrical signal (photoelectric conversion) through some physical phenomenon. A solar cell is a kind of photoelectric element, and can efficiently convert light energy of sunlight into electric energy.

The semiconductor used in solar cells, monocrystalline Si, polycrystalline Si, amorphous Si, GaAs, InP, CdTe, CuIn 1-x Ga x Se 2 (CIGS), Cu 2 ZnSnS 4 (CZTS) such as is known Yes.
Among these, chalcogenite-based compounds represented by CIGS and CZTS have a large light absorption coefficient, so that a thin film advantageous for cost reduction is possible. In particular, a solar cell using CIGS as a light absorption layer has high conversion efficiency in a thin film solar cell, and conversion efficiency exceeding that of a solar cell using polycrystalline Si is also obtained. However, CIGS has a problem that it contains an environmental load element and a rare element.
On the other hand, CZTS has a band gap energy (1.4 to 1.5 eV) suitable for a solar cell and is characterized by not containing an environmental load element or a rare element.

In a thin film solar cell using a compound semiconductor, Mo is usually used for the lower electrode. Mo has a low electrical specific resistance, is relatively inexpensive, and has a high resistance to sulfidation. Therefore, Mo is particularly suitable as a lower electrode material of a thin film solar cell using a sulfide compound semiconductor.
However, even Mo with high sulfidation resistance is formed with Mo-S having high electrical resistance on its surface when exposed to a sulfidation atmosphere. As a result, in the case of manufacturing a light absorption layer made of a sulfide-based compound semiconductor by using a method of sulfiding a precursor, if the sulfidation condition becomes severe, it causes a decrease in solar cell characteristics.

In order to solve this problem, various proposals have heretofore been made.
For example, Patent Document 1 discloses an electrode material containing at least Si and containing 70 at% or more of Mo.
In this document, when Mo-Si is used as the lower electrode, Si in the material is selectively sulfided or selenized on the electrode surface during sulfidation or selenization, and Mo sulfidation or selenization is suppressed. Points are listed.

Patent Document 2 discloses a sulfide-resistant electrode material made of a Mo—Al alloy or a Mo—Ga alloy.
In the same document,
(1) The point that Al or Ga on the surface of the material is selectively sulfided during sulfidation, the produced sulfide functions as a protective film, and sulfidation inside the electrode is suppressed, and
(2) Since Al and Ga are both metal elements, it is described that the increase in electrical resistance is small even when alloyed with Mo.

As described in Patent Documents 1 and 2, when a certain element is added to Mo, the sulfidation resistance of Mo is improved. However, when a Mo—Si alloy is used as the lower electrode, the adhesion with the light absorption layer may be reduced.
On the other hand, when Mo—Al alloy or Mo—Ga alloy is used as the lower electrode, the sulfidation resistance of Mo is improved without lowering the adhesion. However, in order to improve the solar cell characteristics, it is desired to further improve the sulfidation resistance of the lower electrode.

JP 2011-018464 A JP 2013-112851 A

The problem to be solved by the present invention is to improve the sulfidation resistance of the lower electrode in a photoelectric device having a light absorption layer made of a sulfide compound semiconductor.
Another problem to be solved by the present invention is to suppress a decrease in conversion efficiency due to sulfidation of the lower electrode in a photoelectric device including a light absorption layer made of a sulfide-based compound semiconductor.

In order to solve the above-described problems, the gist of the photoelectric device according to the present invention is as follows.
(1) The photoelectric element is
A substrate made of alkali glass;
A lower electrode formed on the surface of the substrate;
A light absorption layer made of a sulfide compound semiconductor formed on the surface of the lower electrode.
(2) The lower electrode is
A first electrode layer formed on the substrate side and made of a metal material containing at least one element selected from the group consisting of Mo, Ti, Zr, Hf, Ta, Nb, and W;
A second electrode layer made of crystalline ZrB ₂ formed on the light absorption layer side;
It has.

  Ti, Zr, Hf, Ta, Nb, Mo, and W have higher sulfidation resistance than other metal materials. However, even with such a sulfidation-resistant metal material, when exposed to a sulfidation atmosphere, a sulfide with high electrical resistance is formed on the surface. Therefore, when such a sulfidation-resistant metal material is used as it is as the lower electrode of the photoelectric element, the conversion efficiency decreases due to the sulfidation of the lower electrode.

In contrast, in the photoelectric device having a laminated structure of the substrate / lower electrode / light absorption layer, a first electrode layer made of the lower electrode from the sulfidation resistance metal material, 2 of the second electrode layer made of crystalline ZrB ₂ With a layer structure, it is possible to suppress a decrease in conversion efficiency due to the sulfidation of the first electrode layer. This is presumably because crystalline ZrB ₂ suppresses sulfidation of the first electrode layer, thereby suppressing an increase in the DC resistance component of the photoelectric element.

_{2 is} an XRD spectrum of a ZrB ₂ thin film formed at 400 ° C. (FIG. 1A) or room temperature (FIG. 1B). Is a graph showing the relationship between the thickness and the conversion efficiency of the ZrB ₂ layers.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Photoelectric element]
The photoelectric element according to the present invention has the following configuration.
(1) The photoelectric element is
A substrate made of alkali glass;
A lower electrode formed on the surface of the substrate;
A light absorption layer made of a sulfide compound semiconductor formed on the surface of the lower electrode.
(2) The lower electrode is
A first electrode layer formed on the substrate side and made of a metal material containing at least one element selected from the group consisting of Mo, Ti, Zr, Hf, Ta, Nb, and W;
A second electrode layer made of crystalline ZrB ₂ formed on the light absorption layer side;
It has.

[1.1. substrate]
In the present invention, a substrate made of alkali glass is used as the substrate.
Alkaline glass
(1) is relatively inexpensive,
(2) High adhesion to sulfide-resistant metal materials,
(3) The alkali component contained in the glass promotes the grain growth of the sulfide compound semiconductor.
There are advantages such as. Therefore, alkali glass is suitable as a substrate material.

[1.2. Lower electrode]
The lower electrode is formed on the surface of the substrate. In the present invention, the lower electrode has a two-layer structure of a first electrode layer made of a metal material containing a sulfide-resistant metal element and a second electrode layer made of crystalline ZrB ₂ . This is different from the conventional one. The first electrode layer is formed on the substrate side. The second electrode layer is formed on the light absorption layer side.

[1.2.1. First electrode layer]
The first electrode layer is made of a metal material containing a sulfide-resistant metal element.
In the present invention, the “sulfur resistant metal element” means any one or more elements selected from the group consisting of Mo, Ti, Zr, Hf, Ta, Nb, and W. All of these elements are less likely to form sulfides with higher electrical resistance than other elements.

  The first electrode layer is preferably made of only a sulfide-resistant metal element, but may contain other metal elements. However, the smaller the content of the metal element that lowers the sulfide resistance of the first electrode layer and the adhesion to the substrate, the better. In order to suppress a decrease in conversion efficiency, the content of the sulfide-resistant metal element contained in the first electrode layer is preferably 80 wt% or more, and more preferably 90 wt% or more.

The ratio of each sulfide-resistant metal element contained in the first electrode layer is not particularly limited and can be arbitrarily selected according to the purpose.
Among sulfide-resistant metal elements, Mo has a low electrical resistivity, is relatively inexpensive, and has a high resistance to sulfide. Therefore, Mo is suitable as a material for the first electrode layer.
In order to produce a photoelectric device with high conversion efficiency at low cost, the content of Mo contained in the first electrode layer is preferably 80 wt% or more, and more preferably 90 wt%. The first electrode layer is preferably made of Mo (that is, made of Mo and inevitable impurities).

  The thickness of the first electrode layer is not particularly limited, and an optimum thickness can be selected according to the purpose. In general, if the thickness of the first electrode layer becomes too thin, the resistance of the first electrode layer increases due to sulfidation, or the first electrode layer tends to peel off. On the other hand, there is no practical benefit even if the first electrode layer is made thicker than necessary. The thickness of the first electrode layer is usually about 200 to 1000 nm.

[1.2.2. Second electrode layer]
The second electrode layer, a crystalline ZrB _2.
In the present invention, “crystalline ZrB ₂ ” refers to a solid having a periodic atomic arrangement in which a diffraction phenomenon occurs when an X-ray or electron beam is incident. More specifically, in the θ-2θ spectrum obtained by powder XRD measurement,
(A) the half width of the 001 peak is 2 ° or less, and
(B) The intensity of the 001 peak is more than twice the intensity of the amorphous halo pattern.

The ZrB ₂ thin film may be amorphous depending on the manufacturing method. However, even if an amorphous ZrB ₂ thin film is used as the second electrode layer, high characteristics cannot be obtained. This is presumably because B in ZrB ₂ diffuses into the light absorption layer and reacts with the light absorption layer.
On the other hand, when crystalline ZrB ₂ is used as the second electrode layer, diffusion of B into the light absorption layer is suppressed. At the same time, the crystalline ZrB ₂ can suppress the sulfidation of the first electrode layer.

The thickness of the second electrode layer affects the conversion efficiency of the photoelectric element. If the second electrode layer becomes too thin, it becomes difficult to suppress sulfidation of the first electrode layer. Therefore, the thickness of the second electrode layer is preferably 5 nm or more. The thickness of the second electrode layer is more preferably 7 nm or more, and further preferably 9 nm or more.
On the other hand, the alkali component contained in the substrate diffuses to the light absorption layer when the light absorption layer is formed. The alkali component diffused into the light absorption layer has an action of growing the crystal grains of the sulfide compound semiconductor. If the thickness of the second electrode layer becomes too thick, the diffusion of the alkali component into the light absorption layer is inhibited, and the grain growth of the sulfide-based compound semiconductor becomes insufficient. Therefore, the thickness of the second electrode layer is preferably 100 nm or less. The thickness of the second electrode layer is more preferably 50 nm or less, further preferably 30 nm or less, more preferably 25 nm or less, and still more preferably 20 nm or less.

Such a second electrode layer made of crystalline ZrB _{2 can} be produced, for example, by sputtering a ZrB ₂ thin film on the surface of the substrate while the substrate is heated to a predetermined temperature. Details of the method for producing the crystalline ZrB ₂ thin film will be described later.

[1.3. Light absorption layer]
The light absorption layer is formed on the surface of the lower electrode (that is, the surface of the second electrode layer). In the present invention, the light absorption layer is made of a sulfide compound semiconductor.
The composition of the sulfide compound semiconductor is not particularly limited, and various compositions can be selected according to the purpose.

Examples of sulfide compound semiconductors include:
(A) Cu ₂ ZnSnS ₄ (CZTS) based compound semiconductor,
(B) Cu ₂ SnS ₃ (CTS) compound semiconductor,
(C) CuInS ₂ (CIS) compound semiconductor,
and so on.
Among these, the CZTS-based compound semiconductor has a relatively high conversion efficiency and does not contain a rare element or an environmental load element, and thus is suitable as a material for the light absorption layer.

Here, the “CZTS compound semiconductor” refers to a semiconductor based on Cu ₂ ZnSnS ₄ (CZTS).
In the present invention, “CZTS compound semiconductor” includes not only stoichiometric compounds but also all non-stoichiometric compounds, or all compounds containing Cu, Zn, Sn, and S as a main component. It is.
The CZTS-based compound semiconductor may be composed only of Cu, Zn, Sn, and S, or may further include other chalcogen elements, various dopants, unavoidable impurities, and the like in addition to these.

  It is known that the characteristics of CZTS-based compound semiconductors depend on element ratios (that is, Cu / Zn ratio, Cu / Sn ratio, and (Cu + Zn + Sn) / S ratio). When a CZTS compound semiconductor is used as the light absorption layer, the element ratio is not particularly limited, and an optimum element ratio can be selected according to the purpose.

  The thickness of the light absorption layer is not particularly limited, and an optimum thickness can be selected according to the composition of the light absorption layer. Usually, the thickness of the light absorption layer is about 500 nm to 2000 nm.

[1.4. Other components]
The photoelectric element may further include components other than the substrate, the lower electrode, and the light absorption layer described above. In the case of a photoelectric element using a sulfide-based compound semiconductor as the light absorption layer, it usually further includes a buffer layer, a transparent electrode layer, and a surface electrode.

[1.4.1. Buffer layer]
The buffer layer is formed on the surface of the light absorption layer. In the present invention, the composition of the buffer layer is not particularly limited, and various compositions can be selected according to the purpose. Examples of the material for the buffer layer include CdS, (Cd, Zn) S, and (Zn, Mg) O.
The thickness of the buffer layer is not particularly limited, and an optimum thickness can be selected according to the purpose. The thickness of the buffer layer is usually 10 nm to 150 nm.

[1.4.2. Transparent electrode layer]
The transparent electrode layer is formed on the surface of the buffer layer. In the present invention, the composition of the transparent electrode layer is not particularly limited, and various compositions can be selected according to the purpose. Examples of the material for the transparent electrode layer include ZnO: Al, ZnO: Ga (GZO), ZnO: B, In—Sn—O, In—Zn—O, SnO ₂ : Sb, and TiO ₂ : Nb.
The thickness of the transparent electrode layer is not particularly limited, and an optimum thickness can be selected according to the purpose. The thickness of the transparent electrode layer is usually 100 nm to 1000 nm.

[1.4.3. Surface electrode]
The surface electrode is formed on the surface of the transparent electrode layer. The material of the surface electrode is not particularly limited, and various materials can be used.
Examples of the material for the surface electrode include Al, Cu, Ag, Au, and alloys containing any one or more of these. Specific examples of such an alloy include an Al—Ti alloy, an Al—Mg alloy, an Al—Ni alloy, a Cu—Ti alloy, a Cu—Sn alloy, a Cu—Zn alloy, a Cu—Au alloy, and Ag. -Ti alloy, Ag-Sn alloy, Ag-Zn alloy, Ag-Au alloy, and the like.

[1.4.4. Additional layers]
The photoelectric element according to the present invention may further include an additional layer in addition to the above-described layers.
Specifically, as an additional layer,
(1) an adhesive layer for increasing the adhesion between the substrate and the lower electrode;
(2) a light scattering layer for reflecting incident light and increasing light absorption efficiency in the light absorption layer, which is formed on the surface electrode side of the light absorption layer;
(3) a light scattering layer provided on the substrate side of the light absorption layer;
(4) an antireflection layer for reducing the amount of incident light reflected by the transparent electrode layer and increasing the light absorption efficiency of the light absorption layer;
and so on.
In the present invention, the material of the additional layer is not particularly limited, and various materials can be used depending on the purpose.

[2. Photoelectric element manufacturing method]
The photoelectric device according to the present invention can be manufactured by laminating thin films having a predetermined composition and thickness on a substrate surface in a predetermined order.

[2.1. First electrode layer forming step]
In the present invention, the lower electrode has a two-layer structure of a first electrode layer and a second electrode layer. Therefore, first, a first electrode layer is formed on the surface of the substrate (first electrode layer forming step). The method for forming the first electrode layer is not particularly limited, and various methods can be used.
Examples of the method for forming the first electrode layer include sputtering, vacuum deposition, pulsed laser deposition (PLD), plating, chemical solution deposition (CBD), electrophoretic deposition (EPD), and chemical vapor. There are a film formation (CVD) method, a spray pyrolysis film formation (SPD) method, a screen printing method, a spin coating method, a fine particle deposition method, and the like.

[2.2. Second electrode layer forming step]
Next, a second electrode layer is formed on the surface of the first electrode layer (second electrode layer forming step). In the present invention, the second electrode layer is made of crystalline ZrB ₂ . Therefore, the method for forming the second electrode layer needs to be a method capable of forming a crystalline ZrB ₂ thin film.

As a method for forming the second electrode layer, for example,
(A) Substrate temperature: a method of sputtering using a ZrB ₂ target under conditions of 300 ° C. or more and 500 ° C. or less (high temperature sputtering method),
(B) Substrate temperature: PLD method using a ZrB ₂ target under conditions of 300 ° C. or more and 500 ° C. or less,
(C) Substrate temperature: a reactive sputtering method in which a ZrB ₂ target is sputtered in BH ₃ gas under conditions of 300 ° C. or more and 500 ° C. or less,
and so on.
Among these, the high-temperature sputtering method is suitable as a method for forming the second electrode layer because the crystalline ZrB ₂ thin film can be formed relatively easily.

[2.3. Light absorption layer forming step]
Next, a light absorption layer made of a sulfide compound semiconductor is formed on the surface of the second electrode (light absorption layer forming step).
The light absorbing layer made of a sulfide compound semiconductor is usually
(A) forming a precursor film (for example, a metal film, a sulfide film, an oxide film, etc.) containing a metal element constituting the sulfide-based compound semiconductor on the substrate surface;
(B) It can be produced by sulfiding the precursor film.

  The method for forming the precursor film is not particularly limited, and various methods can be used depending on the purpose. The details of the method of forming the precursor film are the same as the method of forming the lower electrode, and thus the description thereof is omitted.

The sulfidation of the precursor film is performed by heating the precursor film at a predetermined temperature in a sulfur atmosphere (for example, a sulfur vapor atmosphere, an N ₂ + 20% H ₂ S atmosphere, etc.).
It is preferable to select an optimum heating temperature according to the composition of the precursor film. For example, when a CZTS compound semiconductor is produced, the sulfiding temperature is preferably 500 ° C. to 600 ° C.

[2.4. Other layer formation process]
After forming the light absorption layer, other layers (for example, a buffer layer, a transparent electrode layer, a surface electrode, etc.) are formed as necessary. When an additional layer is formed between the layers, the additional layer is formed before the next layer is formed.
The formation method of another layer is not specifically limited, A various method can be used according to the objective. The details of the method of forming other layers are the same as the method of forming the lower electrode, and thus the description thereof is omitted.

[3. Action]
As a lower electrode of a CZTS solar cell, Mo which is relatively inexpensive and has sulfur resistance is widely used. However, Mo-S having high electrical resistance is formed on the Mo surface during the sulfidation process, and the solar cell characteristics are deteriorated.
On the other hand, ZrB ₂ has higher sulfidation resistance than Mo. However, when ZrB _{2 is formed} by a normal sputtering method, it becomes amorphous. Amorphous ZrB ₂ easily reacts with CZTS, and thus causes a reduction in the conversion efficiency of the solar cell.

On the other hand, when ZrB ₂ is formed by sputtering or the like, a crystalline ZrB ₂ thin film can be obtained if the substrate temperature during film formation is 300 to 500 ° C. When this crystalline ZrB ₂ thin film is formed on the surface of the Mo film, the formation of Mo—S having high electrical resistance is suppressed, and at the same time, the reaction between the ZrB ₂ thin film and CZTS is suppressed. As a result, the solar cell characteristics are improved.

Amorphous ZrB ₂ itself has high sulfidation resistance. However, it is considered that when amorphous ZrB ₂ is adjacent to an inorganic compound or an intermetallic compound, the bond of Zr—B is not strong, so that B easily diffuses into the inorganic compound or the intermetallic compound.
On the other hand, crystalline ZrB ₂ not only has high sulfidation resistance, but also does not react with other compounds because it has a strong bond / crystal structure. As a result, it is estimated that the above effects were obtained.

Crystalline ZrB ₂ has an appropriate thickness. This is presumed to be the influence of alkali diffusion from the glass substrate. That is, it is known that the characteristics of CZTS solar cells are improved by the effect of alkali diffused from the glass substrate. Since the Mo film has a columnar structure, alkali is relatively easily diffused. On the other hand, since ZrB ₂ has a fine microstructure, alkali hardly diffuses. Therefore, when ZrB ₂ is excessively thick, it is considered that ZrB ₂ suppresses alkali diffusion and the characteristics of the solar cell are deteriorated.

  The same applies to a photoelectric device using a sulfide compound semiconductor other than CZTS, and a case where a sulfide-resistant metal element other than Mo is used as the first electrode layer, and the first electrode layer, the light absorption layer, When the second electrode layer is interposed between the two, the sulfidation of the first electrode layer is suppressed, and the characteristic deterioration caused by the reaction between the second electrode layer and the light absorption layer can be suppressed.

(Examples 1-3, Comparative Examples 1-3)
[1. Preparation of sample]
[1.1. Preparation of crystal structure evaluation sample]
By RF sputtering, using a ZrB ₂ target and an alkali glass substrate (hereinafter, simply referred to as "glass substrate") was deposited ZrB ₂ on. The sputtering conditions are as follows.
Film thickness: 100nm
Substrate temperature during film formation: room temperature (Comparative Examples 2-3) or 400 ° C. (Examples 1-3)
Base pressure: 10 ^-5 to 10 ^-6 Pa
Film formation conditions: Ar 20 sccm, 1.2 × 10 ⁻¹ Pa
RF power output: 200W

[1.2. Fabrication of solar cell]
First, ZrB ₂ having a different film thickness and film formation temperature was formed on the surface of the Mo / glass substrate. The film thickness of ZrB ₂ was 10 nm, 100 nm, 200 nm, or 800 nm. The film formation temperature was room temperature (Comparative Examples 2-3) or 400 ° C. (Examples 1-3).
Next, a Cu / Zn / ZnS laminated precursor is formed on the surface of the ZrB ₂ / Mo / glass substrate, and is subjected to sulfidation treatment at 580 ° C. for 20 minutes in an N ₂ + 20% H ₂ S atmosphere. Formed.
Subsequently, a CdS buffer layer, a transparent electrode layer, and a surface electrode layer were formed to obtain a solar cell.

[2. Test method]
[2.1. XRD measurement]
XRD measurement was performed using the sample for crystal structure evaluation.
[2.2. Solar cell characteristics]
The solar cell characteristics were evaluated under the conditions of 1 sun and AM1.5.

[3. result]
[3.1. Crystal structure]
FIG. 1 shows an XRD spectrum of a sample formed on a glass substrate. In the sample heated at 400 ° C. (FIG. 1A), a sharp peak corresponding to ZrB ₂ was observed near 2θ = 25 °, and a peak corresponding to ZrB ₂ was also observed near 52 °. FIG. 1A shows that a ZrB ₂ thin film having good crystallinity was formed under the sputtering conditions.
On the other hand, in the sample formed at room temperature (FIG. 1B), no clear peak was observed, and an amorphous film was formed.

[3.2. Solar cell characteristics]
Table 1 shows the characteristics of solar cells manufactured by changing the film formation conditions of the ZrB ₂ film. FIG. 2 shows the relationship between the thickness of the ZrB ₂ layer and the conversion efficiency. From Table 1 and FIG. 2, the following can be understood.

(1) The solar cell provided with the ZrB ₂ film formed at room temperature (Comparative Examples 2 and 3) was greatly deteriorated in solar cell characteristics as compared with the solar cell without the ZrB ₂ film (Comparative Example 1). From the depth analysis of the film, it was found that B was diffused from ZrB ₂ to CZTS.
(2) The solar cell (Example 1) provided with a 10 nm thick ZrB ₂ film formed at 400 ° C. was found to have improved characteristics as compared with Comparative Example 1.
(3) Even when the ZrB ₂ film was formed at 400 ° C., when the film thickness of the ZrB ₂ film increased (Examples 2 and 3), the IV characteristics deteriorated. That is, it has been found that crystalline ZrB ₂ having a thickness of about 10 nm is effective in improving the solar cell performance, but conversely reduces the performance when it is too thick. Moreover, in order to obtain a conversion efficiency equal to or higher than that of Comparative Example 1, it was found that the thickness of the ZrB ₂ film is preferably 30 nm or less.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  The photoelectric element according to the present invention can be used for thin film solar cells, photoconductive cells, photodiodes, phototransistors, sensitized solar cells and the like.

Claims (4)

A photoelectric device having the following configuration.
(1) The photoelectric element is
A substrate made of alkali glass;
A lower electrode formed on the surface of the substrate;
A light absorption layer made of a sulfide compound semiconductor formed on the surface of the lower electrode.
(2) The lower electrode is
A first electrode layer formed on the substrate side and made of a metal material containing at least one element selected from the group consisting of Mo, Ti, Zr, Hf, Ta, Nb, and W;
A second electrode layer made of crystalline ZrB ₂ formed on the light absorption layer side;
It has.   The photoelectric device according to claim 1, wherein the second electrode layer has a thickness of 5 nm to 100 nm.   The photoelectric device according to claim 1, wherein the first electrode layer is made of Mo. 4. The first electrode layer according to claim 1, wherein the second electrode layer is formed by sputtering using a ZrB ₂ target under a substrate temperature of 300 ° C. to 500 ° C. 4. The photoelectric device described in 1.

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