阅读说明：本技术 制造多层薄膜的工艺、制造太阳能电池的方法、和制造太阳能电池组件的方法 (Process for manufacturing multilayer thin film, method for manufacturing solar cell, and method for manufacturing solar cell module ) 是由 保西祐弥 芝崎聪一郎 中川直之 山崎六月 平冈佳子 山本和重 于 2020-08-25 设计创作，主要内容包括：本发明提供制造多层薄膜的工艺、以及制造太阳能电池的方法、制造多结太阳能电池的方法、制造太阳能电池组件的方法。所述制造多层薄膜的工艺包括：在第一透明电极上形成包含Cu-(2)O作为主要成分的光电转换层；和将具有形成在所述第一透明电极上的所述光电转换层的构件在氧浓度为5.0×10～(-8)[g/L]至5.0×10～(-5)[g/L]的第一气氛下放置1h至1600h。(The invention provides a process for manufacturing a multilayer thin film, and a method for manufacturing a solar cell, a method for manufacturing a multijunction solar cell, and a method for manufacturing a solar cell module. The process for manufacturing a multilayer thin film includes: forming a first transparent electrode containing Cu 2 A photoelectric conversion layer containing O as a main component; and a member having the photoelectric conversion layer formed on the first transparent electrode is formed at an oxygen concentration of 5.0 × 10 ‑8 [g/L]To 5.0X 10 ‑5 [g/L]Is placed under the first atmosphere for 1h to 1600 h.)

1. A process for manufacturing a multilayer thin film, comprising:

forming a first transparent electrode containing Cu₂A photoelectric conversion layer containing O as a main component; and

a member having the photoelectric conversion layer formed on the first transparent electrode is formed at an oxygen concentration of 5.0 × 10^-8[g/L]To 5.0X 10^-5[g/L]Is placed under the first atmosphere for 1h to 1600 h.

2. The process for producing a multilayer thin film according to claim 1, wherein the concentration of water vapor in the first atmosphere during the standing under the first atmosphere is 5.0×10^-8[g/L]To 5.0X 10^-5[g/L]。

3. The process for producing a multilayer thin film according to claim 1 or 2, further comprising the steps of: the member having the photoelectric conversion layer formed on the first transparent electrode is left under a second air atmosphere of 0 ℃ to 50 ℃ for 1h or less before being left under the first atmosphere.

4. The process for producing a multilayer thin film according to any one of claims 1 to 3, wherein the temperature of the first atmosphere during the placing under the first atmosphere is 0 ℃ to 100 ℃.

5. The process for producing a multilayer thin film according to any one of claims 1 to 4, wherein a holding time in the first atmosphere during the placing under the first atmosphere is 72h to 1600 h.

6. The process for producing a multilayer thin film according to any one of claims 1 to 5, wherein the oxygen concentration in a low-oxygen atmosphere during the standing under the first atmosphere is 5.0 x 10^-8[g/L]To 3.5X 10^-5[g/L]And is and

the water vapor concentration in the low-oxygen atmosphere during the standing under the first atmosphere is 5.0 × 10^-8[g/L]To 4.0X 10^-5[g/L]。

7. The process for producing a multilayer thin film according to any one of claims 1 to 6, wherein a holding time in the first atmosphere during the placing under the first atmosphere is defined as t [ h ]]The oxygen concentration in the first atmosphere is defined as C_O[g/L]And the concentration of water vapor in the first atmosphere is defined as C_W[g/L]When the temperature of the water is higher than the set temperature,

satisfies the condition of 1.0 x 10^-7[h·g/L]≤t×C_O[h·g/L]≤1.6×10^-3[h·g/L]And is and

satisfies the condition of 1.0 x 10^-7[h·g/L]≤t×C_W[h·g/L]≤6.5×10^-2[h·g/L]。

8. A method of manufacturing a solar cell, comprising manufacturing a multilayer thin film by the process for manufacturing a multilayer thin film according to any one of claims 1 to 7.

9. A method of manufacturing a multijunction solar cell, comprising manufacturing a multilayer thin film with the process of manufacturing a multilayer thin film of any one of claims 1 to 7.

10. A method of manufacturing a solar cell module, comprising manufacturing a multilayer thin film by the process for manufacturing a multilayer thin film according to any one of claims 1 to 7.

Technical Field

Embodiments described herein relate generally to a process for manufacturing a multilayer thin film, a method for manufacturing a solar cell, and a method for manufacturing a solar cell module.

Background

Examples of high efficiency solar cells include multi-junction (series) solar cells. Tandem solar cells may utilize cells with high spectral sensitivity for each band, and thus have higher efficiency than single junction solar cells. The cuprous oxide compound is an inexpensive material and has a wide band gap, and is expected to be a top cell of a tandem solar cell. Meanwhile, although the efficiency of the previous cuprous oxide solar cell produced by oxidizing copper foil is said to be about 8%, the efficiency is lower than the theoretical maximum efficiency. This is probably because when the copper foil is oxidized and a heterogeneous phase such as copper oxide on the top surface is removed by etching, it is impossible to completely remove the phase and constituent elements in the etching solution remain. Therefore, a good p-n junction cannot be formed. Furthermore, it is necessary to oxidize a foil having a thickness of about 0.1mm and then polish it to about 20 μm in this process. Therefore, it is difficult to make the area large.

As a process for producing a cuprous oxide thin film, a sputtering method is known. In some reports, this process has been used to make cuprous oxide films. However, the conversion efficiency is yet to be further improved.

Documents of the prior art

Non-patent document

Non-patent document 1 Sangg Woon Lee, Yun Seog Lee et al, adv. energy Mater, 2014,4,1301916

Disclosure of Invention

Problems to be solved by the invention

Embodiments described herein provide processes for fabricating high quality multilayer thin films, methods for fabricating solar cells, methods for fabricating multijunction solar cells, and methods for fabricating solar cell modules.

Means for solving the problems

The process of manufacturing a multilayer thin film of an embodiment includes: forming a first transparent electrode containing Cu₂A photoelectric conversion layer containing O as a main component; and a member having the photoelectric conversion layer formed on the first transparent electrode is formed at an oxygen concentration of 5.0 × 10^-8[g/L]To 5.0X 10^-5[g/L]Is placed under the first atmosphere for 1h to 1600 h.

Drawings

Fig. 1 is a schematic cross-sectional view of a multilayer thin film in an embodiment.

Fig. 2 is a flowchart illustrating a process of manufacturing a multilayer thin film according to an embodiment.

Fig. 3 is a schematic cross-sectional view of a multilayer thin film in an embodiment.

Fig. 4 is a schematic cross-sectional view of a solar cell in an embodiment.

Fig. 5 is a schematic cross-sectional view of a multijunction solar cell in an embodiment.

Fig. 6 is a schematic view of a solar cell module in an embodiment.

Fig. 7 is a schematic cross-sectional view of a solar cell module in an embodiment.

Fig. 8 is a schematic diagram of a photovoltaic power generation system in an embodiment.

Fig. 9 is a schematic diagram of a vehicle in the embodiment.

Fig. 10 is a table of the embodiment.

FIG. 11 is a table of examples, reference examples and comparative examples.

FIG. 12 is a table of examples, reference examples and comparative examples.

Detailed Description

(first embodiment)

The first embodiment pertains to a multilayer thin film and a process for manufacturing the same. Fig. 1 is a schematic cross-sectional view illustrating a multilayer film 100. The multilayer film 100 shown in fig. 1 includes: a first transparent electrode 1; and a photoelectric conversion layer 2 formed on the first transparent electrode 1. The surface of the photoelectric conversion layer 2 opposite to the first transparent electrode 1 side has a CuO-containing region 20. Unless otherwise stated herein, values at 25 ℃ and 1atm are indicated.

The first transparent electrode 1 is a layer stacked on the photoelectric conversion layer 2. In fig. 1, a first transparent electrode 1 is in direct contact with a photoelectric conversion layer 2. The main surface of the first transparent electrode 1 faces the main surface of the photoelectric conversion layer 2, and has an interface. The entire surface of the photoelectric conversion layer 2 facing the first transparent electrode 1 is preferably in direct contact with the first transparent electrode 1. The first transparent electrode 1 is a p-type electrode in direct contact with the p-type photoelectric conversion layer 2. The first transparent electrode 1 has a thickness of, for example, preferably 100nm to 1000 nm.

The first transparent electrode 1 preferably includes a transparent conductive oxide film. Examples of the transparent conductive oxide film include, but are not limited to, Indium Tin Oxide (ITO), aluminum-doped zinc oxide (AZO), boron-doped zinc oxide (BZO), gallium-doped zinc oxide (GZO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), titanium-doped indium oxide (ITiO), Indium Zinc Oxide (IZO), Indium Gallium Zinc Oxide (IGZO), tantalum-doped tin oxide (SnO)₂Ta), niobium-doped tin oxide (SnO)₂Nb), tungsten-doped tin oxide (SnO)₂W), molybdenum-doped tin oxide (SnO)₂Mo), fluorine-doped tin oxide (SnO)₂F), or indium oxide doped with hydrogen (IOH). The transparent conductive oxide film may be a multilayer film having a plurality of films. The multilayer film may include, for example, a tin oxide film other than the above oxide film. The dopant In the tin oxide film is, for example, at least one selected from the group consisting of In, Si, Ge, Ti, Cu, Sb, Nb, F, Ta, W, Mo, Br, I, and Cl, and is not particularly limited. The photoelectric conversion layer 2 is preferably provided with a transparent layer including the first transparent electrode 1The electrically conductive oxide film is in direct contact.

Preferably, the first transparent electrode 1 includes a multi-layer structure in which an indium tin oxide film is laminated on a doped tin oxide film. Specifically, the first transparent electrode 1 preferably includes at least one multilayer structure selected from the group consisting of a multilayer film having an indium tin oxide film and an antimony-doped tin oxide film, a multilayer film having an indium tin oxide film and a fluorine-doped tin oxide film, a multilayer film having an indium tin oxide film and a tantalum-doped tin oxide film, and a multilayer film having an indium tin oxide film and a niobium-doped tin oxide film. If the first transparent electrode 1 includes a doped tin oxide film, the doped tin oxide film is preferably in direct contact with the photoelectric conversion layer 2.

The first transparent electrode 1 may include a metal film having a thickness of 10nm or less. The metal film is, for example, at least one film selected from the group consisting of Mo, Au, Cu, Ag, Al, Ta, Pt, Ru, and W, and is not particularly limited. Meanwhile, the first transparent electrode 1 may be an electrode having a dot-shaped, line-shaped or mesh-shaped metal on the upper or lower portion of the transparent conductive oxide film. At this time, a dot, line, or mesh metal is arranged between the transparent conductive oxide film and the photoelectric conversion layer 2. The dot-shaped, line-shaped, or mesh-shaped metal preferably has an aperture ratio of 50% or more with respect to the transparent conductive oxide film. The dot, line or network metal is, for example, Mo, Au, Cu, Ag, Al, Ta, Pt, Ru or W, and is not particularly limited. If a point-like, line-like or mesh-like metal is provided, transparency is ensured. Therefore, the thickness of the metal film is not limited.

From the viewpoint of improving the crystallinity of the photoelectric conversion layer 2, the surface of the first transparent electrode 1 on which the photoelectric conversion layer 2 is formed is preferably a metal oxide thin film (transparent conductive oxide film). The metal of the metal oxide containing Sn as a main component is preferably 90 atom% or more of Sn. The metal oxide thin film containing Sn as a main component includes at least one metal (metal oxide) selected from the group consisting of Zn, Al, Ga, In, Si, Ge, Ti, Cu, Sb, Nb, F, and Ta In addition to Sn. When the photoelectric conversion layer 2 is directly deposited on a metal oxide (e.g., ITO) film containing indium as a main component, the resulting multilayer including the ITO film and the substrateThe main body is easily deformed at high temperature. Therefore, it is not suitable for depositing Cu on an ITO film₂And (3) an O film.

The photoelectric conversion layer 2 is a p-type compound semiconductor layer mainly containing cuprous oxide. Cuprous oxide expressed as Cu₂O, an oxide semiconductor. The cuprous oxide is undoped or doped cuprous oxide. The photoelectric conversion layer 2 has a thickness of, for example, 500nm to 10 μm. The thickness of the photoelectric conversion layer 2 is preferably 1000nm to 5 μm, and more preferably 1500nm to 3 μm. The thickness of the photoelectric conversion layer 2 can be determined by, for example, observing the cross section.

Preferably, the photoelectric conversion layer 2 is rich in large cuprous oxide crystals and superior to a solar cell using the multilayer thin film 100 in conversion efficiency and light transmittance. If the process of this embodiment is used to fabricate the multilayer thin film 100, cuprous oxide crystals become large, contributing to improved conversion efficiency and light transmittance. Preferably, 95 wt% or more of the photoelectric conversion layer 2 includes cuprous oxide as a component. More preferably, 98 wt% or more of the photoelectric conversion layer 2 includes cuprous oxide as a component. That is, it is preferable that the photoelectric conversion layer 2 has almost (substantially) no heterogeneous phase such as CuO and/or Cu. If the photoelectric conversion layer 2 does not include any heterogeneous phase such as CuO and/or Cu, and is substantially Cu₂O single phase thin films are preferred because of their very high light transmittance. Photoelectric conversion layer 2 is substantially Cu₂This point of O single phase can be confirmed by measuring photoluminescence (PL method).

Preferably, the photoelectric conversion layer 2 includes Cu with a content of 60.0 atom% to 67.0 atom% and O (oxygen) with a content of 32.5 atom% to 34.0 atom%. In addition to Cu and oxygen, an element selected from the group consisting of a metal other than Cu, a dopant, and an impurity may be included. The photoelectric conversion layer 2 may include a metal other than copper as an oxide form, and the photoelectric conversion layer 2 may be a composite oxide. The metal contained In the photoelectric conversion layer 2 is at least one metal selected from the group consisting of Sn, Sb, Ag, Li, Na, K, Cs, Rb, Al, Ga, In, Zn, Mg, and Ca, In addition to copper. The band gap In the photoelectric conversion layer 2 can be adjusted if at least one metal selected from the group consisting of Ag, Li, Na, K, Cs, Rb, Al, Ga, In, Zn, Mg, Ta, and Ca is included In addition to copper. The first transparent electrode 1 side of the photoelectric conversion layer 2 may have a P + -type region in which at least one P-type dopant selected from Si, Ge, or N is dispersed at a high concentration.

The photoelectric conversion layer 2 preferably has a band gap of 2.0eV to 2.2 eV. The band gap in this range can effectively utilize sunlight in the top cell and the bottom cell of the multijunction solar cell, in which the solar cell using Si in the light absorbing layer is used as the bottom cell, and the solar cell using the thin film in this embodiment mode is used as the top cell. The composition of the photoelectric conversion layer 2 may be Cu_aM_bO_cAnd (4) showing. M is at least one element selected from the group consisting of Si, Ge, N, Sn, Sb, Ag, Li, Na, K, Cs, Rb, Al, Ga, In, Zn, Mg, Ta and Ca. Preferably, a, b and c satisfy 1.80. ltoreq. a.ltoreq.2.01, 0.00. ltoreq. b.ltoreq.0.20, and 0.98. ltoreq. c.ltoreq.1.02. The above composition ratio in the photoelectric conversion layer 2 is the composition ratio in the entire photoelectric conversion layer 2. Further, the above-described compound composition ratio in the photoelectric conversion layer 2 is preferably satisfied for the entire photoelectric conversion layer 2. The photoelectric conversion layer 2 may include an additional additive.

CuO-containing region 20 is present on the side having the n-type layer. The solar cell manufactured using the multilayer thin film 100 including the photoelectric conversion layer 2 having a very thin region containing CuO on the surface thereof has a higher open circuit voltage (Voc) than the solar cell manufactured using the multilayer thin film not containing the CuO region 20. The CuO-containing region 20 is a region up to a depth of 5nm in the inward direction of the photoelectric conversion layer 2 from the surface of the photoelectric conversion layer 2 opposite to the first transparent electrode 1 side. The CuO-containing region 20 contains 1.0 mol% or more CuO. Preferably, in the photoelectric conversion layer 2 excluding the CuO-containing region 20, Cu₂O relative to Cu₂O, CuO ratio of Cu ([ Cu ]₂Mass of O]/([Cu₂Mass of O]Quality of CuO]Quality of Cu]) ) from 99.5% to 100.0%. The CuO-containing region 20 is preferably present as only one thin surface region. Therefore, the CuO-containing region 20 is preferably a region up to a depth of 3nm inward of the photoelectric conversion layer 2 from the surface of the photoelectric conversion layer 2 opposite to the first transparent electrode 1 side, and more preferably a region up to a depth of 3nm inward of the photoelectric conversion layer 2 from the surface of the photoelectric conversion layer 2 opposite to the first transparent electrode 1 sideThe surface of (2) is directed inward of the photoelectric conversion layer 2 to a depth of 1 nm. In a region having a depth (starting point) of 20nm to a depth of 25nm in a direction from the surface of the photoelectric conversion layer 2 toward the first transparent electrode 1 side, it is preferable to have a CuO concentration of 0.5 mol% or less.

The CuO-rich ratio in the CuO-containing region 20 may be high due to the presence of CuO in the very thin region. With respect to CuO relative to Cu in CuO-containing region 20₂Ratio of O to CuO ([ moles of CuO in CuO-containing region 20 ]]/([ Cu in CuO-containing region 20)₂Mole number of O]+ [ moles of CuO in the CuO-containing region 20]) The content of CuO) is preferably 1.0 mol% to 100 mol%, and the content of CuO is more preferably 20 mol% to 100 mol%. Cu in CuO-containing region 20₂O relative to Cu₂Ratio of O to Cu ([ Cu in CuO-containing region 20)₂Mole number of O]/([ Cu in CuO-containing region 20)₂Mole number of O]+ [ moles of Cu in CuO-containing region 20]) Preferably 99.5 mol% to 100.0 mol% (excluding the case where the CuO-containing region 20 includes 100 mol% CuO). The composition of the photoelectric conversion layer 2 including the CuO-containing region 20 can be confirmed by XPS (x-ray photoelectron spectroscopy) or RBS (rutherford backscattering spectroscopy) analysis of the multilayer thin film 100.

Next, a process of manufacturing the multilayer film 100 will be described. Fig. 2 is a flow chart illustrating a process of manufacturing the multilayer thin film 100. This process of manufacturing the multilayer film 100 includes: a step (S01) of depositing Cu on the first transparent electrode 1₂A photoelectric conversion layer 2 containing O as a main component; and a step (S02) of setting the oxygen concentration of the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1at 5.0X 10^-3[Pa]To 5.0[ Pa ]]Is placed under the low-oxygen atmosphere (first atmosphere) for 1h to 1600 h. Before the step of depositing the photoelectric conversion layer 2 (S01), a decompression step (S00) may be optionally performed. In the step (S02) of placing the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 in a low-oxygen atmosphere (first atmosphere), the member is held in the low-oxygen atmosphere, for example. Hereinafter, for convenience, "placing the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 under a low-oxygen atmosphere" is expressed as the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 is kept under a low-oxygen atmosphereIn an atmosphere. The member is preferably maintained in a chamber in which the oxygen concentration and water vapour concentration are controlled.

Preferably, the photoelectric conversion layer 2 containing cuprous oxide as a main component is deposited by sputtering with copper as a target in an oxidizing atmosphere. The photoelectric conversion layer 2 is preferably deposited by sputtering at a high temperature. In the multilayer thin film 100 manufactured by the process of the present embodiment, Cu with a large grain size is contained in the photoelectric conversion layer 2₂O, which helps to improve the conversion efficiency of the solar cell.

The target material containing Cu as a main component contained Cu with a purity of 99.99%. The purity of Cu is preferably 99.995% or more, more preferably 99.999% or more. Using high purity Cu as a target material, Cu can be substantially formed₂O single-phase photoelectric conversion layer 2. If the target contains an element (e.g., Si) contained in the photoelectric conversion layer 2, the purity of copper is not limited to the above.

Preferably, the atmosphere during sputtering is an oxidizing atmosphere in which an inert gas and oxygen are mixed. More preferably, the atmosphere during sputtering is an atmosphere including an inert gas and oxygen. Preferable examples of the inert gas include nitrogen, argon, or a mixed gas of nitrogen and argon.

For example, sputtering is performed on a base material, wherein a first transparent electrode is formed on the glass base 10 or the like. Fig. 3 is a schematic cross-sectional view illustrating a multilayer film 100 including a substrate 10. Sputtering is performed on the surface of the first transparent electrode 1, so that the photoelectric conversion layer 2 is deposited on the first transparent electrode 1. Preferably, before sputtering, the reduction of the pressure in the chamber in which the first transparent electrode 1 is placed to 5.0X 10 is carried out^-3[Pa]Or lower (S00). The pressure reduction step (S00) may be performed in the chamber in which sputtering is performed, or may be performed in the sub-chamber. Unlike the sputtering step, no oxygen is injected during the depressurization step. The substrate 10 may be used as a substrate for a solar cell using the thin film 100. The first transparent electrode 1 is formed on the substrate 10 by, for example, sputtering. Preferred examples of the material of the substrate 10 used include glass such as white plate glass, soda lime glass, chemically strengthened glass, or quartz glass. In addition, organic materials such as acrylics, polycarbonsAcid esters or polyimides may also be used for the substrate 10.

Cu₂The thickness of the O (photoelectric conversion layer 2) film may be set to T. In this case, preferably, Cu₂The average diameter of the O crystal in the film thickness direction of the photoelectric conversion layer 2 is 0.7T to 1.0T, excluding Cu having a diameter of 50nm or less in the film thickness direction₂Microscopic Cu of O crystal₂And (4) an O phase. When microscopic Cu₂When the O phase is rich, the number of grain boundaries is large, which may cause a decrease in conversion efficiency. Preferably, Cu having a diameter of 50nm or less in the film thickness direction₂Microscopic Cu of O crystal₂The sectional area of the O phase accounts for 10% or less of the sectional area of the photoelectric conversion layer 2. The photoelectric conversion layer 2 may include small grain size Cu₂And (4) O crystals. In this case, during the following step maintained under a low oxygen atmosphere, oxidation proceeds at a deep portion of the photoelectric conversion layer 2. This generates a heterogeneous phase, resulting in a decrease in crystallinity of the photoelectric conversion layer 2. From the viewpoint of limiting the region having CuO-containing region 20 to the very thin surface region of photoelectric conversion layer 2, it is preferable to contain much large Cu₂And (4) O crystals. Specifically, it is preferable that crystals having a diameter of 50nm or less account for 10% or less of the cross-sectional area of the photoelectric conversion layer 2. The absorption band of CuO coincides with that of a solar cell using Si. From the viewpoint of applying the multilayer thin film 100 in the present embodiment to a multijunction solar cell, the photoelectric conversion layer 2 preferably has Cu with a large grain size₂O。

In addition, when the photoelectric conversion layer 2 is deposited on the metal oxide film containing Sn as a main component, Sn is present in Cu₂Cu in O film deposition process₂Diffusion in the O film. This makes the grain size larger than when sputtering on a glass substrate at the same temperature, thereby enabling an increase in crystallinity. When heated, Cu₂O is sputtered on a metal oxide film containing Sn as a main component, thereby allowing Cu having a size grown to be equivalent to the film thickness₂Cu of O crystal₂And (4) depositing an O film. This cannot be achieved by sputtering without heating. As described above, the Cu₂O film is substantially Cu₂O single phase and thus as a photoelectric conversion of transparent solar cellsThe layer is desirable because the entire film has good crystallinity.

The copper sheet is oxidized at high temperature, and thick Cu can be deposited₂O film of Cu₂O grows to a size comparable to the film thickness. Also in this case, after the Cu plate is oxidized, after the Cu is oxidized₂And forming a transparent electrode on the O film. If the transparent electrode is formed directly on Cu by sputtering₂Cu formed on the O film₂The O crystals are disintegrated. This results in a reduction in power generation efficiency when manufacturing a solar cell. The multilayer thin film in the present embodiment is obtained by depositing the photoelectric conversion layer 2 on the transparent electrode 1. Therefore, after the solar cell is manufactured, the photoelectric conversion layer 2 of high quality can be maintained.

In the present embodiment, the photoelectric conversion layer 2 is not deposited on the glass substrate, but the photoelectric conversion layer 2 is deposited on the first transparent electrode 1. If the photoelectric conversion layer 2 is deposited on the glass substrate, impurities present in the glass diffuse to the photoelectric conversion layer 2. This may cause a change in film deposition conditions or degrade the film quality of the photoelectric conversion layer 2 due to the formation of impurity levels. In addition, if the photoelectric conversion layer 2 is deposited on a metal film that can be used as an electrode, the resulting multilayer thin film 100 does not have light transmittance. In this embodiment mode, light transmittance is an essential feature. Therefore, a multilayer thin film obtained by depositing the photoelectric conversion layer 2 on the metal film is impractical from the viewpoint of light transmittance. There is little problem if a portion of the glass appears after scribing. The case of using the cuprous oxide solar cell alone is not applicable to the above case.

Optionally post-sputter heating. The heating is preferably performed while the multilayer structure is maintained in the chamber from room temperature to the sputtering temperature for a desired period of time.

Next, the holding step under a low oxygen atmosphere (S02) will be described. The member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 is kept under a low oxygen atmosphere. The maintenance in a low oxygen atmosphere enables the formation of the CuO-containing region 20 in a very thin surface region of the photoelectric conversion layer 2. The low oxygen atmosphere preferably has an oxygen concentration (mass/volume) of 5.0X 10^-8[g/L]To 5.0X 10^-5[g/L]More preferably, the atmosphere ofIt is preferable that the oxygen concentration is 5.0X 10^-8[g/L]To 3.5X 10^-5[g/L]Of the atmosphere (c). The member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 under a low oxygen atmosphere can be maintained under a low oxygen atmosphere. This enables the CuO-containing region 20 to be formed in a very thin surface region of the photoelectric conversion layer 2. If this member is held for a short time in an atmosphere of high oxygen concentration, for example, an air atmosphere, a very thin CuO-containing region 20 is not formed on the surface of the photoelectric conversion layer 2. In contrast, if the member is held in an atmosphere of high oxygen concentration, for example, an air atmosphere, for a long time, not only the surface but also the inner portion of the photoelectric conversion layer 2 has CuO. Therefore, before the step of maintaining the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 under the low oxygen atmosphere (S02), the step of leaving the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 under an air atmosphere (second atmosphere) of 0 ℃ to 50 ℃ for 1 hour or less (S03) is performed.

The low oxygen atmosphere selectively contains ozone. The oxygen concentration is the sum of the concentrations of oxygen molecules and ozone molecules. For example, the oxygen concentration and the water vapor concentration in the air may be reduced to form a low oxygen atmosphere. If a large amount of other oxidizing and/or reducing gases is contained in the low-oxygen atmosphere, Cu is oxidized properly₂The very thin surface area of the O-film is not suitable. Therefore, in the case of obtaining a low oxygen atmosphere from the air, it is preferable that the inert gas occupies the total pressure [ Pa ] of the low oxygen atmosphere]95% or more; more preferably, the inert gas occupies the total pressure [ Pa ] of the low-oxygen atmosphere]99% or more; further preferably, the inert gas occupies the total pressure [ Pa ] of the low-oxygen atmosphere]99.9% or more. Note that carbon dioxide is acidic and does not readily oxidize Cu₂And O. Therefore, the carbon dioxide concentration is not particularly limited.

The total pressure of the low-oxygen atmosphere is not particularly limited. When a low oxygen atmosphere is obtained by reducing the oxygen concentration in the air, it is typical that the total pressure is preferably set to 8.0 × 10⁴[Pa]To 1.2X 10⁵[Pa]. If the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 in the vacuum chamber is kept under a low oxygen atmosphere, the low oxygen atmosphereTotal pressure of (2) is preferably 100[ Pa ]]Or lower.

The member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 can be collected from the film deposition chamber in which the photoelectric conversion layer 2 has been deposited on the first transparent electrode 1, and is carried from the air atmosphere and then is kept in the low-oxygen atmosphere. In this case, it is preferable to reduce the oxygen concentration and the water vapor concentration so that the above or below-described atmosphere is achieved within one hour after the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 is conveyed to the chamber of the low oxygen atmosphere.

Meanwhile, the member having the photovoltaic conversion layer 2 formed on the first transparent electrode 1 may be maintained under a low oxygen atmosphere. The holding time is preferably from 1h to 1600 h. When the retention time is less than 1h, little CuO is generated. Further, even if the holding time is extended, the further increase in the open circuit voltage is small. In addition, prolonged holding times have a greater impact on productivity. The holding time is then preferably from 1h to 1600 h.

The water vapor concentration (mass/volume) in the low-oxygen atmosphere is preferably 5.0X 10 during the step of maintaining under the low-oxygen atmosphere^-8[g/L]To 5.0X 10^-5[g/L]And more preferably 5.0 × 10^-8[g/L]To 4.0X 10^-5[g/L]. If the water vapor concentration in the low oxygen atmosphere is high, oxidation may proceed and the deep portion of the photoelectric conversion layer 2 is also easily oxidized. Then, the photoelectric conversion layer 2 is preferably kept in an atmosphere having a low water vapor concentration and a low oxygen concentration.

In the maintaining step under the low oxygen atmosphere, the temperature of the low oxygen atmosphere is preferably 0 ℃ to 100 ℃. If the temperature is too low when the substrate is kept in a low oxygen atmosphere, Cu on the surface of the photoelectric conversion layer 2 is difficult to form₂And oxidizing O. In contrast, if the temperature is too high when kept in a low oxygen atmosphere, an oxidation reaction occurs even in the deep portion of the photoelectric conversion layer 2. Therefore, a reaction similar to that during a long-term holding in air occurs. Therefore, during the maintaining step of the low-oxygen atmosphere, the temperature of the low-oxygen atmosphere is preferably 0 ℃ to 50 ℃.

If the oxygen concentration, the water vapor concentration, and the temperature are close to the lower limit of the above ranges, oxidation of the surface of the photoelectric conversion layer 2 does not easily proceed. In addition, CuO is generated very little in a short time, and thus Voc is hardly increased. Therefore, the holding time under the low oxygen atmosphere is preferably 72 to 1600 hours.

If the oxygen concentration, the water vapor concentration, and the temperature approach the upper limit of the above ranges, the surface of the photoelectric conversion layer 2 is excessively oxidized. Therefore, the film quality of the photoelectric conversion layer 2 is degraded in some cases. Therefore, the holding time in the low oxygen atmosphere is preferably 1 to 1000 h.

The holding time in a low oxygen atmosphere is preferably 72h to 1000h, more preferably 500h to 1000h, from the viewpoint of appropriately oxidizing the very thin surface region of the photoelectric conversion layer 2.

The holding time in the low oxygen atmosphere during the holding step under the low oxygen atmosphere is defined as t [ h ]]The oxygen concentration in a low oxygen atmosphere is defined as C_o(g/L) and the water vapor concentration in the low oxygen atmosphere is defined as C_w(g/L), preferably satisfies 1.0X 10^-7[h·g/L]≤t×C_o[h·g/L]≤1.6×10^-3[h·g/L]And 1.0X 10^-7[h·g/L]≤t×C_w[h·g/L]≤6.5×10^-2[h·g/L](ii) a More preferably 1.0X 10^-6[h·g/L]≤t×C_o[h·g/L]≤2.5×10^-4[h·g/L]And 1.0X 10^-6[h·g/L]≤t×C_w[h·g/L]≤2.0×10^-3[h·g/L](ii) a And further preferably satisfies 1.0X 10^-5[h·g/L]≤t×C_o[h·g/L]≤2.5×10^-4[h·g/L]And 5.0X 10^-5[h·g/L]≤t×C_w[h·g/L]≤2.5×10^-4[h·g/L]. If the oxygen concentration and the water vapor concentration are high, CuO is likely to be formed on the surface of the photoelectric conversion layer 2 even with a short retention time. If the oxygen concentration and the water vapor concentration are low, a longer retention time easily causes CuO to be formed on the surface of the photoelectric conversion layer 2, thereby increasing Voc when manufacturing a solar cell. In view of the oxygen concentration and the water vapor concentration, the holding time preferably satisfies the above range. The product of time and oxygen concentration or water vapor concentration refers to the product of time and average oxygen concentration or average water vapor concentration during the holding in the low-oxygen atmosphere.

The oxygen concentration in the gas (low-oxygen atmosphere) can be determined from the oxygen concentration in the gas by using, for example, a galvanic oxygen sensor or a zirconia sensor. Furthermore, the water vapour concentration in the gas (low oxygen atmosphere) can be determined from the measured dew point and temperature by using, for example, a capacitive or specular reflection dew point meter.

Before the step of maintaining the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 under the low oxygen atmosphere (S02), a step of leaving the member having the photoelectric conversion layer 2 formed on the first transparent electrode 1 under an air atmosphere (second atmosphere) of 0 ℃ to 50 ℃ for 1 hour or less is performed (S03).

The light transmittance of the multilayer film 100 produced by this process is 50% or more at a wavelength of 700nm to 1000 nm. Therefore, the multilayer film 100 has excellent light transmittance. The multi-layered thin film 100 having excellent light transmittance is suitable for a top cell of a light-transmitting solar cell and/or a multijunction solar cell, in which even a bottom cell can efficiently generate electricity.

(second embodiment)

The second embodiment pertains to a solar cell and a method of manufacturing a solar cell. Fig. 4 is a schematic cross-sectional view illustrating the solar cell 200. As shown in fig. 4, the solar cell 200 includes: a first transparent electrode 1; a photoelectric conversion layer 2; an n-type layer 3; and a second transparent electrode 4. The multilayer body obtained by stacking the first transparent electrode 1 and the photoelectric conversion layer 2 is the multilayer thin film 100 in the first embodiment. The photoelectric conversion layer 2 is disposed between the first transparent electrode 1 and the n-type layer 3. The n-type layer 3 is disposed between the photoelectric conversion layer 2 and the second transparent electrode 4. The photoelectric conversion layer 2 and the n-type layer 3 are used to form a p-n junction. The first transparent electrode 1 and the photoelectric conversion layer 2 are the same as those of the first embodiment, and therefore, description thereof is omitted. For example, an intermediate layer (not shown) may be disposed between the n-type layer 3 and the second transparent electrode 4. The multijunction solar cell may be manufactured by stacking the solar cell 200 in the second embodiment on a solar cell (e.g., Si solar cell) having a photoelectric conversion layer with a narrower band gap than the photoelectric conversion layer 2.

The n-type layer 3 is an n-type semiconductor layer. The n-type layer 3 is disposed between the photoelectric conversion layer 2 and the n-electrode 4. n-type layer 3 andthe surface of the p-type light absorbing layer 2, which is opposite to the surface contacting the first transparent electrode 1, is in direct contact. The n-type layer 3 is preferably a layer comprising an oxide layer and/or a sulfide layer. More specifically, the oxide layer used in the n-type layer 3 is preferably selected from Zn_(1-x)A_xO_y(A ═ Si, Ge or Sn, x ≦ 0.6, y ≦ 0.9 ≦ 1.1), Cu_(2-x)M_xO (M ═ Mn, Mg, Ca, Zn, Sr or Ba, 0. ltoreq. x.ltoreq.0.3), A_(2-x-y)Al_yGa_xO₃(A ═ Si, Ge or Sn, 1.3. ltoreq. x.ltoreq.2, 0. ltoreq. y.ltoreq.0.7, x + y. ltoreq.2) and Al_(2-x)Ga_xO₃(1.3. ltoreq. x. ltoreq.2). The sulfide layer used in the n-type layer 3 is preferably selected from Zn_xIn_(2-2x)S_(3-2x)(x is more than or equal to 1 and less than or equal to 1.5), ZnS and In_xGa_(1-x)S (0. ltoreq. x. ltoreq.1). The n-type layer 3 may have a multilayer structure obtained by laminating the above-described oxide layer and/or sulfide layer.

The n-type layer 3 typically has a film thickness of 5nm to 100 nm. If the thickness of the n-type layer 3 is equal to or less than 5nm, a leakage current occurs when the coverage of the n-type layer 3 is poor. This may result in degradation of characteristics. When the coverage is good, the film thickness is not limited to the above. If the thickness of the n-type layer 3 exceeds 100nm, a characteristic degradation may result due to excessively high resistance of the n-type layer 4, or a short-circuit current reduction may result due to a reduction in light transmittance. Therefore, the thickness of the n-type layer 3 is preferably 10nm to 50 nm. Further, in order to realize a film having a good coverage, the surface roughness of the n-type layer 3 is preferably 5nm or less. When the n-type layer 3 has high quality, the solar cell can be operated even at a film thickness of about 200 nm.

The conduction band offset (Δ E ═ Ecp-Ecn) refers to the difference between the potential (Ecp (eV)) of the Conduction Band Minimum (CBM) of the photoelectric conversion layer 2 and the potential (Ecn (eV)) of the conduction band minimum of the n-type layer 3, and is preferably-0.2 eV to 0.6eV (-0.2eV ≦ Δ E ≦ +0.6 eV). If the conduction band offset is greater than 0, the conduction band at the p-n junction interface is discontinuous and spikes (spikes) occur. When the conduction band offset is less than 0, the conduction band of the p-n junction interface is discontinuous and a notch (cliff) occurs. Both the peaks and the notches are barriers to photo-generated electrons. Therefore, the smaller the size, the better. Therefore, the conduction band offset is preferably 0.0eV to 0.4eV (0.0 eV. ltoreq. DELTA.E. ltoreq. +0.4 eV). In this respect, the above does not apply to the case of conduction using an energy level within the gap. The potential of the CBM can be estimated using the following steps. Photoelectron spectroscopy is a method of evaluating electron occupied energy levels for the actual measurement of the valence band top (VBM). Next, the band gap of the measured material is estimated. The CBM is then calculated. However, for a practical p-n junction interface, the ideal interface cannot be maintained due to interdiffusion and/or the presence of cationic holes. This is highly likely to cause a change in the band gap. For the reasons described above, it is preferable to directly evaluate CBM using reverse photoelectric emission spectroscopy using a photoelectron emission inversion process. Specifically, the electronic state of the p-n junction interface can be assessed by repeating photoelectron/inverse photoelectron spectroscopy and low energy ion etching of the solar cell surface.

Before the n-type layer 3 is formed, it is preferably kept in an air atmosphere at 0 to 50 ℃ for 1 hour or less, and if the holding time in the air atmosphere is prolonged, the inside of the photoelectric conversion layer 2 is oxidized. This is not preferred. Preferably, the n-type layer 3 is formed immediately after the multilayer film 100 is manufactured.

The second transparent electrode 4 preferably uses a transparent conductive oxide film represented by the first transparent electrode 1 or a multilayer body thereof.

In the second embodiment, the process of manufacturing the multilayer thin film 100 according to the first embodiment should be employed. This makes it possible to manufacture a solar cell having excellent light transmittance. A film having excellent light transmittance can be used for the photoelectric conversion layer 2, and a film having high light transmittance can also be deposited like other layers. This makes it possible to manufacture a solar cell having excellent light transmittance.

(third embodiment)

The third embodiment pertains to a multijunction solar cell. Fig. 5 is a schematic cross-sectional view illustrating a multijunction solar cell in a third embodiment. The multijunction solar cell 200 in fig. 5 includes: the solar cell (first solar cell) 200 in the second embodiment disposed on the light incident side; and a second solar cell 201. The first solar cell 200 is manufactured using the multilayer thin film 100 manufactured by the process of the first embodiment. The band gap in the light absorbing layer of the second solar cell 201 is smaller than that in the photoelectric conversion layer 2 of the solar cell 200 in the second embodiment. Note that examples of the multijunction solar cell in the present embodiment include a solar cell in which three or more solar cells are connected.

The band gap of the photoelectric conversion layer of the multilayer thin film 100 in the first embodiment is about 2.0eV to 2.2 eV. Therefore, the band gap in the light absorbing layer of the second solar cell 201 is preferably 1.0eV to 1.6 eV. The light absorbing layer In the second solar cell is preferably one selected from the group consisting of perovskite compounds, crystalline silicon, and at least one compound semiconductor selected from CIGS-and CdTe-based compounds having a high In content ratio.

(fourth embodiment)

The fourth embodiment pertains to a solar cell module. Fig. 6 is a perspective view illustrating a solar cell module 300 in the fourth embodiment. In the solar cell module 300 in fig. 6, a first solar cell module 301 and a second solar cell module 302 are stacked. The first solar cell module 301 is placed on the light incident side, and uses the solar cell 200 manufactured by the multilayer thin film 100 manufactured by the process of the first embodiment. It is preferable to use the second solar cell 201 for the second solar cell module 302.

Fig. 7 is a sectional view illustrating a solar cell module 300. In fig. 7, the structure of the first solar cell module 301 is described in detail, but the structure of the second solar cell module 302 is not illustrated. In the second solar cell module 302, the structure of the solar cell module is suitably selected depending on, for example, a light absorbing layer in the solar cell used. The solar cell module shown in fig. 7 includes a plurality of subassemblies 303, and the subassemblies 303 are framed by broken lines and electrically connected in series using wiring 304 so that a plurality of solar cells 200 (solar cells) are horizontally arranged. The plurality of subassemblies 303 are electrically connected in parallel or in series. Adjacent subassemblies 303 are electrically connected by bus bars 305.

The adjacent solar cells 200 are arranged such that the second transparent electrode 4 on the upper side thereof is connected to the corresponding first transparent electrode 1 on the lower side thereof using the wiring 304. Both ends of the solar cell 200 in the subassembly 303 are connected to the bus bar 305. The bus bar 305 is configured to electrically connect the plurality of subassemblies 303 in parallel or series to adjust the voltage output to or from the second solar cell assembly 302. Note that how the solar cell 200 is connected as explained in the fourth embodiment is an example. Therefore, the solar cell module may be configured to use other connection means.

(fifth embodiment)

The fifth embodiment belongs to a photovoltaic power generation system. The solar cell module in the fourth embodiment may be used as a generator for generating electricity in the photovoltaic power generation system in the fifth embodiment. The photovoltaic power generation system in the present embodiment generates power using the solar cell module, and specifically includes: a solar cell module configured to generate electricity; a unit configured to convert the generated power; and a power storage unit configured to store the generated power or a load configured to consume the generated power. Fig. 8 is a diagram illustrating the structure of the photovoltaic power generation system 400 according to the present embodiment. The photovoltaic power generation system in fig. 8 includes a solar cell module 401(300), a converter 402, a storage battery 403, and a load 404. Either the battery 403 or the load 404 may be omitted. The load 404 may be configured to be able to utilize the electrical energy stored in the battery 403. Converter 402 is a device having circuitry or components configured to perform power conversion, such as voltage conversion or DC-AC conversion, including a DC-DC converter, a DC-AC converter, or an AC-AC converter. As the configuration of the converter 402, an appropriate configuration may be adopted according to the configuration of the generated voltage, the battery 403, and the load 404.

The solar cell included in each light-receiving sub-assembly 301 included in the solar cell module 300 can generate electricity. This electric energy is converted by the converter 402 and stored in the battery 403 or consumed in the load 404. Preferably, the solar cell module 401 is provided with a solar light tracking device configured to continuously guide the solar cell module 401 to the sun, is further mounted with a condenser to condense the solar light, and/or is additionally provided with a device for improving the power generation efficiency, for example.

Preferably, the photovoltaic power generation system 400 is used for real estate such as residences, commercial facilities, or factories, or for mobile property such as vehicles, airplanes, electronic devices, and the like. In the above-described embodiments, the use of the photoelectric conversion element for a solar cell module and having excellent conversion efficiency should increase the amount of power generation.

As an example of using the photovoltaic power generation system 400, a vehicle is shown. Fig. 9 is a schematic diagram illustrating a vehicle 500. The vehicle 500 in fig. 9 includes a vehicle body 501, a solar cell module 502, a power converter 503, a storage battery 504, a motor 505, and tires (wheels) 506. Electric power generated in a solar cell module 502 provided in an upper portion of the vehicle body 501 is converted by a power converter 503, and the generated electric power is charged in a storage battery 504 or consumed in a load such as a motor 505. When tires (wheels) 506 are rotated by the motor 505, electric power supplied from the solar cell module 502 or the storage battery 504 can be used to drive the vehicle 500. The solar cell module 502 is not necessarily a multi-junction type, and may be constituted only by the first solar cell module including, for example, the solar cell 200 in the second embodiment. If the transparent solar cell module 502 is employed, the solar cell module 502 is preferably used as a power generation window provided on the side of the vehicle body 501 and the top of the vehicle body 501.

The present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[ examples ]

(example 1)

An ITO transparent conductive film as a first transparent electrode on the back side is first deposited on a white board glass substrate in a chamber, and then Sb-doped SnO is deposited thereon₂A transparent conductive film. The pressure of the chamber in which the transparent member having the first transparent electrode is placed is reduced to 1 × 10^-3[Pa]Or smaller. Next, a cuprous oxide compound was deposited thereon as a 2 μm photoelectric conversion layer by sputtering in an oxygen and argon atmosphere. The resultant member was kept in an air atmosphere at 25 ℃ for 30 minutes and then kept in a low-oxygen atmosphere created by reducing the oxygen and water vapor concentrations in the air1h (temperature 25 ℃, oxygen concentration 1.5X 10)^-7(g/L) and a water vapor concentration of 1.2X 10^-6(g/L) atmosphere). Subsequently, n-type Zn_0.8Ge_0.2O is deposited on the p-type cuprous oxide layer by room temperature sputtering. After that, an AZO transparent conductive film is deposited as the second transparent electrode on the surface side. Finally, MgF₂Deposited thereon as an anti-reflection film.

(examples 2 to 41, reference example 1 and comparative examples 1 to 5)

The tables in fig. 10 and 11 collectively provide examples, reference examples, and comparative examples. As in example 1, the solar cells in examples 2 to 41, reference example 1 and comparative examples 1 to 5 were manufactured under the conditions specified in the tables of fig. 10 and 11. Note that In example 41 and comparative example 5_0.7Ga_0.3S instead of n-type Zn_0.8Ge_0.2O is deposited on the p-type cuprous oxide layer.

Before the n-type layer film deposition, the presence or absence of CuO was confirmed by XPS detection of a region 1nm deep from the surface of the photoelectric conversion layer. When the CuO content was found to be 20 mol% to 100 mol% in a region 1nm deep from the surface of the photoelectric conversion layer, the classification was A. When the CuO content of the domain was found to be 1 mol% to less than 20 mol%, it was classified as B. When the CuO content of the domain is found to be less than 1 mol%, it is classified as C. Further, Voc is calculated from the obtained conversion efficiency of each solar cell. When Voc is 0.95V or higher, it is rated A. When Voc is from 0.85V to less than 0.95V, it is rated as B. When Voc is less than 0.85V, it is rated as C. The light transmittance at a wavelength of 700nm to 1000nm through each of the solar cells obtained was further evaluated. When the light transmittance through the obtained solar cell at a wavelength of 700nm to 1000nm was 50% or more, it was rated as a. When the light transmittance was 10% to less than 50%, it was rated as B. When the transmittance was less than 10%, it was rated as C. The results are shown in the table of fig. 12.

CuO up to 1nm in thickness can be generated in a very thin region by maintaining the sample in an atmosphere of low oxygen and water vapor concentration for a long time. Similarly, CuO is also generated if the sample is kept in an atmosphere of high oxygen and water vapor concentrations for a long time. However, CuO is generated in a deeper region, which results in a voltage reduction.Therefore, in an atmosphere of low oxygen and water vapor concentration, Cu is transferred for a considerable time₂The conversion of O to CuO seems better.

When the retention time in the low-oxygen atmosphere was about 0.5h, no formation of CuO on the surface of the photoelectric conversion layer was detected. However, when the retention time was 1h or 10h, the formation of a small amount of CuO was detected. When the sample is maintained in a low oxygen atmosphere for 72h or more, a large amount of CuO is selectively formed in a very thin surface region of the photoelectric conversion layer. At this time, the sample was exposed to air at room temperature for 0.5h before the sample was maintained in a low oxygen atmosphere. The copper oxide can be sufficiently formed by maintaining the low oxygen atmosphere for a long time. However, when the sample was kept in a low oxygen atmosphere for 2000h as in the reference example, no further increase in Voc was observed. Therefore, it is uneconomical to maintain 2000h for a long time. But from the viewpoint of increasing Voc, retention is a suitable process.

As shown in examples 9 to 22, CuO can be formed in a very thin region and Voc increases even when the oxygen concentration and the water vapor concentration are changed. As shown in examples 23 to 24, CuO can be formed in a very thin surface region as in the other examples even when the product of oxygen concentration (water vapor concentration) and time is very large. As shown in comparative example 2, CuO cannot be formed when the oxygen concentration is too low. As shown in comparative examples 3 to 4, when the oxygen concentration is too high, Voc is reduced due to excessive oxidation while CuO is formed.

As shown in examples 25 to 27, CuO may be formed when the temperature is changed from 0 ℃ to 100 ℃. The formation rate of CuO is slow at low temperatures and fast at high temperatures. Therefore, it is preferable to adjust the oxygen concentration, the water vapor concentration, and the time within the above ranges according to the temperature.

Further, as shown in examples 28 to 31, even if the air exposure condition is changed, oxidation does not proceed in a deeper region of the photoelectric conversion layer unless a long-time treatment is performed at a higher temperature. The temperature in example 29 was high. In addition, the time in example 31 was long. Therefore, oxidation proceeds in a deeper region of the photoelectric conversion layer than in the other embodiments. This does not have the deleterious effect of, for example, reducing Voc.

In examples 32 and 33, the holding time was 72h, a higher oxygen concentration was used, and the water vapor concentration was varied. In either embodiment, CuO is present relatively abundantly in the very thin surface region of the photoelectric conversion layer; no copper oxide is generated in a deeper area; this increases Voc. In example 34, a higher oxygen concentration than in example 32 was used, and the retention time was 50 h. Although the amount of copper oxide produced was smaller than in examples 32 and 33, the amount of copper oxide produced was relatively rich. So Voc increases.

Further, even if the air exposure conditions were changed as in examples 35 to 39, oxidation did not proceed in the deep region of the photoelectric conversion layer unless long-term treatment was performed at a higher temperature. In example 36, the temperature was high. In addition, the time in example 39 was long. Therefore, oxidation proceeds in a deeper region of the photoelectric conversion layer than in the other embodiments. This does not have the deleterious effect of, for example, reducing Voc.

In example 40, the total pressure was lower than the atmospheric pressure. CuO is also formed in a very thin surface region of the photoelectric conversion layer even if the total pressure is low. In example 41 and comparative example 5, the n-type layer was composed of sulfide. Good results are obtained even if the n-type layer is not made of an oxide.

In example 41, although the retention time was short, the oxygen concentration increased. Therefore, the CuO ratio is as high as when it is maintained for a long period of time. Furthermore, Voc is excellent.

In the specification, some elements are represented by chemical symbols of the elements only.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Description of the symbols

100 multilayer film

1 first transparent electrode

2 photoelectric conversion layer

3N type layer

4 second transparent electrode

10 base

200 solar energy battery (first solar battery)

201 second solar cell

300 solar cell module

301 first solar cell module

302 second solar cell module

303 sub-assembly

304 bus

400 photovoltaic power generation system

401 solar cell module

402 converter

403 accumulator

404 load

500 vehicle

501 vehicle body

502 solar cell module

503 power converter

504 accumulator

505 electric machine

506 tyres (wheels).