JP2010258255A - Anodic oxidation substrate, method of manufacturing photoelectric conversion element using the same, the photoelectric conversion element, and solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress corrosion of a surface of an anodic oxidation substrate due to an alkaline solution in the anodic oxidation substrate for a photoelectric conversion element. <P>SOLUTION: In the anodic oxidation substrate 10a in which an anodic oxidation film 12 is formed on an Al base material 11, an alkali-proof substrate protective film 13 is formed on a surface opposite to the side on which a laminated structure such as a photoelectric conversion layer or the like is formed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an anodized substrate for a photoelectric conversion element having an anodized film as an insulating layer on the surface, a method for producing a photoelectric conversion element using the same, a photoelectric conversion element, and a solar cell.

  Currently, research on solar cells is actively conducted. In general, a solar cell is connected to a plurality of photoelectric conversion elements in which a laminated structure of a lower electrode (back electrode), a photoelectric conversion layer that generates current by light absorption, and an upper electrode (transparent electrode) is formed on a substrate. To be used.

  Conventionally, as the photoelectric conversion layer of the photoelectric conversion element, bulk single crystal Si or polycrystalline Si, or thin film amorphous Si has been mainly used, but in recent years, a compound semiconductor independent of Si is used for the photoelectric conversion layer. Research and development has been done. As such a compound semiconductor solar cell, a CIS (Cu-In-Se) system or CIGS (Cu-In-Ga) system comprising a bulk system such as a GaAs system and a group Ib element, group IIIb element and group VIb element. -Se) and other thin film systems are known. CIS-based or CIGS-based solar cells have high light absorptance, and high photoelectric conversion efficiency has been reported.

  Moreover, as a substrate of a photoelectric conversion element, a glass substrate is mainly used, but the use of a flexible metal substrate has been studied. A solar cell using a metal substrate may be applicable to a wider range of uses than a glass substrate because of the light weight and flexibility of the substrate. Furthermore, since the metal substrate can withstand high-temperature processes, the photoelectric conversion characteristics are improved, and further improvement in photoelectric conversion efficiency of the solar cell can be expected.

In the case of using a metal substrate, it is necessary to provide an insulating layer on the surface of the substrate so that a short circuit between the substrate and the electrode and photoelectric conversion layer formed on the substrate does not occur. Therefore, Patent Document 1 proposes to use an anodized substrate in which an anodized film (Al ₂ O ₃ ) as an insulating layer is formed on the surface of an Al base as a substrate of a solar cell. In this method, even when a large-area substrate is used, an insulating layer having no pinholes on the entire surface and having high adhesion can be easily formed.

  For example, in the case of forming a CIS-based or CIGS-based solar cell using the anodized substrate as described above, the structure is generally as shown in FIG. As shown in FIG. 9, the CIS or CIGS solar cell in this case includes an anodized substrate 19, a lower electrode 29, a photoelectric conversion layer 39, and a high-resistance buffer formed on the anodized substrate 19. A layered structure of the layer 49 and the upper electrode 59 is formed. The buffer layer 49 is for improving electrical contact between the photoelectric conversion layer 39 and the upper electrode 59, and insertion of the buffer layer 49 can be expected to improve photoelectric conversion efficiency. At present, a CdS buffer layer manufactured by a chemical bath deposition (CBD) method is considered to be most suitable as the buffer layer 49 of a CIS or CIGS solar cell.

JP 2000-349320 A

  However, in the solar cell as described above, when the CdS buffer layer is formed by the CBD method, the back surface of the anodized substrate is corroded by an alkali solution and cracks are generated, so that the internal stress on the back surface side is released and the substrate is warped. Is generated, and there is a problem that cracks and peeling occur in the photoelectric conversion layer and the lower electrode. This is presumably because the back surface of the anodized substrate has poor alkali resistance.

  As described above, when cracking or peeling occurs in the photoelectric conversion layer, the lower electrode, or the like, the photoelectric conversion characteristics of the solar cell may be deteriorated, so that it is necessary to suppress the corrosion of the back surface of the anodized substrate.

  The present invention has been made in view of the above problems, and in an anodized substrate in which an anodized film is formed on an Al base and a method for manufacturing a photoelectric conversion element using the same, an alkaline solution on the back surface of the anodized substrate is used. An object of the present invention is to provide a photoelectric conversion element having good photoelectric conversion characteristics and an anodized substrate capable of manufacturing a solar cell, which suppresses corrosion, and a method for manufacturing a photoelectric conversion element using the same. .

  Another object of the present invention is to provide a photoelectric conversion element and a solar cell having good photoelectric conversion characteristics in a photoelectric conversion element and a solar cell using an anodized substrate in which an anodized film is formed on an Al base material. It is what.

In order to solve the above problems, an anodized substrate for a photoelectric conversion element according to the present invention is:
In an anodized substrate in which an anodized film is formed on both sides of an Al base material,
A substrate protective layer having alkali resistance is provided on one anodic oxide film.

  Here, “Al substrate” means a metal substrate having an Al content of 90% by mass or more. The Al base material may be a pure Al base material that may contain a trace element, or an alloy base material of Al and another metal element.

  “Alkali resistance” of the substrate protective layer means that the film thickness of the substrate protective layer when immersed in an alkaline solution of pH 11 for 15 minutes is 1/10 or less of the film thickness, and the substrate protective layer does not crack. It shall mean a degree of resistance.

Furthermore, in the anodized substrate for a photoelectric conversion element according to the present invention, the thermal expansion coefficient of the main component of the substrate protective layer is preferably substantially equal to the thermal expansion coefficient of Al ₂ O ₃ .

  Here, the “thermal expansion coefficient” means the linear expansion coefficient of the bulk body at 500 K, which is a substantially intermediate temperature between the growth temperature of the photoelectric conversion layer and room temperature.

The coefficient of thermal expansion is “substantially equivalent” means that the linear expansion coefficient of Al ₂ O _{3 at} 500 K is 7.5 × 10 ⁻⁶ / K, so that the linear expansion coefficient of the substrate protective layer is ± 5. within the scope of 0 × ^{10 -6} / K, shall mean i.e. in the range of ^{2.5 × 10 -6 /K~12.5×10 -6 / K} .

The substrate protective layer is preferably an insulating film. In this case, the insulating film is mainly composed of at least one selected from the group consisting of soda lime glass, SiO ₂ , TiO ₂ , TiN, and Al ₂ O _3. It is preferable that

  Alternatively, the substrate protective layer is preferably a metal film, and in this case, the metal film is preferably mainly composed of at least one selected from the group consisting of Ti, Ta, Mo, and alloys thereof. .

  Here, the “main component” of the insulating film or metal film means a component having a content of 75% by mass or more.

  Moreover, it is preferable that the stress relaxation layer which has as a main component the same material as the main component of a substrate protective layer is provided in the surface on the opposite side to the side provided with the substrate protective layer.

  Furthermore, the method for manufacturing a photoelectric conversion element according to the present invention includes a laminated structure of a lower electrode, a photoelectric conversion layer, and an upper electrode on the surface opposite to the side provided with the substrate protective layer of the anodized substrate described above. It is characterized by forming.

  Here, the “main component” of the layer formed on the anodized substrate (lower electrode, photoelectric conversion layer, upper electrode, other optional layer provided as necessary) is a component having a content of 75% by mass or more. Means.

  The photoelectric conversion element according to the present invention is manufactured by the above-described method for manufacturing a photoelectric conversion element.

  In this case, the main component of the photoelectric conversion layer is preferably at least one compound semiconductor having a chalcopyrite structure, and the main component of the photoelectric conversion layer includes at least an Ib group element, a IIIb group element, and a VIb group element. One type of compound semiconductor is more preferable.

The main component of the photoelectric conversion layer is
At least one group Ib element selected from the group consisting of Cu and Ag;
At least one group IIIb element selected from the group consisting of Al, Ga and In;
It is preferably at least one compound semiconductor comprising at least one VIb group element selected from the group consisting of S, Se, and Te.

  The element group descriptions in this specification are based on the short-period periodic table. In the present specification, a compound semiconductor composed of a group Ib element, a group IIIb element, and a group VIb element is abbreviated as “I-III-VI group semiconductor”. Each of the Ib group element, the IIIb group element, and the VIb group element that are constituent elements of the I-III-VI group semiconductor may be one type or two or more types.

  Furthermore, the solar cell according to the present invention includes the above-described photoelectric conversion element.

  An anodized substrate for a photoelectric conversion element according to the present invention and a method for producing a photoelectric conversion element using the same are as follows: an anodized substrate in which an anodized film is formed on an Al base, the side on which a photoelectric conversion layer and the like are formed A substrate protective layer is provided on the surface on the opposite side. Therefore, in the manufacture of a photoelectric conversion element using this anodized substrate, the corrosion of the back surface of the anodized substrate due to the alkaline solution treatment by the CBD method or the like is suppressed, and the occurrence of cracks due to the corrosion of the back surface is prevented. It is possible to prevent the internal stress from being released and warping of the substrate. As a result, it is possible to prevent cracks and peeling from occurring in the photoelectric conversion layer, the lower electrode, and the like, and thus it is possible to manufacture a photoelectric conversion element and a solar cell having good photoelectric conversion characteristics.

  Moreover, the photoelectric conversion element and solar cell using the anodized film according to the present invention use a substrate protective layer having alkali resistance on the surface opposite to the side on which the photoelectric conversion layer or the like of the anodized substrate is formed. Manufactured. Therefore, in the manufacture of this photoelectric conversion element, it is possible to suppress the corrosion of the back surface of the anodized substrate due to the alkaline solution treatment by the CBD method or the like, and to prevent the occurrence of cracks due to the corrosion on the back surface. It becomes possible to obtain characteristics.

Schematic sectional view showing the structure of the anodized substrate according to the first embodiment Diagram showing the relationship between the number of cracks on the back of the anodized substrate and the curvature of the substrate Schematic sectional view showing the structure of the anodized substrate according to the second embodiment Schematic cross-sectional view in the short-side direction of the photoelectric conversion element according to the first embodiment 1 is a schematic sectional view in a longitudinal direction of a photoelectric conversion element according to a first embodiment. Diagram showing the relationship between the lattice constant and band gap of I-III-VI compound semiconductors Schematic cross-sectional view in the short direction of the photoelectric conversion element according to the second embodiment Schematic cross-sectional view in the longitudinal direction of the photoelectric conversion element according to the second embodiment Microscopic image showing the back side of the anodized substrate in the example Microscopic image showing the back side of the anodized substrate in the comparative example Schematic cross-sectional view showing the general structure of a CIS or CIGS solar cell using an anodized substrate

  Hereinafter, although an embodiment of the present invention is described using a drawing, the present invention is not limited to this. In addition, in order to make it easy to visually recognize, the scale of each component in the drawing is appropriately changed from the actual one.

“First Embodiment of Anodized Substrate”
The structure of the anodized substrate according to the first embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view of an anodized substrate according to this embodiment. The anodized substrate 10a is a substrate for forming a semiconductor circuit on the anodized film 12 as an insulating layer.

  An anodized substrate 10a shown in FIG. 1 anodizes both surfaces of an Al base 11 and forms a substrate protective layer 13 having alkali resistance on one of the anodized films formed on both surfaces. Is formed. That is, the anodized substrate 10a is composed of an anodized film 12 formed on both surfaces by anodization, an Al base 11 that has not been anodized, and a substrate protective layer 13 formed on one of the anodized films 12. Become. In this case, the anodized substrate 10a has a four-layer structure of substrate protective layer 13 / anodized film 12 / Al base material 11 / anodized film 12.

(Al base material and anodizing)
The Al base 11 may be Japanese Industrial Standard (JIS) 1000 series pure Al, Al-Mn based alloy, Al-Mg based alloy, Al-Mn-Mg based alloy, Al-Zr based alloy, Al-- An alloy of Al and other metal elements such as an Si-based alloy and an Al—Mg—Si-based alloy may be used (see “Aluminum Handbook 4th Edition” (1990, published by Light Metal Association)).

  The thickness of the Al base material 11 before anodization is not particularly limited. The thickness of the Al base material 11 before anodization can be appropriately selected from the mechanical strength of the anodized substrate 10a, the reduction in thickness and weight, and the stress calculation results of material characteristics. 1 to 0.3 mm is more preferable. Note that when the anodized substrate 10a is manufactured, the thickness of the Al material 11 is reduced by anodic oxidation, pre-cleaning and polishing of the anodic oxidation, and it is necessary to make the thickness in anticipation of it.

Anodization can be performed by immersing the Al base 11 as an anode in an electrolyte together with a cathode and applying a voltage between the anode and the cathode. If necessary, the surface of the Al material 11 is subjected to a cleaning process, a polishing smoothing process, and the like. Carbon, Al, or the like is used as the cathode. The electrolyte is not limited, and an acidic electrolytic solution containing one or more acids such as sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, and amidosulfonic acid is preferably used. The anodizing conditions are not particularly limited by the type of electrolyte used. As conditions, for example, an electrolyte concentration of 1 to 80% by mass, a liquid temperature of 5 to 70 ° C., a current density of 0.005 to 0.60 A / cm ² , a voltage of 1 to 200 V, and an electrolysis time of 3 to 500 minutes are appropriate. It is. As the acidic electrolyte, sulfuric acid, phosphoric acid, oxalic acid, or a mixture thereof is preferable. In the case of using such an acidic electrolytic solution, an electrolyte concentration of 4 to 30% by mass, a liquid temperature of 10 to 30 ° C., a current density of 0.002 to 0.30 A / cm ² , and a voltage of 20 to 100 V are preferable.

  The thickness of the anodic oxide film 12 is not particularly limited as long as it has an insulating property and a surface hardness that prevents damage due to mechanical shock during handling. However, if it is too thick, there is a problem in terms of flexibility. There is a case. From this, the preferred thickness is 0.1 to 100 μm, and the thickness can be controlled by the electrolysis time together with constant current electrolysis and constant voltage electrolysis.

  In order to suppress warping of the anodized substrate due to the difference in thermal expansion coefficient between Al and the anodic oxide film, and film peeling due to this in the process of manufacturing the photoelectric conversion element, as shown in FIG. It is preferable that the anodic oxide film 12 is formed on both sides of the film. When the anodic oxide film 12 is formed on both sides of the anodized substrate 10a, the film thicknesses of the two anodic oxide films 12 are made substantially equal in consideration of the balance of thermal stresses on both sides of the substrate, or a photoelectric conversion layer is formed. It is preferable that the anodic oxide film 12 on the non-surface side is slightly thicker than the other anodic oxide film 12.

  When the Al base 11 is anodized, an oxidation reaction proceeds in a substantially vertical direction from the surface, and an anodized film 12 is generated. When the above-described acidic electrolytic solution is used, the anodic oxide film 12 has a large number of fine hexagonal columnar bodies having a substantially regular hexagonal shape in plan view arranged without gaps, and there is a fine hole in the center of each fine columnar body, and the bottom surface is It becomes a rounded shape. A barrier layer (usually a thickness of 0.02 to 0.1 μm) is formed on the bottom of the fine columnar body. In addition, unlike an acidic electrolytic solution, by carrying out an electrolytic treatment with a neutral electrolytic solution such as boric acid, a dense anodic oxide film can be obtained instead of an anodic oxide film in which porous fine columnar bodies are arranged. For the purpose of increasing the thickness of the barrier layer, it is also possible to use a pore filling method in which a porous anodic oxide film 12 is formed with an acidic electrolyte and then re-electrolyzed with a neutral electrolyte.

(Substrate protective layer)
The substrate protective layer 13 is a layer having alkali resistance against an alkaline solution. Here, in the above-mentioned definition of “alkali resistance”, the pH is 11. However, the pH when actually performing the CBD method or the like is not limited to pH 11. It is preferable that the thermal expansion coefficient of the main component of the substrate protective layer 13 is substantially equal to the thermal expansion coefficient of Al ₂ O ₃ . Thereby, the curvature etc. of the anodic oxidation substrate 10a by the difference in thermal expansion coefficient of the board | substrate protective layer 13 and the anodic oxide film 12 can be reduced.

The substrate protective layer 13 is preferably an insulating film, and the material thereof is not particularly limited, and SiO ₂ , TiO ₂ , TiN, Al ₂ O ₃ and soda lime glass (SLG) can be used. Here, Al ₂ O ₃ exemplified above refers to a film formed by a solid phase method such as a sputtering method. In this case, the, Al 2 _O 3, based on which is formed by anodic oxidation _(anodic oxide film) for the nature of the membrane are different, can be used as Al ₂ O ₃ if the substrate protective layer 13 illustrated above. Or it is preferable that the board | substrate protective layer 13 is a metal film, It does not restrict | limit especially as the material, Ti, Ta, Mo, etc. can be used.

  Moreover, it does not restrict | limit especially as a formation method of the board | substrate protective layer 13, A vacuum evaporation method, CVD (Chemical Vapor Deposition) method, sputtering method, etc. can be used.

  The film thickness of the substrate protective layer 13 can be appropriately set depending on the alkaline solution used in the CBD method, the processing time of the CBD method, etc., the resistance of the material of the substrate protective layer 13 to the alkaline solution, and the like. When the material of the protective layer 13 is SLG, 20 to 500 nm is preferable, and 50 to 200 nm is more preferable.

  By providing the substrate protective layer 13 on one surface of the anodized substrate 10a, the surface provided with the substrate protective layer 13 can be prevented from being corroded by the alkaline solution, and the generation of cracks in the anodized substrate 10a can be prevented. Warpage of the oxide substrate 10a can be prevented. FIG. 2 is a diagram showing the relationship between the number of cracks on the back surface of the anodized substrate without the substrate protective layer and the curvature of the substrate obtained by the present inventors. In this figure, the number of cracks is the number of cracks that can be visually confirmed when the anodized substrate is immersed in an alkaline solution. Thus, it can be seen that the curvature of the substrate tends to decrease as the number of cracks on the back surface decreases. This suggests that cracking and peeling can be prevented from occurring in the photoelectric conversion layer, the lower electrode and the like by suppressing the corrosion on the back surface.

  As described above, the anodized substrate for the photoelectric conversion element of this embodiment according to the present invention is the opposite of the side on which the anodized substrate having the anodized film formed on the Al base is formed. It is comprised so that a board | substrate protective layer may be provided in the side surface. Therefore, in the manufacture of a photoelectric conversion element using this anodized substrate, the corrosion of the back surface of the anodized substrate due to the alkaline solution treatment by the CBD method or the like is suppressed, and the occurrence of cracks due to the corrosion of the back surface is prevented. It is possible to prevent the internal stress from being released and warping of the substrate. As a result, it is possible to prevent the photoelectric conversion layer, the lower electrode, and the like from being cracked or peeled off, so that a photoelectric conversion element having good photoelectric conversion characteristics can be manufactured.

  Furthermore, in the anodized substrate for the photoelectric conversion element of the present embodiment, the flatness of the anodized substrate is increased by the effects described above, and the temperature uniformity of the substrate temperature in the film forming process after the CdS buffer layer is formed. And in-plane uniformity of film characteristics such as film thickness and composition can be improved. As a result, the photoelectric conversion efficiency of the photoelectric conversion element can be improved. Moreover, since the influence of the warp of the anodized substrate can be reduced in the laminating step performed when manufacturing the solar cell, the yield of manufacturing the solar cell can be improved.

“Second Embodiment of Anodized Substrate”
Next, the structure of the anodized substrate according to the second embodiment of the present invention will be described. FIG. 3 is a schematic cross-sectional view of the anodized substrate 10c according to this embodiment. The anodized substrate 10c is a stress relaxation mainly composed of the same material as the main component of the substrate protective layer 13 on the anodized film 12 on the opposite side of the anodized substrate 10a on which the substrate protective layer 13 is formed. The configuration includes the layer 14. Therefore, the details of the other constituent elements are the same as those of the anodized substrate 10a, and thus are omitted unless particularly necessary.

(Stress relaxation layer)
The stress relaxation layer 14 is for balancing the stress of the anodized substrate provided with the alkali-resistant substrate protective layer 13 on the back surface. In other words, the warpage of the substrate due to the difference in thermal expansion coefficient between the Al base 11 or the anodic oxide film 12 and the substrate protective layer 13 is suppressed. The stress relaxation layer 14 is preferably an insulating film like the substrate protective layer 13, and the material thereof is not particularly limited, and includes SiO ₂ , TiO ₂ , TiN, Al ₂ O _3, soda lime glass (SLG), and the like. Can be used. Here, Al ₂ O ₃ exemplified above refers to a film formed by a solid phase method such as a sputtering method. In this case, the, Al 2 _O 3, based on which is formed by anodic oxidation _(anodic oxide film) for the nature of the membrane are different, can be used as Al ₂ O ₃ if the stress relaxation layer 14 illustrated above. Or it is preferable that the stress relaxation layer 14 is a metal film similarly to the board | substrate protective layer 13, and it does not restrict | limit especially as the material, Ti, Ta, Mo, etc. can be used.

  The stress relaxation layer 14 is preferably composed mainly of the same material as the main component of the substrate protective layer 13 because stress calculation is easy. Further, the film thickness of the stress relaxation layer 14 is made substantially equal to the film thickness of the substrate protective layer 13 in consideration of the balance of thermal stresses on both surfaces of the anodized substrate 10c, or the photoelectric conversion layer or the like is on the stress relaxation layer 14. In consideration of the formation, it is preferable that the substrate protection layer 13 be slightly thinner.

  When the stress relaxation layer 14 is a metal film, it is necessary to pattern the stress relaxation layer 14 in order to prevent conduction between cells. This patterning is not particularly limited as long as the resistance between the cells is 1000Ω or more, but is preferably performed by scribing simultaneously with the lower electrode 20. Moreover, it does not restrict | limit especially as a formation method of the stress relaxation layer 14, A vacuum evaporation method, CVD method, sputtering method, etc. can be used.

  As described above, the anodized substrate for the photoelectric conversion element of the present embodiment according to the present invention is also opposite to the side on which the anodized substrate having the anodized film formed on the Al base is formed. It is comprised so that a board | substrate protective layer may be provided in the side surface. Therefore, in the manufacture of the photoelectric conversion element using this anodized substrate, corrosion of the back surface of the anodized substrate due to the alkaline solution treatment by the CBD method or the like can be suppressed, and thus the same effect as that of the first embodiment can be obtained. Obtainable.

  Furthermore, in the anodized substrate for the photoelectric conversion element of the present embodiment, the stress balance of the entire anodized substrate is further maintained due to the presence of the stress relaxation layer, so that the flatness of the anodized substrate can be further improved. As a result, the photoelectric conversion efficiency of the photoelectric conversion element can be further improved. Moreover, since the influence of the warp of the anodized substrate can be reduced in the laminating step performed when manufacturing the solar cell, the yield of manufacturing the solar cell can be further improved.

`` Photoelectric conversion element manufacturing method, photoelectric conversion element and solar cell first embodiment ''
Next, the manufacturing method and structure of the photoelectric conversion element according to the first embodiment of the present invention will be described. 4A is a schematic cross-sectional view in the short direction of the photoelectric conversion element, and FIG. 4B is a schematic cross-sectional view in the longitudinal direction of the photoelectric conversion element.

  The manufacturing method of the photoelectric conversion element 1 according to this embodiment includes the lower electrode (back electrode) 20, the photoelectric conversion layer 30, and the buffer layer 40 on the anodized substrate 10 a described in the first embodiment of the anodized substrate. The upper electrode (transparent electrode) 50 is sequentially laminated. The laminated structure such as the photoelectric conversion layer 30 and the electrodes is formed on the surface of the anodized substrate 10a opposite to the side on which the substrate protective layer 13 is formed.

  Moreover, the manufacturing method of the photoelectric conversion element 1 includes a first groove 61 that penetrates only the lower electrode 20 and a second groove that penetrates the photoelectric conversion layer 30 and the buffer layer 40 in a cross-sectional view in the short direction. And a fourth groove portion 63 that penetrates only the photoelectric conversion layer 30, the buffer layer 40, and the upper electrode 50 in a longitudinal sectional view. 64 is formed.

  With the above configuration, a structure in which the element is separated into a large number of cells C by the first to fourth groove portions 61 to 64 is obtained. Further, by filling the second groove 62 with the upper electrode 50, a structure in which the upper electrode 50 of a certain cell C is connected in series to the lower electrode 20 of the adjacent cell C is obtained.

(Anodized substrate)
The substrate of the photoelectric conversion element 1 according to the present embodiment is the anodized substrate 10a described in the first embodiment of the anodized substrate, as shown in FIGS. 4A and 4B.

(Photoelectric conversion layer)
The photoelectric conversion layer 30 is a layer that generates current by light absorption. The main component is not particularly limited, and is preferably at least one compound semiconductor having a chalcopyrite structure. Further, the main component of the photoelectric conversion layer 30 is preferably at least one compound semiconductor composed of an Ib group element, an IIIb group element, and a VIb group element.

Furthermore, since the light absorption rate is high and high photoelectric conversion efficiency is obtained,
The main component of the photoelectric conversion layer 30 is:
At least one group Ib element selected from the group consisting of Cu and Ag;
At least one group IIIb element selected from the group consisting of Al, Ga and In;
It is preferably at least one compound semiconductor comprising at least one VIb group element selected from the group consisting of S, Se, and Te.

As the compound semiconductor,
CuAlS ₂ , CuGaS ₂ , CuInS ₂ ,
CuAlSe ₂ , CuGaSe ₂ , CuInSe ₂ (CIS),
AgAlS ₂ , AgGaS ₂ , AgInS ₂ ,
AgAlSe ₂ , AgGaSe ₂ , AgInSe ₂ ,
AgAlTe ₂ , AgGaTe ₂ , AgInTe ₂ ,
_{Cu (In 1-x Ga x} ) Se 2 (CIGS), Cu (In 1-x Al x) Se 2, Cu (In 1-x Ga x) (S, Se) 2,
_{Ag (In 1-x Ga x} ) Se 2, and _{Ag (In 1-x Ga x} ) (S, Se) 2 , and the like.

The photoelectric conversion layer 30 particularly preferably includes CuInSe ₂ (CIS) and / or Cu (In, Ga) Se ₂ (CIGS) in which Ga is dissolved. CIS and CIGS are semiconductors having a chalcopyrite crystal structure, have high light absorption, and high photoelectric conversion efficiency has been reported. Moreover, there is little degradation of efficiency by light irradiation etc. and it is excellent in durability.

  The photoelectric conversion layer 30 contains impurities for obtaining a desired semiconductor conductivity type. Impurities can be contained in the photoelectric conversion layer 30 by diffusion from adjacent layers and / or active doping. The photoelectric conversion layer 30 may include one or more semiconductors other than the I-III-VI group semiconductor. As a semiconductor other than the I-III-VI group semiconductor, a semiconductor composed of a group IVb element such as Si (group IV semiconductor), a semiconductor composed of a group IIIb element such as GaAs and a group Vb element (group III-V semiconductor), and Examples thereof include semiconductors (II-VI group semiconductors) composed of IIb group elements such as CdTe and VIb group elements. Content in particular of the I-III-VI group semiconductor in the photoelectric converting layer 30 is not restrict | limited, 75 mass% or more is preferable, 95 mass% or more is more preferable, 99 mass% or more is especially preferable.

  CIGS layer deposition methods include 1) Multi-source co-evaporation (JRTuttle et.al, Mat.Res.Soc.Symp.Proc., Vol.426 (1996) p.143. And H.Miyazaki, et. al, phys.stat.sol. (a), Vol.203 (2006) p.2603., etc.), 2) Selenization (T.Nakada et.al ,, Solar Energy Materials and Solar Cells 35 (1994) 204-214. And T. Nakada et.al ,, Proc. Of 10th European Photovoltaic Solar Energy Conference (1991) 887-890.) 3) Sputtering (JHErmer, et.al, Proc. 18th IEEE Photovoltaic Specialists Conf. (1985) 1655-1658. And T. Nakada, et.al, Jpn. J. Appl. Phys. 32 (1993) L1169-L1172., Etc.) 4) Hybrid sputtering method (T. Nakada, et.al) , Jpn.Appl.Phys.34 (1995) 4715-4721. Etc.), and 5) Mechanochemical process method (T.Wada et.al, Phys.stat.sol. (A), Vol.203 (2006) p2593 etc.) are known. Other CIGS film formation methods include screen printing, proximity sublimation, MOCVD, and spraying. For example, a fine particle film containing an Ib group element, an IIIb group element, and a VIb group element is formed on a substrate by a screen printing method or a spray method, and a thermal decomposition process (in this case, a thermal decomposition process in an VIb group element atmosphere). For example, Japanese Patent Application Laid-Open No. 9-74065 and Japanese Patent Application Laid-Open No. 9-74213).

FIG. 5 is a diagram showing the relationship between the lattice constant and the band gap in main I-III-VI compound semiconductors. Various forbidden band widths (band gaps) can be obtained by changing the composition ratio. When a photon having energy larger than the band gap is incident on the semiconductor, the energy exceeding the band gap becomes a heat loss. It has been found by theoretical calculation that the conversion efficiency is maximized by the combination of the spectrum of sunlight and the band gap at about 1.4 to 1.5 eV. In order to increase the photoelectric conversion efficiency, for example, the Ga concentration of Cu (In, Ga) Se ₂ (CIGS) is increased, the Al concentration of Cu (In, Al) Se ₂ is increased, or Cu (In, Ga) (S , Se) By increasing the S concentration of ₂ or increasing the band gap, a band gap with high conversion efficiency can be obtained. In the case of CIGS, it can be adjusted in the range of 1.04 to 1.68 eV.

(Electrode and buffer layer)
The lower electrode (back electrode) 20 and the upper electrode (transparent electrode) 50 are both made of a conductive material. The upper electrode 50 on the light incident side needs to have translucency.

For example, Mo can be used as the material of the lower electrode 20. The thickness of the lower electrode 20 is preferably 100 nm or more, and more preferably 0.45 to 1.0 μm. The film formation method of the lower electrode 20 is not particularly limited, and examples thereof include vapor phase film formation methods such as an electron beam evaporation method and a sputtering method. As the main component of the upper electrode 50, ZnO, ITO (indium tin oxide), SnO ₂ , and combinations thereof are preferable. The upper electrode 50 may have a single layer structure or a laminated structure such as a two-layer structure. The thickness of the upper electrode 50 is not particularly limited, and is preferably 0.3 to 1 μm.

  The buffer layer 40 is preferably CdS, ZnS, ZnO, ZnMgO, ZnS (O, OH), or a combination thereof. The thickness of the buffer layer is not particularly limited and is preferably 0.05 to 0.2 μm. The buffer layer 40 can be formed using a sputtering method, a CBD method, or the like, but it is preferable to use the CBD method because there are few steps.

  A preferable combination of the compositions of the lower electrode 20 / photoelectric conversion layer 30 / buffer layer 40 / upper electrode 50 includes, for example, Mo lower electrode / CIGS photoelectric conversion layer / CdS buffer layer / ZnO upper electrode.

(Other layers)
The photoelectric conversion element 1 can be provided with arbitrary layers other than what was demonstrated above as needed. For example, between the anodized substrate 10a and the lower electrode 20 and / or between the lower electrode 20 and the photoelectric conversion layer 30, an adhesion layer (buffer layer) for enhancing the adhesion between the layers as necessary. Can be provided.

  Moreover, the photoelectric conversion element 1 can be preferably used for a solar cell or the like. If necessary, a cover glass, a protective film, or the like can be attached to the photoelectric conversion element 1 to form a solar cell.

  As described above, in the method for manufacturing a photoelectric conversion element according to the present invention, in the anodized substrate in which the anodized film is formed on the Al base, the substrate is protected on the surface opposite to the side on which the photoelectric conversion layer or the like is formed. An anodized substrate 10a having a layer is used. Therefore, in the manufacture of a photoelectric conversion element using this anodized substrate, the corrosion of the back surface of the anodized substrate due to the alkaline solution treatment by the CBD method or the like is suppressed, and the occurrence of cracks due to the corrosion of the back surface is prevented. It is possible to prevent the internal stress from being released and warping of the substrate. As a result, it is possible to prevent the photoelectric conversion layer, the lower electrode, and the like from being cracked or peeled off, so that a photoelectric conversion element having good photoelectric conversion characteristics can be manufactured.

  Moreover, the photoelectric conversion element and solar cell which concern on this invention use the anodized substrate 10a provided with the board | substrate protective layer 13 which has alkali resistance in the surface on the opposite side to the side in which a photoelectric converting layer etc. are formed. Therefore, in the manufacture of this photoelectric conversion element, the corrosion of the back surface of the anodized substrate due to the alkaline solution treatment by the CBD method or the like is suppressed, the occurrence of cracks due to the corrosion of the back surface is prevented, and the internal stress on the back surface side is released. Thus, warping of the substrate can be prevented. As a result, since it is possible to prevent cracks and peeling from occurring in the photoelectric conversion layer, the lower electrode, and the like, it is possible to obtain good photoelectric conversion characteristics.

  Furthermore, in the photoelectric conversion element of this embodiment, the flatness of the anodized substrate is increased by the effects described above, and the temperature uniformity of the substrate temperature is improved in the film formation process after the film formation of the CdS buffer layer. In-plane uniformity of film characteristics such as film thickness can be improved. As a result, the photoelectric conversion efficiency of the photoelectric conversion element can be improved. Moreover, since the influence of the warp of the anodized substrate can be reduced in the laminating step performed when manufacturing the solar cell, the yield of manufacturing the solar cell can be improved.

“Second Embodiment of Photoelectric Conversion Element Manufacturing Method, Photoelectric Conversion Element, and Solar Cell”
Next, the manufacturing method of the photoelectric conversion element of 2nd Embodiment which concerns on this invention, and its structure are demonstrated. 6A is a schematic cross-sectional view in the short direction of the photoelectric conversion element, and FIG. 6B is a schematic cross-sectional view in the longitudinal direction of the photoelectric conversion element.

  The manufacturing method of the photoelectric conversion element 2 according to the present embodiment is different from the first embodiment in that the anodized substrate 10c including the stress relaxation layer 14 described above is used. Therefore, detailed description of other components similar to those in the first embodiment is omitted unless there is a particular problem. In addition, the same components as those in the first embodiment are denoted by the same reference numerals.

  The manufacturing method of the photoelectric conversion element 2 includes a lower electrode (back electrode) 20, a photoelectric conversion layer 30, a buffer layer 40, and an upper electrode (transparent electrode) on the anodized substrate 10c described in the second embodiment of the anodized substrate. ) 50 in order. Also in this embodiment, the laminated structure such as the photoelectric conversion layer 30 and the electrodes is formed on the surface of the anodized substrate 10c opposite to the side on which the substrate protective layer 13 is formed.

  As described above, when the stress relaxation layer 14 is a metal film, it is necessary to pattern the stress relaxation layer in order to prevent conduction between cells. This patterning is not particularly limited as long as the resistance between the cells is 1000Ω or more, but is preferably performed by scribing simultaneously with the lower electrode 20.

  Moreover, the photoelectric conversion element 2 can also be preferably used for a solar cell or the like. If necessary, a cover glass, a protective film, or the like can be attached to the photoelectric conversion element 2 to form a solar cell.

  As described above, in the method for manufacturing a photoelectric conversion element according to the present invention, in the anodized substrate in which the anodized film is formed on the Al base, the substrate is protected on the surface opposite to the side on which the photoelectric conversion layer is formed. An anodized substrate 10c having a layer is used. Therefore, in the production of this photoelectric conversion element, corrosion of the back surface of the anodized substrate due to the alkaline solution treatment by the CBD method or the like can be suppressed. As a result, the same effects as those of the first embodiment can be obtained for the method of manufacturing the photoelectric conversion element.

  Moreover, the photoelectric conversion element and solar cell which concern on this invention are using the anodized board | substrate 10c provided with the board | substrate protective layer 13 which has alkali resistance in the surface on the opposite side to the side in which a photoelectric converting layer etc. are formed. Therefore, in the production of this photoelectric conversion element, corrosion of the back surface of the anodized substrate due to the alkaline solution treatment by the CBD method or the like can be suppressed. Thus, the same effects as those of the first embodiment can be obtained for the photoelectric conversion element and the solar cell.

  Furthermore, in the method for manufacturing a photoelectric conversion element, the photoelectric conversion element, and the solar cell of this embodiment, the stress balance of the anodized substrate is further maintained by the presence of the stress relaxation layer, and thus the flatness of the anodized substrate is further improved. be able to. As a result, the photoelectric conversion efficiency of the photoelectric conversion element can be further improved. Moreover, since the influence of the warp of the anodized substrate can be reduced in the laminating step performed when manufacturing the solar cell, the yield of manufacturing the solar cell can be further improved.

  Examples of the photoelectric conversion element according to the present invention will be described.

(Example)
Using an Al alloy XL material (thickness: 300 μm) as a base material, an anodized film (thickness: 10 μm) under anodizing conditions in which a voltage of 40 V is applied using a DC power source in a 0.5 M oxalic acid aqueous solution at 16 ° C. ) Was formed on both sides of the Al base material to form an anodized substrate. The anodized substrate was washed with water and dried.

  Thereafter, SLG having a film thickness of 200 nm was formed on both surfaces of the anodized substrate by sputtering to form a substrate protective layer and a stress relaxation layer.

  Next, a Mo electrode (thickness: 0.8 μm) was formed as a lower electrode on the anodized film of the anodized substrate by sputtering with a size of 3 cm × 3 cm.

And the CIGS photoelectric converting layer was formed into a film by sputtering method on this Mo electrode. In this example, a high purity copper disk-shaped target and a high purity indium (purity 99.9999%), high purity Ga (purity 99.999%) and high purity Se (purity 99.999%) disk. A shaped target was used. A chromel-alumel thermocouple was used as the substrate temperature monitor. The film formation method of the CIGS photoelectric conversion layer is as follows. First, the main vacuum chamber was evacuated to 10 ⁻⁶ Torr, high purity argon gas (99.999%) was introduced into the sputtering chamber, and the variable leak valve was adjusted to 3 × 10 ⁻² Torr. Next, a CIGS thin film was formed. Film forming conditions were performed at a maximum substrate temperature of 520 ° C. by controlling a deposition rate from each evaporation source. The thickness of the manufactured CIGS film was about 2 μm.

  Next, a CdS buffer layer (thickness: about 90 nm) was deposited as a buffer layer by the CBD method. The treatment conditions of the CBD method at this time were PH11 (ammonia aqueous solution), liquid temperature of 80 ° C., and immersion time of 15 minutes.

(Comparative example)
The process which forms the board | substrate protective layer and the stress relaxation layer was not performed, but the process similar to the said Example was implemented except that.

(Evaluation)
About each anodized board | substrate of an Example and a comparative example, the back surface after a CdS buffer layer formation process was observed with the microscope.

(result)
7 and 8 are microscopic images of the back surface of the anodized substrates of Examples and Comparative Examples, respectively. As a result, it was found that cracks did not occur on the back surface of the substrate in the process of the example, and cracks occurred on the back surface of the substrate in the process of the comparative example.

DESCRIPTION OF SYMBOLS 1, 2 Photoelectric conversion element 10 Anodized substrate 11 Al base material 12 Anodized film 13 Substrate protective layer 14 Stress relaxation layer 20 Lower electrode 30 Photoelectric conversion layer 40 Buffer layer 50 Upper electrode

Claims (13)

In an anodized substrate in which an anodized film is formed on both sides of an Al base material,
An anodized substrate comprising a substrate protective layer having alkali resistance on one of the anodized films. _2. The anodized substrate according to claim 1, wherein a thermal expansion coefficient of a main component of the substrate protective layer is substantially equal to a thermal expansion coefficient of Al ₂ O ₃ .   The anodized substrate according to claim 1, wherein the substrate protective layer is an insulating film. Wherein the insulating film is, soda lime _glass, according to claim 3, characterized in that at least one member selected from the group consisting of SiO _2, TiO 2, TiN and _Al 2 _{O 3} as a main component Anodized substrate.   The anodized substrate according to claim 1, wherein the substrate protective layer is a metal film.   6. The anodized substrate according to claim 5, wherein the metal film is mainly composed of at least one selected from the group consisting of Ti, Ta, Mo and alloys thereof.   7. A stress relieving layer comprising as a main component the same material as the main component of the substrate protective layer is provided on the surface opposite to the side provided with the substrate protective layer. The anodized substrate according to any one of the above.   A laminated structure of a lower electrode, a photoelectric conversion layer, and an upper electrode is formed on a surface of the anodized substrate according to any one of claims 1 to 7 opposite to the side provided with the substrate protective layer. A method for producing a photoelectric conversion element.   A photoelectric conversion element manufactured by the method for manufacturing a photoelectric conversion element according to claim 8.   The photoelectric conversion element according to claim 9, wherein a main component of the photoelectric conversion layer is at least one compound semiconductor having a chalcopyrite structure.   11. The photoelectric conversion element according to claim 10, wherein a main component of the photoelectric conversion layer is at least one compound semiconductor composed of a group Ib element, a group IIIb element, and a group VIb element. The main component of the photoelectric conversion layer is
At least one group Ib element selected from the group consisting of Cu and Ag;
At least one group IIIb element selected from the group consisting of Al, Ga and In;
The photoelectric conversion element according to claim 11, wherein the photoelectric conversion element is at least one compound semiconductor composed of at least one VIb group element selected from the group consisting of S, Se, and Te.   A solar cell comprising the photoelectric conversion element according to claim 9.