JP2010027662A - Power generation body and method of manufacturing power generation body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power generation body using a chalcopyrite-type compound semiconductor thin film having a super straight-type structure, and to provide a method of manufacturing the power generation body. <P>SOLUTION: This CIS-based compound semiconductor thin film power generation body having a super straight-type structure is formed by a method including: forming a comb metal electrode 2 on a substrate 1 composed of a light transmittable material; remaining a part of the formed comb metal electrode 2 as an electrode retrieving part 21; and laminating a transparent conductive layer 3, a buffer layer 4, a light absorbing layer 5 composed of a chalcopyrite-type compound semiconductor thin film containing Cu, In and Se, and a rear surface electrode layer 6 in this order by a sputtering method while covering parts other than the electrode retrieving part 21. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power generator and the like, and more particularly to a power generator having a light absorption layer including a chalcopyrite type compound semiconductor.

In recent years, interest in the environment has increased worldwide, such as prevention of global warming and reduction of waste. In particular, power generation is attracting attention because it can cause various pollutions such as air and water quality while consuming a large amount of resources. Especially, solar power generation is inexhaustible and does not produce any harmful emissions. There are great expectations.
This solar power generation has been developed by various companies so far, and some of them have already been put into practical use. Among them, a CIS compound semiconductor thin film solar cell using a chalcopyrite type compound semiconductor thin film centering on Cu—In—Se as a light absorption layer (see Patent Document 1) has high photoelectric conversion efficiency and excellent long-term stability. It is attracting attention because of its relatively low cost, and each company has begun commercialization.

JP 2006-49768 A

  In general, photovoltaic power generators typified by thin-film solar cells are classified into two types according to the incident direction of light serving as a power generation source. One is a structure that allows light to pass through the substrate made of a light-transmitting material (super straight type), and the other is that light is incident from the side of each layer laminated on the substrate and light is transmitted to the substrate. It is known that the structure does not transmit light (substrate type).

  In the case of a photovoltaic power generation using the CIS compound semiconductor thin film described above, a substrate type structure such as glass substrate / back electrode layer / Cu—In—Se light absorption layer / buffer layer / transparent conductive layer is usually adopted. A higher conversion efficiency is obtained. In particular, it is known that growing a cadmium sulfide (CdS) layer as a buffer layer by a solution growth method on a Cu—In—Se light absorption layer is necessary to obtain a thin film power generator with high conversion efficiency. Yes.

  By the way, in the case of the substrate type, it is necessary to cover the surface with a transparent protective plate such as tempered glass that protects the surface of the power generation body from falling objects such as rain, snow, and hail. On the other hand, in the case of the super straight type, the substrate to be used can be used as a protective plate for protecting the surface of the power generation body from falling objects, and the material can be simplified. For this reason, simplification of the material used etc. can be anticipated by employ | adopting a superstrate type | mold structure for the electric power generation body which uses a CIS type compound semiconductor thin film. Further, in the case of the substrate type structure, there is a possibility of adversely affecting the underlying transparent conductive layer or the like when forming the metal electrode, but in the case of the super straight type structure, there is no such problem.

However, when a Cu—In—Se light absorption layer is laminated on a cadmium sulfide (CdS) layer as a buffer layer formed by a solution growth method in a superstrate type structure which is a reverse lamination structure as compared with the case of the substrate type structure. A large number of defects are generated in the Cu—In—Se light absorption layer, resulting in a problem that a thin film power generator with good conversion efficiency cannot be obtained. In addition, when the CdS layer is grown by the solution growth method, a large amount of solid CdS and alkaline waste liquid is generated, and thus there is a problem that waste disposal costs increase. For this reason, the present condition is that the CIS type compound semiconductor thin film power generation body which has a superstrate type structure is not obtained.
An object of the present invention is to provide a power generator using a chalcopyrite type compound semiconductor thin film having a super-straight structure and a method for manufacturing the power generator.

  According to the present invention, a power generation unit having a structure in which light is incident through a substrate, the electrode being formed from a light-transmitting material and receiving light, and an electrode that is formed on the substrate and can be connected to an external wiring A metal electrode provided with a portion, a transparent conductive layer formed on the substrate while covering a portion other than the electrode extraction portion of the metal electrode, a buffer layer formed on the transparent conductive layer, and a layer formed on the buffer layer. There is provided a power generator characterized by having at least a light absorption layer composed of a filmed chalcopyrite type compound semiconductor thin film and a back electrode layer formed on the light absorption layer.

Here, in the power generator to which the present invention is applied, the chalcopyrite type compound semiconductor thin film of the light absorption layer is made of a Cu—In—Se based semiconductor material containing copper (Cu), indium (In) and selenium (Se). Preferably, it is configured.
The buffer layer is preferably formed on the transparent conductive layer by a sputtering method. Furthermore, the metal electrode, the transparent conductive layer, the light absorption layer, and the back electrode layer are preferably laminated on the substrate by a sputtering method.

  In the power generator to which the present invention is applied, it is preferable that the electrode lead-out portion of the metal electrode is provided on the end surface of the substrate. Furthermore, it is preferable that the electrode extraction part of a metal electrode is provided in the light-incidence surface of a board | substrate.

  Next, according to the present invention, there is provided a method for producing a power generator having a super straight structure, wherein a metal electrode is formed on a substrate made of a light transmissive material, and the formed metal electrode. A thin conductive film, a buffer layer, a light absorption layer, and a back electrode layer are sequentially formed on the substrate by sputtering while leaving a part of the electrode as an electrode extraction part and covering the part other than the electrode extraction part of the metal electrode. And a light absorption layer comprising a chalcopyrite compound semiconductor thin film containing copper (Cu), indium (In) and selenium (Se). Provided.

  Here, in the method of manufacturing a power generator to which the present invention is applied, the electrode extraction part of the metal electrode covers the electrode extraction part with an adhesion mask, and then a transparent conductive layer, a buffer layer, and a light absorption layer on the metal electrode The back electrode layer is preferably laminated in order.

  The light absorption layer is formed by laminating a plurality of mixtures having different compositions containing at least Cu and In, or Cu and Se, or In and Se, and then melting and diffusing the mixtures with each other. Preferably it is formed.

According to the present invention, the power generation body using the chalcopyrite type compound semiconductor thin film has a super straight structure, so that the substrate required for the substrate structure can be reduced to one and the material can be simplified. It becomes.
Furthermore, unlike the substrate type structure, there is no possibility of adversely affecting other layers when forming the metal electrode.
Further, by providing an electrode lead-out portion that is not covered with another thin film layer such as a transparent conductive layer in a part of the metal electrode, connection to external wiring becomes possible.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. Further, the drawings to be used are for explaining the present embodiment and do not represent the actual size.

  FIG. 1 is a diagram illustrating a first embodiment of a power generator to which the present embodiment is applied. FIG. 1 shows a CIS compound semiconductor thin film power generator (power generator) 10 having a superstrate structure using a chalcopyrite type compound semiconductor. FIG. 1A is a diagram illustrating a planar structure, and FIG. 1B is a diagram illustrating a cross-sectional structure taken along line XY of FIG. 1A.

  As shown in FIGS. 1 (a) and 1 (b), the power generator 10 has a connection between a substrate 1 made of a light transmissive material and an external wiring (not shown) formed on the substrate 1. A comb-shaped metal electrode (metal electrode) 2 provided with a possible electrode lead-out portion 21; a transparent conductive layer 3 formed on the substrate 1 while covering a portion other than the electrode lead-out portion 21 of the comb-shaped metal electrode 2; A buffer layer 4 formed on the layer 3, a light absorption layer 5 formed of a chalcopyrite type compound semiconductor thin film formed on the buffer layer 4, and a back electrode formed on the light absorption layer 5 Layer 6. The power generation body 10 having a super straight type structure is a power generation body that generates power by making light transmitted through the substrate 1 incident on the light absorption layer 5.

  The substrate 1 is formed using a light transmissive material. Here, the light transmissive material is a material having a degree of transparency that allows light incident from the substrate 1 side to pass therethrough and irradiate the light absorption layer 5. For example, glass, a light transmissive polymer material, etc. are mentioned. By adopting a super straight structure as the structure of the CIS compound semiconductor thin film power generator, the substrate 1 becomes the foundation of each thin film laminated on the substrate 1, and the surface of the power generator 10 is covered with rain, snow, hail, etc. It can be used as a protective plate to protect against falling objects. For this reason, it is preferable that the board | substrate 1 has the intensity | strength which can protect the surface of the electric power generation body 10 from light transmittance and falling objects, such as rain, snow, and a hail.

Although the material which forms the comb-shaped metal electrode (metal electrode) 2 is not specifically limited, In this Embodiment, it forms by sputtering method using aluminum (Al). By making the shape of the metal electrode into a comb shape, electrons generated on the transparent conductive layer 3 can be collected efficiently. A voltage is generated between the light absorption layer 5 and an electrode (not shown) provided on the back electrode layer 6 by receiving light irradiation from the substrate 1 side.
As shown in FIG. 1A, the electrode lead-out portion 21 formed at the end of the comb-shaped metal electrode (metal electrode) 2 has another layer (transparent conductive layer) laminated on the comb-shaped metal electrode (metal electrode) 2. Layer 3, buffer layer 4, light absorption layer 5, and back electrode layer 6) are not covered and formed in an exposed state to the atmosphere. The electrode extraction part 21 is connected to external wiring (not shown), and the generated current is extracted to the outside.

  The transparent conductive layer 3 is made of zinc oxide (ZnO) (Al—Zn—O or the like) doped with ITO (In—Sn—O) or a group III element (Al or the like). Here, the material constituting the transparent conductive layer 3 is a material that transmits at least light that irradiates the light absorption layer 5.

The buffer layer 4 is provided to form an electrical connection between the transparent conductive layer 3 and the light absorption layer 5. Conventionally, the buffer layer 4 has a cadmium sulfide (CdS) layer formed by a solution growth method. In this embodiment, a thin film of zinc nitride (ZnS) is formed on the transparent conductive layer 3 by a sputtering method. It is formed by.
By forming the buffer layer 4 on the transparent conductive layer 3 by the sputtering method, the light absorption layer 5 can be further formed on the buffer layer 4 by the sputtering method, and good power generation characteristics can be obtained.

The light absorption layer 5 is composed of a polycrystalline compound semiconductor thin film having a chalcopyrite structure containing copper (Cu), indium (In) and selenium (Se), and the band gap is optimized so as to easily absorb sunlight. Has been. As a material having a chalcopyrite structure containing Cu, In and Se, for example, a CuInSe ₂ based semiconductor material can be cited.
In the present embodiment, the pn junction of the light absorption layer 5 is a homojunction existing in the light absorption layer 5 and is divided into an n-type semiconductor layer and a p-type semiconductor layer. Light incident from the substrate 1 is mainly absorbed by the light absorption layer 5, excites electrons in the depletion layer near the pn junction formation portion, and the generated electrons flow to the transparent conductive layer 3 side, while the generated holes are Electricity is generated by flowing toward the back electrode layer 6 side.

  In the present embodiment, the light absorption layer 5 is formed with a p-type semiconductor layer on the back electrode layer 6 side of the light absorption layer 5 with respect to the average composition of Cu, In, and Se elements present in the light absorption layer 5. Thus, the light absorption layer 5 is formed so as to have an elemental composition gradient in the film thickness direction so that the n-type semiconductor layer is formed on the transparent conductive layer 3 side.

  Although the material which forms the back surface electrode layer 6 is not specifically limited, In this Embodiment, it forms on the light absorption layer 5 by sputtering method using molybdenum (Mo).

  FIG. 2 is a diagram illustrating another position of the electrode extraction portion of the power generation body 10 to which this exemplary embodiment is applied. As shown in FIG. 2A, the electrode extraction portion 22 provided at the end portion of the comb-shaped metal electrode 2 may be formed so as to protrude from the end surface of the substrate 1. Further, as shown in FIG. 2B, the electrode lead-out portion 23 provided at the end of the comb-shaped metal electrode 2 forms a portion that protrudes from the end face of the substrate 1, and further this protrusion portion is the light incident surface of the substrate 1. It may be formed by folding back.

  FIG. 3 is a diagram illustrating a second embodiment of a power generator to which the present embodiment is applied. The same code | symbol is used about the structure similar to 1st Embodiment of the electric power generation body shown in FIG. 1, and the description is abbreviate | omitted. FIG. 3A is a diagram illustrating a planar structure, and FIG. 3B is a diagram illustrating a cross-sectional structure taken along line XY in FIG. 3A.

As shown in FIG. 3A and FIG. 3B, the power generator 20 having a super-straight structure has a substrate 11 made of a light-transmitting material, and an electrode extraction portion 21a formed on the substrate 11. The comb-shaped metal electrode (metal electrode) 2a and the transparent conductive layer 3, the buffer layer 4, the light absorption layer 5, and the back electrode layer formed on the substrate 11 while covering the portion other than the electrode lead-out portion 21a of the comb-shaped metal electrode 2a 6.
Here, in the present embodiment, the electrode extraction portion 21 a provided at the end portion of the comb-shaped metal electrode 2 a is formed so as to protrude from the end surface of the substrate 11.

As shown in FIG. 3B, the substrate 11 has a groove 12 for wiring the comb-shaped metal electrode 2 a, and the comb-shaped metal electrode 2 a is formed so as to be embedded in the groove 12 of the substrate 11. . As a result, the comb-shaped metal electrode 2a is prevented from projecting to the surface of the substrate 11, and the other four layers (transparent conductive layer 3, buffer layer 4, light absorbing layer 5, back electrode layer 6) are flattened on the substrate 11. Can be laminated in various shapes.
This is because, for example, in the power generator 10 shown as the first embodiment in FIG. 1, the area of the comb-shaped metal electrode 2 formed in a wiring pattern is usually formed on the comb-shaped metal electrode 2. It is narrower than the four layers (transparent conductive layer 3, buffer layer 4, light absorption layer 5, back electrode layer 6), thereby preventing a step in the thin film laminated structure.

FIG. 4 is a diagram for explaining a case where a step is generated in the thin film laminated structure laminated on the comb-shaped metal electrode. The same code | symbol is used about the structure similar to 1st Embodiment of the electric power generation body shown in FIG. 1, and the description is abbreviate | omitted.
As shown in FIG. 4A, the film thicknesses of the other four layers (transparent conductive layer 3, buffer layer 4, light absorbing layer 5, back electrode layer 6) formed on the comb-shaped metal electrode 2 are sufficient. When it does not have a thickness, or when the thickness of the comb-shaped metal electrode 2 is excessively large, a step is generated in the thin film laminated structure between a portion formed on the comb-shaped metal electrode 2 and other portions. Therefore, the thickness of each thin film at the place where the step is generated becomes excessively thin. Further, as shown in FIG. 4B, when the other four layers (transparent conductive layer 3, buffer layer 4, light absorbing layer 5, back electrode layer 6) are excessively thin, a step is generated. In this case, the thin film laminated structure may be cut.
Such a step is eliminated by providing the substrate 1 with a groove 12 for wiring the comb-shaped metal electrode 2a.

(Method for manufacturing power generator)
Next, a method for producing a CIS compound semiconductor thin film power generator having a super straight structure to which the present embodiment is applied will be described. Here, the method for manufacturing the power generation body 10 of the first embodiment shown in FIG. 1 will be described as an example.
In the present embodiment, a soda-lime glass plate having a side of 138 mm square and a thickness of 0.55 mm is used as the substrate 1. The comb-shaped metal electrode 2 uses aluminum (Al), the transparent conductive layer 3 uses zinc oxide (ZnO), the buffer layer 4 uses zinc nitride (ZnS), and the back electrode layer 6 uses molybdenum (Mo). Each is formed into a film.

First, Al is sputtered on the substrate 1 to form the comb-shaped metal electrode 2 (metal electrode forming step). In the present embodiment, the thickness of the comb-shaped metal electrode 2 is 500 nm. The comb-shaped metal electrode 2 is formed on the substrate 1 by a sputtering method or a paste printing method. In this embodiment, a sputtering method using an adhesion mask is employed as described later.
Here, the sputtering method is generally ionized by applying a DC high voltage between the substrate 1 and a target made of a material to be deposited while introducing an inert gas (mainly Ar gas) in a vacuum. This is known as a method of causing Ar to collide with a target and depositing the repelled target material on the substrate 1.

  FIG. 5 is a diagram illustrating a method for forming the comb-shaped metal electrode 2. As shown in FIG. 5A, the comb-shaped metal electrode 2 is formed by placing an adhesion mask 7 having an opening in the shape of the comb-shaped metal electrode 2 on the substrate 1 and sputtering Al in this state. . After sputtering Al, the comb-shaped metal electrode 2 having a predetermined thickness is formed only at the opening.

  Next, a transparent conductive layer 3, a buffer layer 4, a light absorption layer 5, and a back electrode layer 6 are sequentially formed on the substrate 1 by sputtering while covering the formed comb-shaped metal electrode 2 to form a thin film laminated structure. (Thin film forming step). Here, in the present embodiment, a part of the comb-shaped metal electrode 2 is formed as the electrode extraction portion 21 as described below.

  As shown in FIG. 5 (b), the electrode lead-out portion 21 of the comb-shaped metal electrode 2 is an adhesion mask having a quarter-circle shape at the end of the comb-shaped metal electrode 2 formed on the substrate 1. In this state, each thin film is formed by sputtering. After each thin film is formed by the sputtering method, a part of the comb-shaped metal electrode 2 is left as the electrode extraction part 21 and is formed in a state exposed to the atmosphere. By connecting the electrode extraction portion 21 and an external wiring (not shown), the generated current can be extracted to the outside.

In the present embodiment, each thin film is formed as follows. The transparent conductive layer 3 is formed as a ZnO film having a thickness of 800 nm on the substrate 1 by sputtering while covering a portion other than the electrode extraction portion 21 of the comb-shaped metal electrode 2.
The buffer layer 4 is formed as a ZnS film having a thickness of 100 nm on the formed transparent conductive layer 3 by a sputtering method.

  The light absorption layer 5 is formed by laminating a plurality of mixtures having different compositions containing at least Cu and In, or Cu and Se, or In and Se, and then melting and diffusing the mixtures with each other. Is done.

In this embodiment, CuSe ₂ / In / CuSe ₂ / In ₂ Se ₃ is sequentially sputtered on the formed buffer layer 4 so that the film thicknesses become 100 nm / 150 nm / 100 nm / 200 nm, respectively. A filmed four-layer laminate is formed.
Subsequently, as the back electrode layer 6, Mo is deposited to a thickness of 500 nm by a sputtering method.

  Next, the substrate 1 having a thin film laminated structure is heated in an oven at 400 ° C. for 30 minutes, and the four-layer laminate described above is melted and diffused to each other, thereby changing to a composite of Cu—In—Se single layer. Let As a result, a semiconductor pn junction is formed in the light absorption layer 5 and power generation is possible by absorbing light.

  Although the present embodiment has been described above, the layer configuration of the power generators 10 and 20 is not limited thereto, and a necessary layer may be added as necessary. Moreover, the material which comprises each layer is also suitably selected as needed. Furthermore, although the sputtering method has been exemplified as the film forming means for each thin film layer, it is not limited thereto, and for example, each method such as vapor deposition and plating can be appropriately employed.

It is a figure explaining 1st Embodiment of an electric power generation body. It is a figure explaining the other position of the electrode extraction part of an electric power generation body. It is a figure explaining 2nd Embodiment of an electric power generation body. It is a figure explaining the case where a level | step difference arises in the thin film laminated structure laminated | stacked on the comb-shaped metal electrode. It is a figure explaining the formation method of a comb-shaped metal electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 ... Board | substrate, 2, 2a ... Comb-shaped metal electrode, 3 ... Transparent conductive layer, 4 ... Buffer layer, 5 ... Light absorption layer, 6 ... Back surface electrode layer, 7, 8 ... Deposit mask, 12 ... Groove, 21 , 21a, 22, 23...

Claims (9)

A power generator having a structure that allows light to enter through a substrate,
A substrate formed of a light transmissive material and receiving light;
A metal electrode provided on the substrate and provided with an electrode extraction portion capable of being connected to external wiring;
A transparent conductive layer formed on the substrate while covering a portion other than the electrode extraction portion of the metal electrode;
A buffer layer formed on the transparent conductive layer;
A light absorption layer composed of a chalcopyrite type compound semiconductor thin film formed on the buffer layer;
And a back electrode layer formed on the light absorption layer.   2. The chalcopyrite type compound semiconductor thin film of the light absorption layer is composed of a Cu—In—Se based semiconductor material containing copper (Cu), indium (In) and selenium (Se). The power generator described in 1.   The power generation body according to claim 1, wherein the buffer layer is formed on the transparent conductive layer by a sputtering method.   4. The power generator according to claim 1, wherein the metal electrode, the transparent conductive layer, the light absorption layer, and the back electrode layer are stacked on the substrate by a sputtering method. 5.   5. The power generator according to claim 1, wherein the electrode extraction portion of the metal electrode is provided on an end surface of the substrate.   The power generation body according to claim 1, wherein the electrode extraction portion of the metal electrode is provided on a light incident surface of the substrate. A method of manufacturing a power generator having a super straight structure,
A metal electrode forming step of forming a metal electrode on a substrate made of a light transmissive material;
A transparent conductive layer, a buffer layer, a light absorption layer, and a back surface are formed on the substrate by sputtering while leaving a part of the formed metal electrode as an electrode extraction portion and covering a portion other than the electrode extraction portion of the metal electrode. A thin film deposition step of sequentially depositing electrode layers,
The said light absorption layer is comprised from the chalcopyrite type compound semiconductor thin film containing copper (Cu), indium (In), and selenium (Se). The manufacturing method of the electric power generation body characterized by the above-mentioned.   The electrode extraction portion of the metal electrode covers the electrode extraction portion with an adhesion mask, and then the transparent conductive layer, the buffer layer, the light absorption layer, and the back electrode layer are sequentially formed on the metal electrode. The method of manufacturing a power generator according to claim 7.   The light absorption layer is formed by laminating a plurality of mixtures having different compositions containing at least Cu and In, or Cu and Se, or In and Se, and then melting and diffusing the mixtures with each other. It forms, The manufacturing method of the electric power generation body of Claim 7 or 8 characterized by the above-mentioned.

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