JP5642005B2 - PHOTOELECTRIC CONVERSION DEVICE, ITS MANUFACTURING METHOD, AND PHOTOELECTRIC CONVERSION MODULE - Google Patents

Description

  The present invention relates to a photoelectric conversion device, a manufacturing method thereof, and a photoelectric conversion module.

  2. Description of the Related Art Conventionally, a solar cell is configured by using a photoelectric conversion device including a light absorption layer such as a chalcopalite-based CIGS as a constituent unit and connecting the photoelectric conversion devices in series or in parallel on a substrate such as glass. .

  In this photoelectric conversion device, a buffer layer is provided on the light receiving surface, that is, on the light absorption layer. The buffer layer contained sulfur that was chemically grown from a solution by a solution deposition method (CBD method) or the like in order to reduce the burden on the environment and to obtain a suitable heterojunction with the light absorption layer. A zinc mixed crystal compound semiconductor film is used.

  Further, for example, a zinc oxide film is provided as a transparent electrode on the buffer layer (see Patent Document 1).

Japanese Patent Laid-Open No. 08-330614

  However, even with a photoelectric conversion device as shown in Patent Document 1 and a photoelectric conversion module using the photoelectric conversion device, the reliability with respect to the leak current is low depending on the application, and the photoelectric conversion efficiency decreases due to secular change. There was a case.

  The present invention has been completed in view of the above-described conventional problems, and an object thereof is to provide a highly reliable photoelectric conversion device and a photoelectric conversion module that can maintain high conversion efficiency.

A photoelectric conversion device according to an embodiment of the present invention includes a light absorption layer including a compound semiconductor capable of photoelectric conversion, a first semiconductor layer including a chalcogenide of In provided on one surface of the light absorption layer, A second semiconductor layer containing Zn chalcogenide and In provided on a surface of the first semiconductor layer opposite to the light absorption layer; and a second semiconductor layer opposite to the light absorption layer. And a transparent electrode layer containing In provided on the surface, wherein the second semiconductor layer has a minimum value of the In composition ratio in the vicinity of the interface with the first semiconductor layer.

  Furthermore, a photoelectric conversion module according to an embodiment of the present invention includes a plurality of the above-described photoelectric conversion devices, and the adjacent photoelectric conversion devices are electrically connected.

Furthermore, a method for manufacturing a photoelectric conversion device according to an embodiment of the present invention includes a first step of forming a first semiconductor layer containing a chalcogenide of In on a light absorption layer containing a compound semiconductor capable of photoelectric conversion, A second step of forming an intermediate layer containing a chalcogenide of Zn on the surface of the first semiconductor layer; a third step of forming a transparent conductive layer containing In on the surface of the intermediate layer; and reducing the transparent electrode layer And a fourth step of diffusing In from the transparent electrode layer into the intermediate layer by heat treatment in an atmosphere.

According to another embodiment of the present invention, there is provided a method for manufacturing a photoelectric conversion device, the first step of forming a first semiconductor layer containing a chalcogenide of In on a light absorption layer containing a compound semiconductor capable of photoelectric conversion, A second step of forming an intermediate layer containing a chalcogenide of Zn on the surface of the first semiconductor layer; and a step of diffusing In from the solution into the intermediate layer by immersing the intermediate layer in a solution containing In. 3 steps.

  According to the present invention, the photoelectric conversion efficiency can be maintained high by suppressing the increase in conductivity of the second semiconductor layer in the process of using the photoelectric conversion device and reducing the leak current. It is possible to obtain a photoelectric conversion device and a photoelectric conversion module having high reliability capable of satisfying the requirements.

It is sectional drawing which shows an example of embodiment of the photoelectric conversion apparatus and photoelectric conversion module which concern on this invention. It is sectional drawing which shows the other example of embodiment of the photoelectric conversion apparatus and photoelectric conversion module which concern on this invention. It is a perspective view of embodiment of the photoelectric conversion apparatus and photoelectric conversion module which concern on this invention of FIG. It is a graph which shows the composition distribution of In after the heat processing in the semiconductor layer and light absorption layer of one Embodiment of this invention.

  Hereinafter, an embodiment of a photoelectric conversion device, a manufacturing method thereof, and a photoelectric conversion module according to the present invention will be described in detail with reference to the drawings.

(Photoelectric conversion device)
The photoelectric conversion device 10 includes a substrate 1, a first electrode layer 2, a light absorption layer 3, a semiconductor layer 4, and a second electrode layer 5 (hereinafter also referred to as a transparent electrode layer 5). Is done.

  The semiconductor layer 4 includes a first semiconductor layer 4a on the light absorption layer 3 side and a second semiconductor layer 4b on the transparent electrode layer 5 side. The semiconductor layer 4 is a layer that performs a heterojunction with the light absorption layer 3. The semiconductor layer 4 is formed on the light absorption layer 3 with a thickness of about 5 nm to 200 nm. The light absorption layer 3 and the semiconductor layer 4 are preferably of different conductivity types. For example, when the light absorption layer 3 is a p-type semiconductor, the semiconductor layer 4 is an n-type semiconductor. Preferably, from the viewpoint of reducing the leakage current, the semiconductor layer 4 is a layer having a resistivity of 1 Ω · cm or more. Moreover, in order to improve the absorption efficiency of the light absorption layer 3, the semiconductor layer 4 preferably has a light transmission property with respect to the wavelength region of light absorbed by the light absorption layer 3.

  In FIG. 1, a plurality of photoelectric conversion devices 10 are formed side by side. The photoelectric conversion device 10 includes a third electrode layer 6 provided on the substrate 1 side of the light absorption layer 3 so as to be separated from the first electrode layer 2. The transparent electrode layer 5 and the third electrode layer 6 are electrically connected by the connection conductor 7 provided in the light absorption layer 3. The third electrode layer 6 is integrated with the first electrode layer 2 of the adjacent photoelectric conversion device 10. With this configuration, adjacent photoelectric conversion devices 10 are connected in series. In one photoelectric conversion device 10, the connection conductor 7 is provided so as to penetrate the light absorption layer 3 and the semiconductor layer 4, and light sandwiched between the first electrode layer 2 and the transparent electrode layer 5. Photoelectric conversion is performed between the absorption layer 3 and the semiconductor layer 4.

  The substrate 1 is for supporting the photoelectric conversion device 10. Examples of the material used for the substrate 1 include glass, ceramics, resin, and metal.

  The first electrode layer 2 and the third electrode layer 6 are made of a conductor such as Mo, Al, Ti, or Au, and are formed on the substrate 1 by a sputtering method or a vapor deposition method.

  The transparent electrode layer 5 is a 0.05 to 3 μm transparent conductive film such as ITO or ZnO. The transparent electrode layer 5 is formed by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like. The transparent electrode layer 5 is a layer having a resistivity lower than that of the semiconductor layer 4, and is for taking out charges generated in the light absorption layer 3. From the viewpoint of taking out charges well, it is preferable that the resistivity of the transparent electrode layer 5 is less than 1 Ω · cm and the sheet resistance is 50 Ω / □ or less.

  In order to increase the absorption efficiency of the light absorption layer 3, the transparent electrode layer 5 preferably has a light transmittance with respect to the absorption light of the light absorption layer 3. The transparent electrode layer 5 has a thickness of 0.05 to 0.5 μm from the viewpoint of enhancing the light transmittance and at the same time enhancing the light reflection loss prevention effect and the light scattering effect, and further transmitting the current generated by the photoelectric conversion. It is preferable to do this. Further, from the viewpoint of preventing light reflection loss at the interface between the transparent electrode layer 5 and the semiconductor layer 4, the refractive indexes of the transparent electrode layer 5 and the semiconductor layer 4 are preferably equal.

  Next, another example of the embodiment of the photoelectric conversion device of the present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view of a photoelectric conversion device 20 according to another embodiment, and FIG. 3 is a perspective view of the photoelectric conversion device 20. 2 and 3 are different from the photoelectric conversion device 10 in FIG. 1 in that a collecting electrode 8 is formed on the transparent electrode layer 5. 2 and 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and as in FIG. 1, a plurality of photoelectric conversion devices 20 are connected to constitute a photoelectric conversion module 21. .

A photoelectric conversion device according to an embodiment of the present invention includes a light absorption layer including a compound semiconductor capable of photoelectric conversion, a first semiconductor layer including a chalcogenide of In provided on one surface of the light absorption layer, A second semiconductor layer containing Zn chalcogenide and In provided on a surface of the first semiconductor layer opposite to the light absorption layer; and a second semiconductor layer opposite to the light absorption layer. And a transparent electrode layer containing In provided on the surface, wherein the second semiconductor layer has a minimum value of the In composition ratio in the vicinity of the interface with the first semiconductor layer.

  In FIG. 4, the vertical axis is In atomic% with respect to the total composition of the light absorption layer 3 and the semiconductor layer 4, and the horizontal axis is when the interface between the light absorption layer 3 and the first semiconductor layer 4 a is the origin (0). The distance is shown, and the light absorption layer side is +, and the first semiconductor layer 4a side is-. For example, in the vicinity of the interface between the second semiconductor layer 4b and the first semiconductor layer 4a (near −30 nm, that is, the portion surrounded by the dotted circle in FIG. 4), the In composition ratio has a minimum value. Yes.

  By having the lowest conductivity in this minimum value region, the leak current from the light absorption layer 3 to the semiconductor layer 4 is reduced, and the reliability with high photoelectric conversion efficiency is obtained.

  In addition, the region of the minimum value buffers In diffusion from the transparent electrode layer 5 side due to secular change, and can suppress unnecessary diffusion of In to the first semiconductor layer 4a. As a result, it is possible to maintain a good pn junction between the light absorption layer 3 and the first semiconductor layer 4a, and to obtain high reliability with high photoelectric conversion efficiency.

  In addition, since In is contained in advance on the transparent electrode 5 side of the second semiconductor layer 4b, diffusion of In from the transparent electrode layer 5 to the second semiconductor layer 4b can be reduced. As a result, it is possible to reduce the generation of a large leak current due to the diffusion of In from the transparent electrode 5 due to aging progressing locally in the second semiconductor layer 4b.

In addition, when the composition of In changes from the transparent electrode layer 5 to the semiconductor layer 4 intermittently, it causes a sudden change in transmittance and refractive index, resulting in reflection of absorbed light. It is preferable that the composition ratio of In changes gradually and continuously in the film thickness direction.

The photoelectric conversion device according to an embodiment of the present invention, the first semiconductor layer comprises a chalcogenide of In, the second semiconductor layer that contains a chalcogenide Zn.

Examples of In chalcogenides include In ₂ S ₃ , In ₂ Se ₃ , and In ₂ Te ₃ . A semiconductor containing such a chalcogenide of In has high durability under a high temperature and high humidity environment and is hardly deteriorated.

  The second semiconductor layer 4b is a semiconductor containing a Zn chalcogenide, and the Zn chalcogenide is ZnS, ZnSe, or ZnTe. Zn hydroxide or Zn oxide may be included. Preferably, 60% or more of the total number of moles of Zn constituting the second semiconductor layer 4b is a chalcogenide of Zn. Such a semiconductor containing a chalcogenide of Zn can improve the band matching with the light absorption layer 3 and can increase the photoelectric conversion efficiency.

  The first semiconductor layer 4a and the second semiconductor layer 4b are sequentially stacked on the light absorption layer 3, thereby having both high durability and high photoelectric conversion efficiency in a high temperature and high humidity environment. In addition, even when a photoelectric conversion device is manufactured with a large area, it is possible to prevent such durability and photoelectric conversion efficiency from varying depending on the in-plane position. Therefore, it is possible to increase the area of the photoelectric conversion device having excellent durability and photoelectric conversion characteristics.

  Furthermore, the first semiconductor layer 4a is preferably 5 to 100 nm. With such a thickness, the second semiconductor layer 4 b is formed close to the light absorption layer 3, so that band matching with the light absorption layer 3 is good and the light absorption layer 3 and the semiconductor layer 4 The charge separation function of the configured photoelectric conversion unit can be enhanced.

  Further, the second semiconductor layer 4a is preferably 5 to 100 nm. With such a thickness, it is possible to contribute to a reduction in leakage current, improve voltage, and improve performance. Moreover, the component which becomes resistance of extraction current can be suppressed, and performance can be improved.

  Furthermore, as a preferable form of the semiconductor layer 4 of the photoelectric conversion device according to one embodiment of the present invention, it is preferable that the first semiconductor layer contains indium sulfide and the second semiconductor layer contains zinc sulfide. As a result, band matching between the semiconductor layers 4 is improved, and charge transfer is improved. In particular, when the light absorption layer 3 is a chalcopyrite compound semiconductor made of an I-III-VI group compound semiconductor, the band matching of the light absorption layer 3 and the semiconductor layer 4 is particularly good, and the photoelectric conversion efficiency can be further increased. . Preferably, 60% or more of the total number of moles of In constituting the first semiconductor layer 4a is indium sulfide, and 60% or more of the total number of moles of Zn constituting the second semiconductor layer 4b. Zinc sulfide is preferred. Thereby, the durability of the entire semiconductor layer 4 in a high-temperature and high-humidity environment can be further enhanced.

Furthermore, the light absorption layer 3 of the photoelectric conversion device according to one embodiment of the present invention preferably includes a chalcopyrite material and has a function of absorbing light and generating a charge. The light absorption layer 3 is not particularly limited, but is preferably a chalcopyrite compound semiconductor from the viewpoint that high photoelectric conversion efficiency can be obtained even with a thin layer of 10 μm or less. An example of the chalcopyrite compound semiconductor is an I-III-VI group compound semiconductor. The group I-III-VI compound semiconductor is a group IB element (also referred to as a group 11 element), a group III-B element (also referred to as a group 13 element), and a group VI-B element (also referred to as a group 16 element). Compound semiconductor (also referred to as CIS compound semiconductor). Examples of the I-III-VI group compound semiconductor include Cu (In, Ga) Se ₂ (also referred to as CIGS), Cu (In, Ga) (Se, S) ₂ (also referred to as CIGSS), and CuInS ₂ (CIS). Also called). Cu (In, Ga) Se ₂ refers to a compound mainly composed of Cu, In, Ga, and Se. Cu (In, Ga) (Se, S) ₂ refers to a compound mainly composed of Cu, In, Ga, Se, and S.

  The II-VI group compound semiconductor is a compound semiconductor of a group II-B element (also referred to as a group 12 element) and a group VI-B element. Examples of the II-VI group compound semiconductor include ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, and the like.

  Such a light absorption layer 3 can be formed by the following method. First, a raw material element (for example, an IB group element, an II-B group element, a III-B group element, a VI-B group element, etc.) is formed into a film shape by sputtering or vapor deposition, or a film shape is formed by applying a raw material solution. To form a precursor containing raw material elements. And the light absorption layer 3 which consists of a semiconductor can be formed by heating this precursor. Alternatively, a metal element (for example, an IB group element, an II-B group element, an III-B group element, etc.) is formed into a film shape in the same manner as described above to form a precursor, and this precursor is converted into a VI-B group. It can also be formed by heating in a gas atmosphere containing an element.

(Photoelectric conversion module)
Furthermore, the photoelectric conversion module according to one embodiment of the present invention has a plurality of photoelectric conversion devices and electrically connects adjacent photoelectric conversion devices. That is, a plurality of photoelectric conversion devices 10 can be arranged and electrically connected to form a photoelectric conversion module 11. In order to easily connect adjacent photoelectric conversion devices 10 in series, as shown in FIG. 1, the photoelectric conversion device 10 is provided on the substrate 1 side of the light absorption layer 3 so as to be separated from the first electrode layer 2. The third electrode layer 6 is provided. The transparent electrode layer 5 and the third electrode layer 6 are electrically connected by the connection conductor 7 provided in the light absorption layer 3.

  The connection conductor 7 is preferably formed and integrated simultaneously when forming the transparent electrode layer 5. Thereby, while being able to simplify a process, the electrical connection reliability with the transparent electrode layer 5 can be improved. The connection conductor 7 connects the transparent electrode layer 5 and the third electrode layer 6, and is formed so as to divide the light absorption layers 3 of the adjacent photoelectric conversion devices 10. Each layer 3 can perform good photoelectric conversion, and current can be taken out in series connection.

(Manufacturing method of photoelectric conversion device)
Next, the manufacturing method of the photoelectric conversion apparatus of one Embodiment of this invention is demonstrated.

  A wet film forming method is used as a method for manufacturing the photoelectric conversion device. In this wet film forming method, a raw material solution is applied onto the light absorption layer 3 and chemically reacted by a treatment such as heating, or a method of depositing on the light absorption layer 3 by a chemical reaction in a solution containing the raw material. It is.

  By adopting such a method, the semiconductor layer 4 is diffused to some extent on the surface of the light absorption layer 3, and the heterojunction between the light absorption layer 3 and the semiconductor layer 4 can be made favorable with few defects. .

The manufacturing method of the photoelectric conversion device of one embodiment of the present invention includes a first step of forming a first semiconductor layer containing a chalcogenide of In on a light absorbing layer containing a compound semiconductor capable of photoelectric conversion, A second step of forming an intermediate layer containing Zn chalcogenide on the surface of the semiconductor layer, a third step of forming a transparent conductive layer containing In on the surface of the intermediate layer, and the transparent electrode layer in a reducing atmosphere. And a fourth step of diffusing In from the transparent electrode layer into the intermediate layer.

  In the fourth step, heat treatment is preferably performed at 150 to 250 ° C. for about 1 to 10 hours in a reducing atmosphere such as hydrogen.

  Accordingly, In actively diffuses from the transparent electrode layer 5 toward the intermediate layer, while In actively diffuses also from the first semiconductor layer 4a toward the intermediate layer, the first layer in the intermediate layer In the vicinity of the interface with the semiconductor layer 4a, a minimum value of the In composition ratio is formed, and the intermediate layer becomes the second semiconductor layer 4b.

Moreover, the manufacturing method of the photoelectric conversion device according to another embodiment of the present invention includes a first step of forming a first semiconductor layer containing a chalcogenide of In on a light absorption layer containing a compound semiconductor capable of photoelectric conversion, A second step of forming an intermediate layer containing a chalcogenide of Zn on the surface of the first semiconductor layer; and immersing the intermediate layer in a solution containing In to diffuse In from the solution into the intermediate layer. A third step.

  In the third step, the intermediate layer is immersed in a solution containing In. Preferably, after the intermediate layer is dried, the solution containing In is pressurized and immersed.

  As a result, In can be actively diffused into the intermediate layer, a minimum value of the composition ratio of In is formed in the vicinity of the interface with the first semiconductor layer 4a in the intermediate layer, and the intermediate layer is the second semiconductor. Layer 4b is formed.

  By the manufacturing method of these photoelectric conversion devices, In can be appropriately diffused in advance in the second semiconductor layer 4b, the leak current due to the diffusion of In over time can be reduced, and the photoelectric conversion efficiency can be improved. Large changes can be reduced.

1: Substrate 2: First electrode layer 3: Light absorption layer 4: Semiconductor layer 4a: First semiconductor layer 4b: Second semiconductor layer 5: Second electrode layer (transparent electrode layer)
6: third electrode layer 7: connecting conductor 8: current collecting electrode 9: photoelectric conversion body 10, 20: photoelectric conversion device 11, 21: photoelectric conversion module

Claims (6)

A light absorbing layer comprising a compound semiconductor capable of photoelectric conversion;
A first semiconductor layer containing a chalcogenide of In provided on one surface of the light absorption layer;
A second semiconductor layer containing Zn chalcogenide and In provided on a surface of the first semiconductor layer opposite to the light absorption layer;
A transparent electrode layer containing In provided on the surface of the second semiconductor layer opposite to the light absorption layer;
The photoelectric conversion device, wherein the second semiconductor layer has a minimum value of an In composition ratio in the vicinity of an interface with the first semiconductor layer. The photoelectric conversion device according to claim 1, wherein the first semiconductor layer includes indium sulfide, and the second semiconductor layer includes zinc sulfide. The light absorbing layer is a photoelectric conversion device according to claim 1 or 2 comprising a material of chalcopyrite. A plurality of photoelectric conversion device according to any one of claims 1 to 3 electrically connects the photoelectric conversion module of the photoelectric conversion device adjacent - le. A first step of forming a first semiconductor layer containing a chalcogenide of In on a light absorption layer containing a compound semiconductor capable of photoelectric conversion;
A second step of forming an intermediate layer containing a chalcogenide of Zn on the surface of the first semiconductor layer;
A third step of forming a transparent conductive layer containing In on the surface of the intermediate layer;
And a fourth step of diffusing In from the transparent electrode layer into the intermediate layer by heat-treating the transparent electrode layer in a reducing atmosphere. A first step of forming a first semiconductor layer containing a chalcogenide of In on a light absorption layer containing a compound semiconductor capable of photoelectric conversion;
A second step of forming an intermediate layer containing a chalcogenide of Zn on the surface of the first semiconductor layer;
And a third step of diffusing In from the solution into the intermediate layer by immersing the intermediate layer in a solution containing In.

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