JP2011222589A - Photovoltaic device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic device which, having an effective light scattering effect, permits reduction of defects in a crystal-based thin-film semiconductor layer included in a photoelectric conversion layer compared to conventional art.SOLUTION: A photovoltaic device comprises a first electrode layer 12 having a texture structure, a photoelectric conversion layer 13, and a second electrode layer 17 which are laminated on a glass substrate 11 in this order. The photoelectric conversion layer 13 includes a first photoelectric conversion unit 14 and a second photoelectric conversion unit 16 composed of a crystal-based thin-film semiconductor layer, and has an intermediate layer 15 which, provided between the first and second photoelectric conversion units 14 and 16, reflects part of incident light while passing the remainder thereof and electrically connects between the first and second photoelectric conversion units 14 and 16. In the intermediate layer 15, fine particles 152 made of transparent conductive material are embedded in an intermediate layer medium 151 made of transparent conductive material, so that the surface on the side of the second electrode layer 17 is almost flattened.

Description

  The present invention relates to a photovoltaic device having a crystalline thin film semiconductor layer and a method for manufacturing the photovoltaic device.

  In a thin film solar cell in which a transparent conductive film, photoelectric conversion layer, and reflective conductive film are laminated on a glass substrate, a texture structure is formed on the transparent conductive film on the light incident side, and incident light is scattered to increase the optical path length. A structure that can efficiently use incident sunlight is adopted. Further, in such a thin film solar cell, a structure in which a plurality of photoelectric conversion units are stacked as a photoelectric conversion layer and a photoelectric conversion unit that absorbs light having a longer wavelength is disposed from the light incident side toward the opposite side. Therefore, a stacked thin film solar cell that efficiently converts incident light into a photoelectric conversion has also been proposed. In the case of stacked thin-film solar cells, an intermediate layer is provided between each photoelectric conversion unit to control the wavelength of light used by a plurality of photoelectric conversion units, balance the generated current, and improve conversion efficiency. (For example, refer to Patent Document 1).

  Further, in the laminated thin film solar cell, the transparent conductive film and the intermediate layer are embedded in the insulating light scatterer in a medium made of a transparent conductive material, thereby allowing the incident solar without providing a texture structure to the transparent conductive film. A structure that scatters light has been proposed. In such a structure, when forming a photoelectric conversion unit composed of a crystalline thin film semiconductor layer such as a microcrystalline silicon thin film, a flat photoelectric conversion unit is formed because there is no unevenness in the underlayer. (For example, refer to Patent Document 2).

JP2003-347572A (FIG. 1) JP 2006-128478 A (FIG. 5)

  By the way, in the technique described in Patent Document 1, a large texture structure is formed on the transparent conductive film or the glass substrate itself to effectively increase the optical path length and confine light. However, when a photoelectric conversion unit including a crystalline thin film semiconductor layer such as a microcrystalline silicon thin film is formed on a ground layer with large irregularities, there is a problem that defects in the crystalline thin film semiconductor layer increase. .

  In addition, in order to reduce the defects in the crystalline thin film semiconductor layer in order to solve such problems, it is necessary to flatten the glass substrate and the transparent conductive film on which sunlight is incident when attempting to realize a flat base layer. There is no choice but to diffuse the light by embedding a light scatterer in the transparent conductive film as in the technique described in Patent Document 2 above. However, the light scattering effect of the structure in which such a light scatterer is embedded in the underlayer is reduced as compared with the case where the texture structure is formed on the transparent conductive film or glass substrate described in Patent Document 1. There was a point. That is, with such a structure, it is not possible to obtain an effective light scattering effect as in a transparent conductive film or a glass substrate having a texture structure.

  The present invention has been made in view of the above, and in a photovoltaic device having a crystalline thin film semiconductor layer, while having an effective light scattering effect, the crystalline thin film semiconductor layer included in the photoelectric conversion layer It is an object of the present invention to obtain a photovoltaic device and a method for manufacturing the photovoltaic device that can reduce defects as compared with the related art.

  In order to achieve the above object, a photovoltaic device according to the present invention is a photovoltaic device in which a first electrode layer having a texture structure, a photoelectric conversion layer, and a second electrode layer are sequentially laminated on a substrate. The photoelectric conversion layer is provided between the plurality of photoelectric conversion units including at least a photoelectric conversion unit made of a crystalline thin film semiconductor layer, reflects a part of incident light, and An intermediate layer that transmits and electrically connects the plurality of photoelectric conversion units, and the first electrode layer than the photoelectric conversion unit made of a crystalline thin film semiconductor layer among the intermediate layers. The at least one intermediate layer formed on the side has a structure in which fine particles made of a transparent conductive material are embedded in an intermediate layer medium made of a transparent conductive material, and the surface on the second electrode layer side is substantially flattened. Characterized in that it has a.

  According to this invention, the intermediate layer provided between the photoelectric conversion units formed on the substrate having the texture structure or the transparent conductive film is formed by the intermediate layer medium made of the transparent conductive material including the fine particles made of the transparent conductive material. Since the conductive fine particles are embedded in the recesses of the underlayer, the upper surface of the intermediate layer that becomes the underlayer of the crystalline thin film semiconductor layer is substantially flattened. As a result, an effective light scattering effect is realized by the texture structure, and defects in the crystalline thin film semiconductor layer formed on the intermediate layer can be reduced as compared with the conventional case.

1 is a perspective view schematically showing an example of the structure of a photovoltaic device according to Embodiment 1 of the present invention. FIG. 2 is a sectional view schematically showing an example of the photovoltaic apparatus according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing the relationship between the amount of defects generated in the crystalline thin film semiconductor layer and the texture structure of the underlayer. FIGS. 4-1 is a perspective view which shows typically an example of the procedure of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 1). FIGS. 4-2 is a perspective view which shows typically an example of the procedure of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 2). FIGS. FIG. 5 is a diagram showing a transparent conductive material that can be used for the intermediate layer and its refractive index.

  Hereinafter, a photovoltaic device and a manufacturing method thereof according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments. In addition, the perspective view and cross-sectional view of the photovoltaic device used in the following embodiments are schematic, and the relationship between the thickness and width of the layers, the ratio of the thickness of each layer, and the like are different from the actual ones. .

Embodiment 1 FIG.
FIG. 1 is a perspective view schematically showing an example of the structure of a photovoltaic device according to Embodiment 1 of the present invention, and FIG. 2 is a schematic example of the photovoltaic device according to Embodiment 1 of the present invention. FIG. The thin film solar cell 10 as the photovoltaic device has a structure in which a first electrode layer 12, a photoelectric conversion layer 13, and a second electrode layer 17 are sequentially stacked on a substrate 11. Here, it is assumed that light subjected to photoelectric conversion is incident from the substrate 11 side.

  Since the board | substrate 11 is located in the incident side of light, it is comprised with materials, such as glass, organic film, and ceramics which have transparency. In addition, since the first electrode layer 12, the photoelectric conversion layer 13, and the second electrode layer 17 are formed on the substrate 11, the substrate 11 has a melting point higher than the film formation temperature of the first electrode layer 12 and the like. It is desirable that the material has

The first electrode layer 12 includes a transparent conductive oxide film such as zinc oxide (ZnO), indium tin oxide (hereinafter referred to as ITO), tin oxide (SnO ₂ ), aluminum (Al) as a dopant, At least selected from gallium (Ga), indium (In), boron (B), yttrium (Y), silicon (Si), zirconium (Zr), titanium (Ti), fluorine (F), nitrogen (N), etc. It is composed of a transparent conductive material such as a ZnO film, an ITO film, or a SnO ₂ film using one or more elements. Further, a texture structure (uneven structure) is formed on the upper surface of the first electrode layer 12 to efficiently scatter and confine light incident on the thin-film solar cell 10.

  The photoelectric conversion layer 13 includes a plurality of photoelectric conversion units and an intermediate layer formed between two photoelectric conversion units adjacent in the stacking direction. In this example, the photoelectric conversion layer 13 has a structure in which a first photoelectric conversion unit 14, an intermediate layer 15, and a second photoelectric conversion unit 16 are sequentially stacked on the first electrode layer 12.

  The first photoelectric conversion unit 14 is constituted by a thin film semiconductor layer having an amorphous pin structure, for example, amorphous silicon, amorphous silicon germanium, amorphous silicon oxide, amorphous silicon carbide, or the like. Since the 1st photoelectric conversion unit 14 is formed on the 1st electrode layer 12 in which the texture structure was formed, it receives the influence of a foundation | substrate and the upper surface is not flat but has an uneven structure.

  The intermediate layer 15 is made of a transparent conductive material having a function of partially reflecting and partially transmitting light incident from the substrate 11 side. More specifically, the intermediate layer 15 reflects light in a wavelength range that can be absorbed by the first photoelectric conversion unit 14 out of light incident from the substrate 11 side to the first photoelectric conversion unit 14 side. It is desirable to have a function of transmitting light in the wavelength range to the second photoelectric conversion unit 16 side.

  The intermediate layer 15 has a structure in which the intermediate layer medium 151 made of conductive silicon oxide includes fine particles 152 made of crystalline silicon oxide having conductivity. Specifically, the upper surface of the first photoelectric conversion unit 14 and the lower surface of the second photoelectric conversion unit 16 are connected while filling the concave portion of the concavo-convex structure formed on the upper surface of the first photoelectric conversion unit 14. The fine particles 152 are arranged so that the intermediate layer medium 151 is formed so as to fill the space between the fine particles 152. Here, the intermediate layer medium 151 can be set to a thickness of 20 to 150 nm, for example, and the fine particles 152 have a diameter smaller than the thickness of the intermediate layer 15 to be formed. By adopting such a structure, the upper surface of the intermediate layer 15 has a smoother (flat) structure than the upper surface of the first photoelectric conversion unit 14, and the first photoelectric conversion unit 14 and the second photoelectric conversion unit 14 Electrical connection with the photoelectric conversion unit 16 is ensured.

  The second photoelectric conversion unit 16 is composed of a crystalline thin film semiconductor layer having a pin structure, such as microcrystalline silicon, microcrystalline silicon germanium, or microcrystalline silicon carbide. Since the second photoelectric conversion unit 16 is formed on the intermediate layer 15 having a flat upper surface as compared with the upper surface of the texture structure on the upper surface of the first photoelectric conversion unit 14, it is formed inside the crystalline thin film semiconductor layer. Defects are unlikely to occur. As a result, the quality of the second photoelectric conversion unit 16 can be improved and the conversion efficiency can be improved.

The second electrode layer 17 has a structure in which a transparent conductive film 171 and a light reflective conductive film 172 formed immediately above the photoelectric conversion layer 13 are stacked. The transparent conductive film 171 is preferably made of a transparent conductive material that does not absorb light in the wavelength range that has passed without being absorbed by the photoelectric conversion layer 13. A material for such a transparent conductive film 171 is selected from a transparent conductive oxide film such as ZnO, ITO, SnO ₂ , and a dopant selected from Al, Ga, In, B, Y, Si, Zr, Ti, F, N, and the like. Examples thereof include transparent conductive materials such as ZnO films, ITO films, and SnO ₂ films using at least one kind of element.

  The light-reflecting conductive film 172 has a role of reflecting light that has passed through the photoelectric conversion layer 13 without being absorbed, in addition to having a function of extracting a photoelectrically converted current. Examples of such a material for the light reflective conductive film 172 include silver (Ag), Ti, Al, and molybdenum (Mo).

  In FIG. 1, a region where the photoelectric conversion layer 13 and the second electrode layer 17 are removed at a part on the substrate 11 and the first electrode layer 12 is exposed is a contact portion 21. By attaching an external extraction electrode (not shown) on the contact portion 21 and the second electrode layer 17, the current generated by the photoelectric conversion layer 13 on the substrate 11 is extracted to the outside.

  In the above description, the case where the texture structure is provided on the first electrode layer 12 is shown. However, the first electrode layer 12 can also be formed by forming the first electrode layer 12 on the substrate 11 provided with the texture structure. A texture structure can be provided on the top surface of layer 12.

  FIG. 3 is a diagram showing the relationship between the amount of defects generated in the crystalline thin film semiconductor layer and the texture structure of the underlayer. This figure is published in the literature (M. Python et al, “Influence of the substrate geometrical parameters on microcrystalline silicon growth for thin-film solar cells”, Solar Energy Materials & Solar Cells 93 (2009), p1714-1720). It is a figure. FIG. 3 shows the result of numerical calculation of the dependence of the amount of defects (cracks) generated in the microcrystalline semiconductor film on the radius of curvature of the texture structure of the substrate and the angle α of the pyramid structure. FIG. 3A shows the shape of the texture structure to be simulated. Here, an angle formed with the substrate surface when the side surface of the pyramid structure forming the texture structure is extended is α. Further, the side surfaces of adjacent pyramid structures are connected by a curved connection surface. Then, the simulation is performed by variously changing the angle α and the curvature radius of the connection surface, and the amount of defects generated in the microcrystalline semiconductor film is calculated. The result is shown in FIG. In FIG. 3B, the horizontal axis represents the radius of curvature of the connecting surface connecting the side surfaces of the pyramid structure, and the vertical axis represents the amount of defects generated in the microcrystalline semiconductor film.

  As shown in FIG. 3B, as the angle α of the side surface of the pyramid structure formed on the substrate becomes smaller and the radius of curvature of the connecting surface between the pyramid structures becomes larger, the microcrystal formed on the upper part thereof. It can be seen that the amount of defects generated in the semiconductor film decreases. However, such a substrate has a small effect of scattering light incident from the substrate side and increasing the optical path length. Therefore, when using such a substrate, the film thickness of the photoelectric conversion layer formed on the substrate must be increased. As a result, the built-in electric field is lowered and the output voltage is reduced.

  On the other hand, in Embodiment 1, the photoelectric conversion layer 13 is formed on the substrate 11 (first electrode layer 12) where the angle α of the side surface of the pyramid structure is large and the curvature radius of the connection surface between the pyramid structures is small. In the case of forming the microparticles 152, the fine particles 152 made of conductive crystalline silicon oxide are formed so as to fill the concave portions of the first photoelectric conversion unit 14 in which the texture structure is formed, and the conductive oxide is filled so as to fill the spaces between the fine particles 152. An intermediate layer medium 151 made of silicon was formed. Thereby, the upper surface of the intermediate layer 15 can be made smooth (flat), and the occurrence of defects in the second photoelectric conversion unit 16 made of a crystalline thin film semiconductor layer formed on the intermediate layer 15 is suppressed. It becomes possible. That is, on the light incident side, the photoelectric conversion layer 13 having a crystalline thin film semiconductor layer with few defects can be formed while forming a texture structure with a large light scattering effect.

  Here, an outline of the operation in the thin film solar cell 10 having such a structure will be described. Incident light such as sunlight incident from the substrate 11 side is scattered by the first electrode layer 12 having a textured structure, so that the inside of the first and second photoelectric conversion units 14 and 16 is perpendicular to the substrate surface. Progress diagonally with respect to the direction. That is, the first and second photoelectric conversion units 14 and 16 have a longer optical path length than when no texture structure is formed in the first electrode layer 12.

  Light incident on the first and second photoelectric conversion units 14 and 16 generates free carriers in the i-type semiconductor layers in the first and second photoelectric conversion units 14 and 16, respectively. The generated free carriers are transported in the photoelectric conversion layer 13 by a built-in electric field formed by the p-type semiconductor layer and the n-type semiconductor layer in the first and second photoelectric conversion units 14 and 16, and a current is generated. . The generated current is taken out from the first electrode layer 12 and the second electrode layer 17.

  In addition, incident light that has entered the photoelectric conversion layer 13 but has not been subjected to photoelectric conversion here passes through the transparent conductive film 171 of the second electrode layer 17, and again returns to the photoelectric conversion layer 13 side by the light reflective conductive film 172. It is reflected to. A part of the light incident on the photoelectric conversion layer 13 again is photoelectrically converted here.

  Further, the light that has not been subjected to photoelectric conversion by the photoelectric conversion layer 13 reaches the first electrode layer 12. A texture structure is formed in the first electrode layer 12, and a part of the light reaching the first electrode layer 12 is reflected again to the photoelectric conversion layer 13 by the uneven portion of the texture structure. By repeating such steps, photoelectric conversion is performed by the thin-film solar cell 10 and current (voltage) is taken out to the outside.

  Next, a method for manufacturing the thin film solar cell 10 having such a structure will be described. 4-1 to 4-2 are perspective views schematically showing an example of the procedure of the method for manufacturing the thin-film solar battery according to Embodiment 1 of the present invention. First, as shown in FIG. 4A, the first electrode layer 12 is formed on the substrate 11 by a film forming method such as a vacuum deposition method, a sputtering method, or a CVD (Chemical Vapor Deposition) method. For example, a ZnO film can be used as the first electrode layer 12. A texture structure is formed on the upper surface of the first electrode layer 12. The texture structure can be formed, for example, by depositing the first electrode layer 12 and performing wet etching using an acidic solution such as an aqueous hydrochloric acid solution or an alkaline solution such as a sodium hydroxide solution as an etching solution. In addition, by forming a texture structure in advance on the substrate 11 and forming the first electrode layer 12 on the substrate 11 on which the texture structure is formed, the first electrode layer 12 is formed by being influenced by the underlying layer. Thus, a texture structure can be formed on the upper surface.

  Next, as shown in FIG. 4B, the amorphous thin film semiconductor layer having the pin structure is formed on the first electrode layer 12 having the texture structure by a film forming method such as a plasma CVD method. The first photoelectric conversion unit 14 is formed. For example, an amorphous silicon film can be used as the first photoelectric conversion unit 14. Since the 1st photoelectric conversion unit 14 is formed on the base layer (1st electrode layer 12) in which the texture structure was formed, the uneven structure corresponding to the unevenness | corrugation of a base is formed in the upper surface.

Next, as shown in FIG. 4C, the intermediate layer 15 is formed on the first photoelectric conversion unit 14 by a sol-gel method. Here, a sol solution is prepared using ion-exchanged water (H ₂ O) and ethyl alcohol (C ₂ H ₅ OH) as a solvent and tetraethoxysilane (Si (C ₂ H ₅ O) ₄ , TEOS) as a raw material. The resulting sol solution is mixed with fine particles of conductive crystalline silicon oxide. For example, the substrate 11 on which the first photoelectric conversion unit 14 is formed is immersed in this sol solution, dried, and then subjected to heat treatment at a temperature of 300 ° C. or lower to sinter the intermediate layer 15. . In the intermediate layer 15, the fine particle 152 enters the concave portion of the texture structure, and the intermediate layer medium 151 is formed so as to fill the space between the fine particles 152. At this time, when the sol solution is formed on the substrate 11 (first photoelectric conversion unit 14), the surface flatness is improved due to the fluidity of the material. As a result, the intermediate layer 15 made of a smooth film that is not affected by the unevenness of the underlayer is obtained.

  Thereafter, as shown in FIG. 4A, the second photoelectric layer composed of the crystalline thin film semiconductor layer having the pin structure is formed on the intermediate layer 15 having a flat upper surface by a film forming method such as a plasma CVD method. A conversion unit 16 is formed. For example, a microcrystalline silicon film can be used as the second photoelectric conversion unit 16. Since the second photoelectric conversion unit 16 is formed on a flat underlayer (intermediate layer 15), the upper surface thereof has a flat structure, and the number of defects generated in the film is such that the number of defects in the film is uneven. Less than when formed above. Thereby, the photoelectric conversion layer 13 in which the first photoelectric conversion unit 14, the intermediate layer 15, and the second photoelectric conversion unit 16 are stacked is formed.

  Next, as shown in FIG. 4B, the second electrode layer 17 is formed on the second photoelectric conversion unit 16. Specifically, a transparent conductive film 171 made of a transparent conductive material and a light reflective conductive film 172 are sequentially stacked on the second photoelectric conversion unit 16 by a film forming method such as a sputtering method. As the transparent conductive film 171, for example, a ZnO film can be used, and as the light reflective conductive film 172, for example, an Ag film can be used.

  Thereafter, the photoelectric conversion layer 13 is removed from the second electrode layer 17 in a predetermined region by a laser scribing method, the first electrode layer 12 is exposed, and a contact portion (not shown) is formed. Then, a contact is formed on the contact portion and the second electrode layer 17 so as to be connected to an external extraction wiring for extracting an electric current to the outside. As described above, the thin film solar cell 10 shown in FIGS. 1 to 2 is manufactured.

  In the above description, the intermediate layer 15 is formed by the sol-gel method. However, the intermediate layer 15 may be formed by other methods as long as the upper surface of the intermediate layer 15 can be planarized. .

  Here, the case where the intermediate layer 15 is formed by the sol-gel method without mixing fine particles made of conductive crystalline silicon oxide into the sol solution will be described with reference to FIG. The manufacturing process of the thin film solar cell 10 is generally performed within a temperature range of 100 to 300 ° C. from the relationship between the heat resistance temperature of the substrate 11 (glass substrate) and the optimum deposition temperature of the silicon-based thin film. desirable. A sol solution is formed using tetraethoxysilane as a raw material and ion-exchanged water and ethyl alcohol as a solvent, and after immersing the substrate 11 on which the first photoelectric conversion unit 14 is formed in this sol solution, the solvent is added. Evaporate at 200-300 ° C. Even with only the film (intermediate layer medium) generated at this time, it is possible to improve the flatness by utilizing the fluidity of the material, but sufficient conductivity, particularly the first and second photoelectric conversion units 14. In order to ensure electrical conductivity in the thickness direction for electrical connection between the first and second electrodes 16, crystalline silicon oxide is required. Therefore, in order to crystallize silicon oxide (SiO) contained in the film, heat treatment must be performed at a temperature of 600 ° C. or higher after drying. As a result of this heat treatment, the characteristics of the first photoelectric conversion unit 14 (amorphous silicon film) formed at a substrate temperature of 200 ° C. or lower deteriorate.

  For this reason, a method for producing a flat and conductive intermediate layer 15 at a temperature at which the characteristics of the first photoelectric conversion unit 14 made of an amorphous thin film semiconductor layer do not deteriorate, for example, a temperature of 300 ° C. or lower, is desired. It was rare. Therefore, in the first embodiment, as described above, conductive crystalline silicon oxide fine particles 152 are mixed in the sol solution, and these fine particles 152 are arranged in contact with each other in the thickness direction in the intermediate layer medium 151. It was made to be. Thus, an intermediate layer whose upper surface is flattened while ensuring conductivity between the first and second photoelectric conversion units 14 and 16 without heating above the temperature at which the characteristics of the amorphous thin film semiconductor layer deteriorate. 15 can be formed.

  In the first embodiment, the first photoelectric conversion unit 14 made of an amorphous thin film semiconductor layer is formed on the first electrode layer 12 having a texture structure with a high light scattering effect, and the first photoelectric conversion unit 14 is formed. The intermediate layer 15 in which fine particles 152 of crystalline silicon oxide having conductivity are arranged in the intermediate layer medium 151 is formed. As a result, the upper surface of the intermediate layer 15 is flattened without being affected by the underlying layer, and the second photoelectric conversion unit 16 formed thereon becomes a crystalline thin film semiconductor layer with few defects. As a result, the fill factor of the second photoelectric conversion unit 16 is improved, and the conversion efficiency can be improved. That is, there is an effect that the thin film solar cell 10 including the photoelectric conversion layer 13 including the crystalline thin film semiconductor layer with few defects can be obtained while having a texture structure having an effective light scattering effect.

  In addition, since the intermediate layer 15 is formed by a sol-gel method using a sol solution having crystalline silicon oxide fine particles having conductivity, the substrate 11 (first photoelectric conversion unit 14) is fluidized in the process until drying. The effect is that a flattened film can be obtained. Further, since fine particles of crystalline silicon oxide having conductivity that connect between the first and second photoelectric conversion units 14 and 16 are included, the intermediate layer medium 151 formed by drying is heated at a high temperature. There is no need for heat treatment. As a result, there is also an effect that the photoelectric conversion characteristics of the first photoelectric conversion unit 14 configured by the amorphous thin film semiconductor layer are not deteriorated.

Embodiment 2. FIG.
In the first embodiment, the case where the intermediate layer medium 151 and the fine particles 152 constituting the intermediate layer 15 are made of the same material has been described. In the second embodiment, a case where the intermediate layer medium 151 and the fine particles 152 constituting the intermediate layer 15 are made of different materials will be described. In the second embodiment, the configuration of the photovoltaic device is the same as that of the first embodiment shown in FIGS.

FIG. 5 is a diagram showing a transparent conductive material that can be used for the intermediate layer and its refractive index. As shown in FIG. 5, zinc oxide, tin oxide, silicon oxide, titanium oxide, magnesium fluoride, or the like can be used as the transparent conductive material. Although the refractive index value varies somewhat depending on the composition ratio of each material, a material having a refractive index smaller than the refractive index n _Si = 3.5 of silicon which is a semiconductor material constituting the photoelectric conversion layer 13 is used. The intermediate layer medium 151 may be selected, and a material having a different refractive index may be selected as the fine particles 152. By selecting such a combination of materials, the incident light can be scattered at the interface between the intermediate layer medium 151 and the fine particles 152 also in the intermediate layer 15. The transparent conductive material shown in FIG. 5 is an example, and the fine particles 152 are transparent and conductive with respect to sunlight, and have a small amount of light absorption with respect to the wavelength region of sunlight used in the thin film solar cell 10. Any material can be used without being limited to the materials shown in FIG.

  In the second embodiment, a transparent conductive material having a refractive index smaller than the refractive index of the semiconductor layer (photoelectric conversion layer 13) is used as the intermediate layer medium 151, and the intermediate layer medium 151 is used as the fine particles 152. A light scattering effect was added to the intermediate layer 15 using transparent conductive materials having different refractive indexes. As a result, the optical path length of the scattered light in the photoelectric conversion layer 13 can be increased as compared with the case of Embodiment 1, and the light can be reflected and transmitted and scattered without loss. . As a result, the effect that the utilization efficiency of sunlight can be improved can be obtained in addition to the effect of the first embodiment.

  In the first and second embodiments, the case where the photoelectric conversion layer 13 is configured by the two photoelectric conversion units 14 and 16 and the one intermediate layer 15 sandwiched therebetween is shown. However, the present invention is not limited to these embodiments, and a photoelectric conversion layer having a plurality of photoelectric conversion units of three or more layers and an intermediate layer sandwiched between two photoelectric conversion units adjacent in the stacking direction It can apply with respect to the thin film solar cell 10 provided with 13. FIG. In this case, among the photoelectric conversion units, the first electrode layer 12 side rather than the photoelectric conversion unit composed of the crystalline thin film semiconductor layer disposed closest to the first electrode layer 12 side where the texture structure is formed. The at least one intermediate layer arranged in the above may be constituted by an intermediate layer medium in which fine particles are arranged.

  As described above, the photovoltaic device according to the present invention is useful for a thin film solar cell including a photoelectric conversion layer including a crystalline thin film semiconductor layer on an electrode layer in which a texture structure is formed.

DESCRIPTION OF SYMBOLS 10 Thin film solar cell 11 Substrate 12 1st electrode layer 13 Photoelectric conversion layer 14 1st photoelectric conversion unit 15 Intermediate layer 16 2nd photoelectric conversion unit 17 2nd electrode layer 21 Contact part 151 Intermediate layer medium 152 Fine particle 171 Transparent Conductive film 172 Light reflective conductive film

Claims (7)

In a photovoltaic device in which a first electrode layer having a texture structure, a photoelectric conversion layer, and a second electrode layer are sequentially laminated on a substrate,
The photoelectric conversion layer is provided between a plurality of photoelectric conversion units including at least a photoelectric conversion unit made of a crystalline thin film semiconductor layer, and reflects a part of incident light and transmits the rest. And an intermediate layer for electrically connecting the plurality of photoelectric conversion units,
Among the intermediate layers, at least one intermediate layer formed on the first electrode layer side of the photoelectric conversion unit formed of a crystalline thin film semiconductor layer has fine particles formed of a transparent conductive material formed of a transparent conductive material. A photovoltaic device, characterized in that the photovoltaic device has a structure embedded in an intermediate layer medium, and the surface on the second electrode layer side is substantially flattened.   The photovoltaic device according to claim 1, wherein the fine particles and the intermediate layer medium are made of the same material.   The photovoltaic device according to claim 1, wherein the fine particles and the intermediate layer medium are made of different materials.   4. The photovoltaic device according to claim 2, wherein the intermediate layer medium is made of a material having a refractive index smaller than a refractive index of a material constituting the photoelectric conversion unit. 5.   The photovoltaic device according to claim 1, wherein the fine particles have a diameter smaller than a thickness of the intermediate layer.   The fine particles and the intermediate layer medium are made of a material selected from the group consisting of zinc oxide, tin oxide, silicon oxide, titanium oxide, and magnesium fluoride. A photovoltaic device according to claim 1. In the method of manufacturing a photovoltaic device in which a first electrode layer having a texture structure, a photoelectric conversion layer, and a second electrode layer are sequentially laminated on a substrate,
The step of forming the photoelectric conversion layer and covering the upper surface of the first photoelectric conversion unit having a texture structure with a solution in which fine particles made of a transparent conductive material are mixed in a medium that becomes a transparent conductive material after sintering,
Sintering the solution and forming an intermediate layer whose upper surface is flattened as compared to the first photoelectric conversion unit;
Forming the photoelectric conversion layer on the intermediate layer and forming a second photoelectric conversion unit comprising a crystalline thin film semiconductor layer;
A method for manufacturing a photovoltaic device, comprising:

Images