JP2011199028A - Photovoltaic element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive photovoltaic element which has small environmental load during manufacture and has superior productivity and photoelectric conversion efficiency.SOLUTION: There is provided the inexpensive photovoltaic element which has small environmental load during manufacture and has the superior productivity and photoelectric conversion efficiency by providing a first electrode layer 2, a photoelectric conversion layer 4 for performing photoelectric conversion, and a second electrode layer 5 on substrates 1 and 9, and forming, in a film, a transparent electrode layer which has a flat surface and includes diffuse reflection regions 3 and 8 locally differing in refractive index from the electrode layers to diffuse and reflect light as an incident-side electrode between the first electrode layer 2 and the second electrode layer 5.

Description

  The present invention relates to a photovoltaic device and a manufacturing method thereof.

  Oil and other fossil fuels have supply concerns due to concerns about future depletion and carbon dioxide emissions that cause global warming. In recent years, the spread of solar power generation systems has been increasing due to increasing environmental awareness and lower system prices, and solar power generation is expected as an alternative to fossil fuels.

  Common solar cells are classified into bulk solar cells and thin film solar cells. Bulk solar cells are manufactured using bulk crystal semiconductors such as single crystal or polycrystalline silicon and gallium arsenide compounds, and many of them have already established mass production techniques. However, recently, bulk solar cells also have problems such as a shortage of raw materials due to a sudden increase in production volume of bulk solar cells and difficulty in cost reduction.

  Thin-film solar cells, on the other hand, have the potential to eliminate the shortage of raw materials and significantly reduce costs by significantly reducing the amount of semiconductor used, and are attracting attention as next-generation solar cells. Yes. Specifically, a bulk solar cell has a semiconductor substrate with a thickness of several hundreds μm, whereas a thin film solar cell has a semiconductor layer with a thickness of several μm to 10 μm.

  The structure of such a thin film solar cell can be generally classified into the following two types. That is, a transparent conductive layer, a photoelectric conversion layer (semiconductor layer), and a back electrode layer are sequentially laminated on a transparent substrate, and a super straight type in which light is incident from the translucent substrate side, and a back electrode on a non-transparent substrate This is a substrate type in which a layer, a photoelectric conversion layer (semiconductor layer), a transparent conductive film, and a metal grid electrode are sequentially laminated, and light enters from the electrode side of the metal grid.

  The former has a merit that, when a solar cell panel is installed on a roof of a house, etc., the glass surface becomes the front and protects the laminated film, and the construction / maintenance contractor can walk on the panel. In addition, the latter can provide a bendable solar cell panel regardless of the material and thickness of the substrate, and is advantageous in that it can be easily transported.

  As described above, the amount of semiconductor used in a thin-film solar cell is much smaller than that of a bulk solar cell. For this reason, in order to improve photoelectric conversion efficiency, high conversion efficiency must be obtained in the same volume. In order to obtain high photoelectric conversion efficiency in the same volume, a technology that effectively uses light incident on the semiconductor layer is very important.

  One technique for this purpose is an optical confinement technique. The light confinement technology is a substantial optical path in the photoelectric conversion layer by forming a structure that refracts and scatters light at the interface between the photoelectric conversion layer and a material having a refractive index different from that of the photoelectric conversion layer. This is a technique for increasing the light absorption amount by extending the length and improving the photoelectric conversion efficiency. Specifically, a technique for providing physical unevenness called texture is widely used. This technique is an optical confinement technique that increases the total amount of light passing through the semiconductor layer for generating electromotive force by irregularly reflecting incident light within the solar cell element.

  However, in the case of a textured structure with physical irregularities, defects in the semiconductor layer, especially in the convex part, and variations in the film thickness of the semiconductor layer cause a decrease in productivity and variations in characteristics between solar cell elements. There was a problem of inviting. In addition, junction breakdown between the semiconductor layer and the electrode, current leakage, ohmic cross, and the like may occur, causing a decrease in electrical output.

  In order to overcome such problems, a light confinement technique using a flat shape without physical irregularities has been proposed. For example, in Patent Document 1, light confinement is realized by providing an irregular reflection layer made of a thin film in which regions having different refractive indexes are distributed between an electrode and a semiconductor layer using patterning and ion implantation.

JP-A-7-202231

  However, according to the technique of Patent Document 1, a resist coating process, a photolithography process patterning process, an ion implantation process, a resist removal process, and a heat treatment process are performed as manufacturing processes. As a processing apparatus used in each of these steps, there is a problem that, unlike a fine semiconductor element, a large product is required in the manufacturing process of a large product such as a solar cell, which increases equipment costs. . Further, in the patterning process and the resist removal process, there is a problem that a large amount of industrial waste liquid is generated and the environmental load is large.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an inexpensive photovoltaic device having a low environmental load in manufacturing and excellent in productivity and photoelectric conversion efficiency, and a manufacturing method thereof.

  In order to solve the above-described problems and achieve the object, a photovoltaic device according to the present invention includes a first electrode layer, a photoelectric conversion layer that performs photoelectric conversion, and a second electrode layer on a substrate, The electrode layer on the light incident side of the first electrode layer or the second electrode layer has a flat surface and a diffuse reflection region that has a refractive index locally different from that of the electrode layer and diffusely reflects light. It is an electrode layer.

  According to the present invention, there is an effect that an inexpensive photovoltaic device having a low environmental load in production and excellent in productivity and photoelectric conversion efficiency can be obtained.

FIG. 1 is a cross-sectional view showing a configuration of a thin-film solar cell that is a super straight type photovoltaic element according to the first embodiment of the present invention. FIG. 2-1 is a cross-sectional view for explaining an example of a manufacturing process of the thin-film solar cell according to the first embodiment. 2-2 is sectional drawing for demonstrating an example of the manufacturing process of the thin film solar cell concerning Embodiment 1. FIGS. FIGS. 2-3 is sectional drawing for demonstrating an example of the manufacturing process of the thin film solar cell concerning Embodiment 1. FIGS. 2-4 is sectional drawing for demonstrating an example of the manufacturing process of the thin film solar cell concerning Embodiment 1. FIGS. 2-5 is sectional drawing for demonstrating an example of the manufacturing process of the thin film solar cell concerning Embodiment 1. FIGS. FIG. 3 is a flowchart for explaining an example of the manufacturing process of the thin-film solar cell according to the first embodiment of the present invention. FIG. 4 is a plan view showing an example of a laser irradiation position in the plane of the diffusion source layer according to the first embodiment of the present invention. FIG. 5: is sectional drawing which shows the structure of the super straight type thin film solar cell concerning Embodiment 2 of this invention. FIG. 6 is a cross-sectional view showing a configuration of a substrate-type thin film solar cell according to the third embodiment of the present invention. FIG. 7: is sectional drawing which shows the structure of the substrate type thin film solar cell concerning Embodiment 4 of this invention. FIG. 8: is sectional drawing which shows the structure of the super straight type thin film solar cell concerning Embodiment 5 of this invention. FIG. 9 is a plan view showing the arrangement of laser irradiation positions in the plane of the diffusion source layer according to the fifth embodiment. FIG. 10 is a plan view showing an example of the laser irradiation position of the first periodic arrangement in the plane of the diffusion source layer according to the fifth embodiment of the present invention. FIG. 11 is a plan view showing an example of laser irradiation positions of the second periodic arrangement in the plane of the diffusion source layer according to the fifth embodiment of the present invention. FIG. 12 is a plan view illustrating an example of a third laser-arranged laser irradiation position in the plane of the diffusion source layer according to the fifth embodiment of the present invention.

  Embodiments of a photovoltaic device and a method for manufacturing the photovoltaic device according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings. Further, even a plan view may be hatched to make the drawing easy to see.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a configuration of a thin-film solar cell that is a super straight type photovoltaic element according to the first embodiment of the present invention. The thin film solar cell according to the first embodiment includes a lower transparent electrode layer (first electrode layer) 2, a semiconductor photoelectric conversion layer 4, and an upper transparent electrode layer in which irregular reflection regions 3 are distributed on a translucent substrate 1. (Second electrode layer) 5 and metal reflection layer 6 are sequentially laminated. In this thin film solar cell, light is incident from the substrate 1 side.

  As the light-transmitting substrate 1, a glass substrate, a light-transmitting resin having heat resistance such as polyimide or polyvinyl, or a laminate thereof can be used as appropriate. There is no particular limitation as long as the whole can be structurally supported. Further, a metal film with high permeability, a transparent conductive film, or an insulating film may be formed on these surfaces.

The lower transparent electrode layer 2 and the upper transparent electrode layer 5 are made of a light-transmitting conductive material. For example, tin oxide (SnO ₂ ), zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), lead oxide (PbO ₂ ), Cadmium oxide (CdO) or the like can be used. However, since lead oxide (PbO ₂ ) and cadmium oxide (CdO) are toxic, it is preferable to use tin oxide (SnO ₂ ), zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), or the like. A trace amount of impurities may be added to the lower transparent electrode layer 2 and the upper transparent electrode layer 5. The lower transparent electrode layer 2 and the upper transparent electrode layer 5 may be a laminated film of these materials.

The irregular reflection region 3 is provided locally distributed in the lower transparent electrode layer 2 by a material having a refractive index different from that of the lower transparent electrode layer 2 and diffuses incident light. For example, when the constituent material of the lower transparent electrode layer 2 is zinc oxide (ZnO), aluminum (Al) -doped zinc oxide (ZnAlO) is used as the constituent material of the irregular reflection region 3. As the constituent material of the irregular reflection region 3, for example, when the constituent material of the lower transparent electrode layer 2 is tin oxide (SnO ₂ ), antimony-doped tin oxide (SnSbO), SnFO, or SnBO can be used. As the constituent material of the irregular reflection region 3, for example, ITO (InSnO) can be used when the constituent material of the lower transparent electrode layer 2 is indium oxide (In ₂ O ₃ ). Further, as the constituent material of the irregular reflection region 3, for example, when the constituent material of the lower transparent electrode layer 2 is lead oxide (PbO ₂ ), PbBiO can be used. The constituent material of the irregular reflection region 3 can be CdInO when the constituent material of the lower transparent electrode layer 2 is cadmium oxide (CdO).

  The semiconductor photoelectric conversion layer 4 has at least one pair of pn junctions or pin junctions, and is a semiconductor layer configured by laminating one or more thin film semiconductor layers that generate power by generating incident light and generate photovoltaic power. is there. The semiconductor photoelectric conversion layer 4 includes, for example, a p-type semiconductor layer that is a first conductive semiconductor layer, an i-type semiconductor layer that is an intrinsic semiconductor layer, and a second conductive semiconductor in order from the light-receiving surface side (translucent substrate 1 side). Each semiconductor layer is an n-type semiconductor layer.

  The metal reflective layer 6 is made of light such as aluminum (Al), silver (Ag), copper (Cu), chromium (Cr), gold (Au), magnesium (Mg), indium (In), titanium (Ti), etc. It is a reflective layer made of a material capable of reflecting.

  Each layer of the lower transparent electrode layer 2, the semiconductor photoelectric conversion layer 4, the upper transparent electrode layer 5, and the metal reflective layer 6 described above can be manufactured by a known method such as a CVD (Chemical Vapor Deposition) method, a sputtering method, or a vapor deposition method. .

  The thin film solar cell according to the first embodiment as described above has the irregular reflection region 3 provided locally distributed in the lower transparent electrode layer 2 by a material having a refractive index different from that of the lower transparent electrode layer 2. By having such an irregular reflection region 3, in the thin film solar cell according to the first embodiment, the light incident from the substrate 1 side is irregularly reflected to extend the substantial optical path length in the semiconductor photoelectric conversion layer 4. The amount of light absorption can be increased and the photoelectric conversion efficiency can be improved.

  Further, since the surface of the irregular reflection region 3 and the lower transparent electrode layer 2 on which the irregular reflection region 3 is formed is flat, the occurrence of defects in the semiconductor photoelectric conversion layer 4 due to physical unevenness, There is no variation in film thickness, and there is no decrease in productivity, variation in characteristics between solar cell elements, or degradation in solar cell element characteristics.

  Further, since the irregular reflection region 3 is formed inside the lower transparent electrode layer 2, the number of layers involved in light confinement can be reduced by one as compared with the technique of Patent Document 1, and the manufacturing process can be shortened and the manufacturing cost can be reduced. Excellent.

  Therefore, according to the thin film solar cell according to the first embodiment, a super straight type thin film solar cell excellent in photoelectric conversion efficiency is realized.

  Below, the manufacturing method of the thin film solar cell concerning Embodiment 1 comprised as mentioned above is demonstrated. FIGS. 2-1 to 2-5 are cross-sectional views for explaining an example of the manufacturing process of the thin-film solar cell according to the first embodiment. FIG. 3 is a flowchart for explaining an example of the manufacturing process of the thin-film solar cell according to the first embodiment. Below, the case where the lower transparent electrode layer 2 and the upper transparent electrode layer 5 are formed of zinc oxide (ZnO) and the irregular reflection region 3 is formed of aluminum (Al) -doped zinc oxide (ZnAlO) will be described as an example.

  First, the lower transparent electrode layer 2 made of zinc oxide (ZnO) is formed on the translucent substrate 1 (FIG. 2-1, step S1). For example, a glass substrate is used as the translucent substrate 1. Further, as the lower transparent electrode layer 2, zinc oxide (ZnO) having a thickness of 1 μm is formed by, for example, a CVD method.

  Next, a diffusion source layer 7 made of, for example, 100 nm thick aluminum (Al) is formed on the lower transparent electrode layer 2 by a known method such as a sputtering method (FIG. 2-2, step S2). Next, the diffuse reflection region 3 made of ZnAlO having a refractive index different from that of ZnO is locally formed in the lower transparent electrode layer 2 by locally irradiating the laser L on the diffusion source layer 7 (FIG. 2). -3, step S3). By irradiating the diffusion source layer 7 with the laser L, only the laser irradiation position 10 is locally heated in the diffusion source layer 7, and aluminum (Al) is diffused from the diffusion source layer 7 into the lower transparent electrode layer 2. . Thereby, as shown in FIG. 2-3, the irregular reflection region 3 made of aluminum (Al) -doped zinc oxide (ZnAlO) is locally formed in the film of the lower transparent electrode layer 2. Here, even after the irregular reflection region 3 is formed, the surface of the lower transparent electrode layer 2 is kept flat.

  FIG. 4 is a plan view showing an example of the laser irradiation position 10 in the plane of the diffusion source layer 7. Although FIG. 4 is a plan view, the laser irradiation position 10 is hatched for easy understanding. In the present embodiment, the laser irradiation positions 10 are arranged with a period of 1.5 μm, but may be arranged with other dimensions. As the wavelength of the laser L, it is preferable to select an absorption wavelength of the material of the lower transparent electrode layer 2 or the material of the diffusion source layer 7. Thereby, the laser irradiation position 10 can be efficiently heated locally. In the present embodiment, 900 nm that is the absorption wavelength of the diffusion source layer 7 is selected as the wavelength of the laser L.

  Next, the diffusion source layer 7 is removed by etching (FIG. 2-4, step S4). In the present embodiment, only the diffusion source layer 7 made of aluminum (Al) is removed by etching by wet etching using a sodium hydroxide (NaOH) aqueous solution. Etching is not limited to wet etching, and dry etching may be used.

  Next, the semiconductor photoelectric conversion layer 4 made of, for example, amorphous silicon is formed by a plasma CVD method (FIG. 2-5, step S5). As the semiconductor photoelectric conversion layer 4, from the lower transparent electrode layer 2 side, a p-type amorphous silicon film (a-Si film), an i-type amorphous silicon film (a-Si film), an n-type amorphous silicon film (a -Si film) are sequentially stacked.

  Next, the upper transparent electrode layer 5 made of, for example, zinc oxide (ZnO) is formed by, for example, the CVD method (FIG. 2-5, step S6). Next, the metal reflective layer 6 made of, for example, silver (Ag) is formed by a sputtering method (FIG. 2-5, step S7). By performing the above steps, the super straight type thin film solar cell according to the first embodiment shown in FIG. 1 is obtained.

  In the method for manufacturing the thin-film solar cell according to the first embodiment as described above, the irregular reflection region 3 made of a material having a refractive index different from that of the lower transparent electrode layer 2 is locally distributed in the lower transparent electrode layer 2. Form. By forming such an irregular reflection region 3, light incident from the substrate 1 side is diffusely reflected to extend the substantial optical path length in the semiconductor photoelectric conversion layer 4, thereby increasing the amount of light absorption and photoelectric conversion efficiency. Can be improved.

  Further, since the surface of the irregular reflection region 3 and the lower transparent electrode layer 2 on which the irregular reflection region 3 is formed is flat, the occurrence of defects in the semiconductor photoelectric conversion layer 4 due to physical unevenness, There is no variation in film thickness, and there is no decrease in productivity, variation in characteristics between solar cell elements, or degradation in solar cell element characteristics.

  Moreover, in the manufacturing method of the thin film solar cell concerning Embodiment 1, after forming the diffusion source layer 7 on the lower transparent electrode layer 2, the irregular reflection area | region 3 is formed by performing laser irradiation. For this reason, since a large-scale installation is unnecessary and an installation cost is suppressed, a thin film solar cell can be manufactured at low cost. In addition, since no industrial waste liquid is generated, the environmental load is small.

  Further, since the irregular reflection region 3 is formed inside the lower transparent electrode layer 2, the number of layers involved in light confinement can be reduced by one as compared with the technique of Patent Document 1, and the manufacturing process is shortened and the manufacturing cost is excellent. .

  Therefore, according to the manufacturing method of the thin film solar cell concerning Embodiment 1, the super straight type thin film solar cell excellent in photoelectric conversion efficiency can be produced cheaply, suppressing environmental load.

Embodiment 2. FIG.
FIG. 5: is sectional drawing which shows the structure of the super straight type thin film solar cell concerning Embodiment 2 of this invention. In FIG. 5, members similar to those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 5, the super straight type thin film solar cell according to the second embodiment includes a lower transparent electrode layer (first electrode layer) 2 in which irregular reflection regions 3 are distributed on a translucent substrate 1. The semiconductor photoelectric conversion layer 4, the upper transparent electrode layer (second electrode layer) 5 in which the irregular reflection region 8 is distributed, and the metal reflection layer 6 are sequentially laminated. In this thin film solar cell, light is incident from the substrate 1 side.

The irregular reflection region 8 is locally distributed in the upper transparent electrode layer 5 by a material having a refractive index different from that of the upper transparent electrode layer 5 and diffuses incident light. For example, when the constituent material of the upper transparent electrode layer 5 is zinc oxide (ZnO), aluminum (Al) -doped zinc oxide (ZnAlO) is used as the constituent material of the irregular reflection region 8. For example, when the constituent material of the upper transparent electrode layer 5 is tin oxide (SnO ₂ ), antimony-doped tin oxide (SnSbO), SnFO, or SnBO can be used as the constituent material of the irregular reflection region 8. As the constituent material of the irregular reflection region 8, for example, ITO (InSnO) can be used when the constituent material of the upper transparent electrode layer 5 is indium oxide (In ₂ O ₃ ). Further, as the constituent material of the irregular reflection region 8, for example, when the constituent material of the upper transparent electrode layer 5 is lead oxide (PbO ₂ ), PbBiO can be used. In addition, as the constituent material of the irregular reflection region 8, CdInO can be used when the constituent material of the upper transparent electrode layer 5 is cadmium oxide (CdO).

  The super-straight type thin film solar cell according to the second embodiment configured as described above is an irregular reflection region after the upper transparent electrode layer 5 is formed in the method for manufacturing a super straight-type thin film solar cell according to the first embodiment. In the same manner as in the manufacturing method 3, the irregular reflection region 8 is obtained by being distributed inside the upper transparent electrode layer 5.

  According to the second embodiment as described above, as in the superstrate type thin film solar cell according to the first embodiment, a material having a refractive index different from that of the lower transparent electrode layer 2 is locally used in the lower transparent electrode layer 2. The diffused reflection region 3 is provided in a distributed manner. By having such an irregular reflection region 3, in the thin film solar cell according to the first embodiment, the light incident from the substrate 1 side is irregularly reflected to extend the substantial optical path length in the semiconductor photoelectric conversion layer 4. The amount of light absorption can be increased and the photoelectric conversion efficiency can be improved.

  Further, according to the second embodiment, the irregular reflection region 8 is provided which is locally distributed in the upper transparent electrode layer 5 by using a material having a refractive index different from that of the upper transparent electrode layer 5. By having such an irregular reflection region 8, in the thin film solar cell according to the second embodiment, the light that has passed through the semiconductor photoelectric conversion layer 4 is irregularly reflected and returned to the semiconductor photoelectric conversion layer 4 again. Thereby, light absorption amount can be increased by extending the substantial optical path length in the semiconductor photoelectric converting layer 4 of the light which reentered into the semiconductor photoelectric converting layer 4, and photoelectric conversion efficiency can be improved more.

  Further, similarly to the superstrate type thin film solar cell according to the first embodiment, the irregular reflection region 3 and the surface of the lower transparent electrode layer 2 on which the irregular reflection region 3 is formed are flat, resulting in physical unevenness. The occurrence of defects in the semiconductor photoelectric conversion layer 4 and the variation in film thickness of the semiconductor photoelectric conversion layer 4 do not occur, and the productivity, the variation in characteristics between solar cell elements, and the decrease in solar cell element characteristics do not occur.

  In addition, the irregular reflection region 8 is formed after the semiconductor photoelectric conversion layer 4 is formed, and the irregular reflection region 8 and the surface of the upper transparent electrode layer 5 on which the irregular reflection region 8 is formed are flat. The occurrence of defects in the semiconductor photoelectric conversion layer 4 and the variation in film thickness of the semiconductor photoelectric conversion layer 4 do not occur, and the productivity, the variation in characteristics between solar cell elements, and the decrease in solar cell element characteristics do not occur.

  Therefore, according to the second embodiment, it is possible to obtain a super straight-type thin-film solar cell with more excellent photoelectric conversion efficiency at a low cost while suppressing the environmental load.

Embodiment 3 FIG.
FIG. 6 is a cross-sectional view showing a configuration of a substrate-type thin film solar cell according to the third embodiment of the present invention. In FIG. 6, members similar to those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 6, the substrate-type thin film solar cell according to the third embodiment has a metal reflective layer 6, a lower transparent electrode layer (first electrode layer) 2, a semiconductor photoelectric conversion layer 4, on a substrate 9. The upper transparent electrode layer (second electrode layer) 5 having the irregular reflection region 8 distributed therein is sequentially laminated. In this thin film solar cell, light is incident from the upper transparent electrode layer 5 side.

  The material of the substrate 9 is not particularly limited as long as it is solid, but for example, metal, semiconductor, glass, ceramics and the like are preferable. The substrate-type thin film solar cell according to the third embodiment sequentially forms the metal reflection layer 6, the lower transparent electrode layer 2, the semiconductor photoelectric conversion layer 4, the upper transparent electrode layer 5, and the irregular reflection region 8 on the substrate 9. Can be obtained. Since the manufacturing method of each layer is the same as that of Embodiment 1 and Embodiment 2, it is omitted here with reference to the above description.

  According to the third embodiment as described above, the irregular reflection region 8 is provided that is locally distributed in the upper transparent electrode layer 5 by using a material having a refractive index different from that of the upper transparent electrode layer 5. By having such an irregular reflection region 8, in the thin film solar cell according to the third embodiment, the light incident from the upper transparent electrode layer 5 side is irregularly reflected so that the substantial optical path length in the semiconductor photoelectric conversion layer 4 is increased. By extending, the amount of light absorption can be increased and the photoelectric conversion efficiency can be improved.

  In addition, the irregular reflection region 8 is formed after the semiconductor photoelectric conversion layer 4 is formed, and the irregular reflection region 8 and the surface of the upper transparent electrode layer 5 on which the irregular reflection region 8 is formed are flat. The occurrence of defects in the semiconductor photoelectric conversion layer 4 and the variation in film thickness of the semiconductor photoelectric conversion layer 4 do not occur, and the productivity, the variation in characteristics between solar cell elements, and the decrease in solar cell element characteristics do not occur.

  Further, since the irregular reflection region 8 is formed inside the upper transparent electrode layer 5, the number of layers involved in light confinement can be reduced by one as compared with the technique of Patent Document 1, and the manufacturing process can be shortened and the manufacturing cost can be reduced. Excellent.

  Therefore, according to Embodiment 3, a substrate-type thin film solar cell having excellent photoelectric conversion efficiency can be obtained at a low cost while suppressing environmental load.

Embodiment 4 FIG.
FIG. 7: is sectional drawing which shows the structure of the substrate type thin film solar cell concerning Embodiment 4 of this invention. In FIG. 7, members similar to those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 7, the substrate-type thin film solar cell according to the fourth embodiment includes a metal transparent layer 6, a lower transparent electrode layer 2 in which irregular reflection regions 3 are distributed, a semiconductor photoelectric conversion layer on a substrate 9. 4. The upper transparent electrode layer 5 in which the irregular reflection region 8 is distributed inside is sequentially laminated. In this thin film solar cell, light is incident from the upper transparent electrode layer 5 side.

  The material of the substrate 9 is not particularly limited as long as it is solid, but for example, metal, semiconductor, glass, ceramics and the like are preferable. The substrate-type thin film solar cell according to the fourth embodiment includes a metal reflective layer 6, a lower transparent electrode layer 2, an irregular reflection region 3, a semiconductor photoelectric conversion layer 4, an upper transparent electrode layer 5, and an irregular reflection region on a substrate 9. It is obtained by forming 8 sequentially. Since the manufacturing method of each layer is the same as that of Embodiment 1 and Embodiment 2, it is omitted here with reference to the above description.

  According to the fourth embodiment as described above, as in the substrate-type thin film solar cell according to the first embodiment, a material having a refractive index different from that of the upper transparent electrode layer 5 is locally formed in the upper transparent electrode layer 5. The diffused reflection region 8 is provided in a distributed manner. By having such an irregular reflection region 8, in the thin-film solar cell according to the fourth embodiment, the light incident from the upper transparent electrode layer 5 side is irregularly reflected so that the substantial optical path length in the semiconductor photoelectric conversion layer 4 is increased. By extending, the amount of light absorption can be increased and the photoelectric conversion efficiency can be improved.

  According to the fourth embodiment as described above, the irregular reflection region 3 provided locally distributed in the lower transparent electrode layer 2 by the material having a refractive index different from that of the lower transparent electrode layer 2 is provided. By having such an irregular reflection region 3, in the thin-film solar cell according to the fourth embodiment, light that has passed through the semiconductor photoelectric conversion layer 4 is irregularly reflected and returned to the semiconductor photoelectric conversion layer 4 again. Thereby, light absorption amount can be increased by extending the substantial optical path length in the semiconductor photoelectric converting layer 4 of the light which reentered into the semiconductor photoelectric converting layer 4, and photoelectric conversion efficiency can be improved more.

  In addition, the irregular reflection region 8 is formed after the semiconductor photoelectric conversion layer 4 is formed, and the irregular reflection region 8 and the surface of the upper transparent electrode layer 5 on which the irregular reflection region 8 is formed are flat. The occurrence of defects in the semiconductor photoelectric conversion layer 4 and the variation in film thickness of the semiconductor photoelectric conversion layer 4 do not occur, and the productivity, the variation in characteristics between solar cell elements, and the decrease in solar cell element characteristics do not occur.

  Further, since the surface of the irregular reflection region 3 and the lower transparent electrode layer 2 on which the irregular reflection region 3 is formed is flat, the occurrence of defects in the semiconductor photoelectric conversion layer 4 due to physical unevenness, There is no variation in film thickness, and there is no decrease in productivity, variation in characteristics between solar cell elements, or degradation in solar cell element characteristics.

  Therefore, according to Embodiment 4, it is possible to obtain a substrate-type thin film solar cell with more excellent photoelectric conversion efficiency at low cost while suppressing environmental load.

Embodiment 5 FIG.
FIG. 8: is sectional drawing which shows the structure of the super straight type thin film solar cell concerning Embodiment 5 of this invention. The basic configuration of the thin film solar cell according to the fifth embodiment is the same as that of the super straight type thin film solar cell according to the first embodiment. The thin film solar cell according to the fifth embodiment is different from the thin film solar cell according to the first embodiment in that the irregular reflection region 3 is formed by laser irradiation at a laser irradiation position where a plurality of periods are overlapped. . That is, the irregular reflection region 3 according to the fifth embodiment is formed at a position where a plurality of periods are overlapped in the plane of the lower transparent electrode layer 2.

  In the first embodiment, as shown in FIG. 4, the irregular reflection region 3 is formed by performing laser irradiation with the arrangement of the laser irradiation positions 10 having a single period. On the other hand, in the fifth embodiment, as shown in FIG. 9, the irregular reflection region 3, the second irregular reflection region 11, and the second irregular reflection region (not shown) are obtained by laser irradiation at the laser irradiation position where a plurality of periods are overlapped. ) Is formed. FIG. 9 is a plan view showing the arrangement of laser irradiation positions in the plane of the diffusion source layer 7 when forming the irregular reflection region 3 in the thin film solar cell according to the fifth embodiment.

  The arrangement of laser irradiation positions shown in FIG. 9 is an arrangement in which arrangements of laser irradiation positions with three different periods are overlapped. FIG. 10 is a plan view showing an example of the first laser irradiation position 12 a in the periodic arrangement in the plane of the diffusion source layer 7. FIG. 11 is a plan view showing an example of the second laser irradiation position 12 b in the periodic arrangement in the plane of the diffusion source layer 7. FIG. 12 is a plan view showing an example of the third laser irradiation position 12 c in the periodic arrangement in the plane of the diffusion source layer 7. 10 to 12 are plan views, but the laser irradiation positions are hatched for easy understanding.

  The laser irradiation positions 12a of the first cycle are arranged at a cycle of 0.4 μm as shown in FIG. The laser irradiation positions 12b of the second period are arranged at a period of 0.6 μm as shown in FIG. The laser irradiation positions 12c of the third cycle are arranged at a cycle of 1.3 μm as shown in FIG. The thin film solar cell according to the fifth embodiment can be obtained by changing the arrangement of the laser irradiation positions 10 to the arrangement shown in FIG. 9 in the method for manufacturing the thin film solar cell described in the first embodiment.

  Thus, the arrangement of the laser irradiation positions 10 does not have to be a single period, and the laser irradiation may be performed with an arrangement in which a plurality of periods are overlapped. The actual optimum arrangement of the laser irradiation positions is the period of the wavelength band in the spectral sensitivity region of the semiconductor photoelectric conversion layer 4. Further, in the case of a tandem-type thin film solar cell in which a plurality of semiconductor photoelectric conversion layers 4 are provided, photoelectric conversion efficiency is obtained by superimposing periods in accordance with the wavelength bands of the spectral sensitivity regions of the respective semiconductor photoelectric conversion layer layers. Can be obtained.

  As described above, the photovoltaic device according to the present invention is useful for efficiently and inexpensively producing a photovoltaic device excellent in photoelectric conversion efficiency while suppressing an environmental load in production.

DESCRIPTION OF SYMBOLS 1 Translucent board | substrate 2 Lower transparent electrode layer 3 Diffuse reflection area | region 4 Semiconductor photoelectric converting layer 5 Upper transparent electrode layer 6 Metal reflective layer 7 Diffusion source layer 8 Diffuse reflection area | region 9 Substrate 10 Laser irradiation position 11 2nd diffuse reflection area | region 12a 1 Laser irradiation position 12b in the periodic arrangement Laser irradiation position in the second periodic arrangement 12c Laser irradiation position in the third periodic arrangement L Laser

Claims (14)

Having a photoelectric conversion layer and a second electrode layer for performing photoelectric conversion on the substrate;
Of the first electrode layer or the second electrode layer, the electrode layer on the light incident side has a flat surface and an irregular reflection region in the film that has a refractive index different from that of the electrode layer and diffuses light. A transparent electrode layer,
A photovoltaic device characterized by the above. The first electrode layer is the transparent electrode layer;
The substrate has translucency;
Having a super straight type structure in which light is incident from the substrate side;
The photovoltaic element according to claim 1. The second electrode layer is the transparent electrode layer;
The substrate has translucency;
A reflective layer for reflecting light on the second electrode layer;
Having a super straight type structure in which light is incident from the substrate side;
The photovoltaic element according to claim 1. The second electrode layer is the transparent electrode layer;
Having a substrate type structure in which light is incident from the second electrode layer side;
The photovoltaic element according to claim 1. The first electrode layer is the transparent electrode layer;
A reflective layer for reflecting light on the substrate side of the first electrode layer;
Having a substrate type structure in which light is incident from the second electrode layer side;
The photovoltaic element according to claim 1. The irregular reflection regions are arranged at regular intervals in the plane of the transparent electrode layer;
The photovoltaic element according to claim 1. The irregular reflection regions are arranged at intervals in which a plurality of different constant periods are overlapped in the plane of the transparent electrode layer,
The photovoltaic element according to claim 1. The interval of the constant period is a value included in the wavelength band of the spectral sensitivity region of the photoelectric conversion layer,
The photovoltaic element according to claim 6 or 7, wherein: A plurality of the photoelectric conversion layers are provided,
The plurality of different constant periods are values included in wavelength bands of spectral sensitivity regions of the photoelectric conversion layers different from each other,
The photovoltaic element according to claim 7. In the method for manufacturing a photovoltaic device, including a step of forming a first electrode layer, a photoelectric conversion layer that performs photoelectric conversion, and a second electrode layer on a substrate,
Forming the electrode layer on the light incident side of the first electrode layer or the second electrode layer,
Forming a transparent conductive film;
Forming a diffusion source layer on the transparent conductive film;
By locally heating the diffusion source layer by laser irradiation and diffusing the elements of the diffusion source layer into the transparent conductive film, a diffuse reflection region having a refractive index different from that of the transparent conductive film and irregularly reflecting light is formed. Forming locally in the transparent conductive film;
A method for producing a photovoltaic device comprising: Disposing the irregular reflection regions at regular intervals in the plane of the transparent electrode layer;
The method for producing a photovoltaic element according to claim 10. Disposing the irregular reflection regions at intervals in which a plurality of different constant periods are overlapped in the plane of the transparent electrode layer;
The method for producing a photovoltaic element according to claim 10. The interval of the constant period is a value included in the wavelength band of the spectral sensitivity region of the photoelectric conversion layer,
The method for producing a photovoltaic element according to claim 11 or 12, wherein: Forming a plurality of the photoelectric conversion layers;
The plurality of different constant periods are values included in wavelength bands of spectral sensitivity regions of the photoelectric conversion layers different from each other,
The method for producing a photovoltaic element according to claim 12.

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