JPWO2010067702A1 - Thin film solar cell and manufacturing method thereof - Google Patents

Abstract

In the method for manufacturing a thin-film solar cell according to an embodiment of the present invention, a film made of a conductive material is formed on a substrate, and the first electrode layer of each cell is patterned by separating the cells. A first photoelectric conversion layer is formed on the substrate on which the first electrode layer is formed, and the first photoelectric conversion layer is separated for each cell. A groove is formed, a second photoelectric conversion layer is formed on the substrate on which the first photoelectric conversion layer is formed, and the second photoelectric conversion layer is formed within the first groove formation position. Separated by a second groove having a second width smaller than the first width, a second electrode layer is formed on the second photoelectric conversion layer and on the side and bottom surfaces of the groove.

Description

  The present invention relates to a thin film solar cell having a laminated structure including a plurality of photoelectric conversion layers having different band gaps, and a method for manufacturing the same.

The solar power generation system is expected as clean energy that protects the global environment in the 21st century from the increase in CO ₂ gas due to the burning of fossil energy, and its production volume is increasing explosively around the world. For this reason, the situation where the silicon wafer runs short all over the world has occurred. Therefore, in recent years, the production amount of thin-film solar cells in which a photoelectric conversion layer (semiconductor layer) that is not rate-controlled by the supply amount of silicon wafers is a thin film is increasing rapidly.

  Conventionally, thin-film solar cells have been proposed to have a tandem structure in which a plurality of photoelectric conversion layers made of materials having different band gaps are stacked on an insulating translucent substrate in order to effectively use the solar spectrum widely (for example, , See Patent Document 1). This tandem thin film solar cell includes a surface electrode layer made of a transparent conductive material on a translucent substrate, an amorphous silicon film having a pin structure, and a microcrystalline silicon film having a pin structure. A plurality of cells in which a photoelectric conversion layer made of a laminated film or the like and a back electrode layer such as Ag are sequentially laminated have a structure connected in series in one direction. Here, the surface electrode layer is formed to be separated from the surface electrode layer of the adjacent cell by the first separation groove and partially overlap with one of the adjacent photoelectric conversion layers. Further, the photoelectric conversion layer and the back electrode layer are separated from the photoelectric conversion layer and the back electrode layer of the adjacent cell by the second separation groove, and are partially overlapped with the other adjacent surface electrode layer. . And a back surface electrode layer is connected with the surface electrode layer of the other adjacent cell which overlaps partially through the connection groove | channel formed through the photoelectric converting layer.

JP 2005-45129 A

  As described above, in order to generate a sufficient current to function as a solar cell using a microcrystalline material for a part of the photoelectric conversion layer, a film thickness of several μm is generally required. For example, when a microcrystalline silicon film is used as a part of the photoelectric conversion layer, a film thickness of about 2 μm is required, and when a microcrystalline silicon germanium film is used, a film thickness of about 1 μm is required. Therefore, when a thin film solar cell having a tandem structure in which several layers of these microcrystalline materials are stacked, the total film thickness of the photoelectric conversion layer becomes several μm or more.

  Moreover, in the modularization process of a thin film solar cell, after separating the photoelectric conversion layer laminated | stacked on the surface electrode layer (transparent electrode) into the strip-shaped unit cell by the laser scribing method, a back surface electrode layer is formed and it adjoins. By connecting the front electrode layer and the back electrode layer of the unit cell, a thin film solar cell module in which the unit cells are connected in series is formed. Here, in the case of the tandem structure described in Patent Document 1, a back electrode layer (silver thin film) is formed on the side surface of the step having a height of several μm at the end of the unit cell after separation. The back electrode layer is often formed by sputtering, and in this case, there is a concern that the coverage will be insufficient on the side surface of the step. In fact, when a back electrode layer having a sufficient thickness is not formed on the side surface of the cell, there is a problem that the series resistance component of the module increases and the power generation efficiency decreases.

  In the method for manufacturing a thin film solar cell having a tandem structure described in Patent Document 1, the back electrode film on the side surface of the cell is increased by increasing the film formation time of the back electrode layer in order to suppress the increase in the series resistance component. We are trying to solve the lack of coverage by using thick film. However, increasing the film formation time has a problem in that the production throughput is lowered and the manufacturing cost is increased.

  The present invention has been made in view of the above, and in a thin film solar cell having a tandem structure, lack of coverage is not a problem on the step side surface of the separation groove formed between adjacent cells, and the film thickness is thinner than the conventional one. An object of the present invention is to obtain a thin film solar cell having a back electrode layer and a manufacturing method thereof.

  In order to achieve the above object, a method of manufacturing a thin-film solar cell according to the present invention includes forming a film made of a conductive material on a substrate, and patterning the cells so as to separate the cells, so that the first of each cell is formed. A first electrode layer forming step of forming a first photoelectric conversion layer, a first photoelectric conversion layer forming step of forming a first photoelectric conversion layer on the substrate on which the first electrode layer is formed, and the first A first groove forming step for forming a first groove having a first width for separating one photoelectric conversion layer for each cell; and a second groove formed on the substrate on which the first photoelectric conversion layer is formed. A second photoelectric conversion layer forming step of forming a photoelectric conversion layer; and a second photoelectric conversion layer having a second width that is narrower than the first width within the formation position of the first groove. A second groove forming step for separating the first groove, the second photoelectric conversion layer, the side surface and the bottom surface of the groove, Characterized in that it comprises a second electrode layer forming step of forming an electrode layer.

  According to this invention, the cross-sectional structure on the side where the groove of the photoelectric conversion laminate is formed is formed so as to cover the side surface on the adjacent cell side of the lower photoelectric conversion layer with the upper photoelectric conversion layer. The cross-sectional shape is a gentle step or slope. Accordingly, when the back electrode layer is formed by a film forming method such as sputtering, it is easy to obtain good coverage on the cell side surface in the groove even in a thin film. As a result, the time required for forming the back electrode layer is significantly shortened compared to the conventional case, and the production throughput can be improved. Moreover, since the series resistance component after modularization can be reduced and the Joule loss in the back electrode layer can be reduced, the power generation efficiency of the thin-film solar cell is expected to be improved.

1 is a cross-sectional view schematically showing an example of the structure of a thin-film solar cell according to Embodiment 1 of the present invention. FIGS. 2-1 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 1). 2-2 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 2). FIGS. 2-3 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 3). 2-4 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 4). 2-5 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 5). 2-6 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 6). 2-7 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 7). FIGS. 2-8 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 8). 2-9 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 9). FIGS. 2-10 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 1 of this invention (the 10). FIG. 3 is a cross-sectional view schematically showing an example of the structure of the thin-film solar cell according to Embodiment 2 of the present invention. FIGS. 4-1 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 2 of this invention (the 1). 4-2 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 2 of this invention (the 2). 4-3 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 2 of this invention (the 3). 4-4 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 2 of this invention (the 4). 4-5 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 2 of this invention (the 5). 4-6 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 2 of this invention (the 6). 4-7 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 2 of this invention (the 7). 4-8 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 2 of this invention (the 8). 4-9 is sectional drawing which shows typically an example of the manufacturing method of the thin film solar cell by Embodiment 2 of this invention (the 9).

  Embodiments of a thin-film solar cell and a method for manufacturing the same according to the present invention will be described below in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments. Moreover, the cross-sectional views of the thin film solar cell used in the following embodiments are schematic, and the relationship between the thickness and width of the layers, the ratio of the thicknesses of the layers, and the like are different from the actual ones.

Embodiment 1 FIG.
1 is a cross-sectional view schematically showing an example of the structure of a thin-film solar cell according to Embodiment 1 of the present invention. In this thin-film solar cell 1, a plurality of cells 10 (10-1 to 10-4) are predetermined on an insulating light-transmitting substrate 2 such as a light-transmitting glass substrate or a light-transmitting organic film material such as polyimide. They are connected in series in the direction (left and right direction in the figure). Each cell 10 includes a surface electrode layer 11 (11-1 to 11-4), a first photoelectric conversion layer 13, a second photoelectric conversion layer 15, a third photoelectric conversion layer 17, and a back electrode layer 19. It is formed by photoelectric conversion elements stacked in order. Here, a stacked body of the first to third photoelectric conversion layers 13, 15, 17 of one cell 10, and a stacked body of the first to third photoelectric conversion layers 13, 15, 17 of the adjacent cell 10, A separation groove 21 is formed between them, and a region on the insulating translucent substrate 2 surrounded by the separation groove 21 is referred to as a cell formation region R. Moreover, in this thin film solar cell 1, the surface on the light incident side (insulating translucent substrate 2 side) is referred to as a front surface, and the surface opposite to the front surface is referred to as a back surface.

  The surface electrode layer 11 is made of a transparent conductive oxide material such as tin oxide, zinc oxide, ITO (Indium Tin Oxide), or a material obtained by adding a metal to these transparent conductive oxide materials. The surface electrode layer 11 is formed separately for each of the cells 10-1 to 10-4 by the separation groove 20, but the formation position thereof does not coincide with the boundary of the cell formation region R, and the cell to which it belongs. It is formed across a part of the formation region R and a part of the cell formation region R adjacent (adjacent to the left side in the example of this figure). That is, in the cell formation region R, the surface electrode layer 11 that functions in the cell formation region R and the surface electrode layer 11 that functions in the adjacent cell formation region R are formed with the separation groove 20 interposed therebetween. For example, in the cell formation region R in which the cell 10-2 is formed, the surface electrode layer 11-2 constituting a part of the photoelectric conversion element of the cell 10-2 is formed in the substantially left half region, A surface electrode layer 11-1 constituting a part of the photoelectric conversion element of the cell 10-1 is formed in the right half region.

  The first photoelectric conversion layer 13 includes a semiconductor layer having a pin structure in which a p-type semiconductor layer 131, an i-type semiconductor layer 132, and an n-type semiconductor layer 133 are sequentially stacked. Further, the second photoelectric conversion layer 15 has a pin structure in which a p-type semiconductor layer 151, an i-type semiconductor layer 152, and an n-type semiconductor layer 153 are sequentially stacked. The semiconductor layer has a narrower band gap. Furthermore, the third photoelectric conversion layer 17 has a pin structure in which a p-type semiconductor layer 171, an i-type semiconductor layer 172, and an n-type semiconductor layer 173 are sequentially stacked. The semiconductor layer has a narrower band gap. Below, the laminated body which consists of the 1st photoelectric converting layer 13, the 2nd photoelectric converting layer 15, and the 3rd photoelectric converting layer 17 is called the photoelectric converting laminated body 12. FIG. The photoelectric conversion laminate 12 is formed in the cell formation region R, and is separated from the photoelectric conversion laminate 12 in the adjacent cell formation region R by the separation groove 22.

  Here, the first, second and third photoelectric conversion layers 13, 15, 17 include amorphous silicon, microcrystalline silicon, amorphous silicon germanium, microcrystalline silicon germanium, amorphous silicon carbide, microcrystalline silicon carbide, amorphous germanium. Alternatively, a semiconductor material such as microcrystalline germanium, a material in which oxygen or the like is added to the semiconductor material to adjust a band gap, or a mixture of these semiconductor materials can be used. However, it is necessary to sequentially stack semiconductor materials having a wide band gap from the insulating translucent substrate 2 side. In this example, the case where three photoelectric conversion layers are stacked is described, but the stacked photoelectric conversion layers may be two or more layers. Further, in this example, each of the photoelectric conversion layers 13, 15, and 17 has a structure in which a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer are sequentially stacked from the insulating translucent substrate 2 side. An n-type semiconductor layer, an i-type semiconductor layer, and a p-type semiconductor layer may be stacked in this order from the insulating light-transmitting substrate 2 side.

  The back electrode layer 19 is preferably made of a material having high conductivity and high reflectance, and at least one conductive material selected from Ag, Al, Au, Cu, Pt, Cr, etc., or tin oxide, zinc oxide, ITO, etc. A transparent electroconductive oxide material or a material obtained by adding a metal to these transparent electroconductive oxide materials and a laminate of at least one electroconductive material selected from Ag, Al, Au, Cu, Pt, Cr, and the like It is formed. The back electrode layer 19 collects the photocurrent generated by the photoelectric conversion laminate 12 and reflects light having a long wavelength that is difficult to be absorbed by the third photoelectric conversion layer 17 to the third photoelectric conversion layer 17 side. It also has a function.

  The back electrode layer 19 is formed on the entire surface of one side surface in the arrangement direction of the cells 10-1 to 10-4 of the photoelectric conversion laminate 12 with substantially the same thickness, and the bottom surface of the separation groove 21 between the cell formation regions R. Are connected to the surface electrode layer 11 extending from the adjacent cell 10. On the separation groove 21, the front electrode layer 11 and the back electrode layer 19 are electrically connected in the cell formation region R, and the front electrode layer 11 and the back electrode layer 19 are short-circuited as they are. Is in a state. Therefore, a separation groove 22 is provided at a predetermined position of the cell formation region R in the laminate of the photoelectric conversion laminate 12 and the back electrode layer 19. This eliminates a short circuit between the front electrode layer 11 and the back electrode layer 19 of the own cell in the cell formation region R, and a structure is established in which the adjacent cells are connected in series. As a result, the back electrode layer 19 conformally covers the side surfaces in the cell arrangement direction of the photoelectric conversion laminate 12 other than the separation grooves 22. For example, the back electrode layer 19-2 of the cell 10-2 is the bottom of the separation groove 21 between the surface electrode layer 11-1 of the cell 10-1 adjacent to the right side in the figure and the cells 10-2, 10-1. Connected with.

  Here, the separation grooves 21 of the photoelectric conversion laminate 12 are stepped so that the interval between the side surfaces facing the upper part (back electrode layer 19 side) is wider than the lower part (insulating translucent substrate 2 side). It is formed in the shape of a step or a gentle step. Thus, by forming the separation groove 21 in a stepped shape or a gentle stepped shape, the back electrode layer 19 can satisfactorily cover the side surface of the separation groove 21 to the vicinity of the bottom thereof.

  With the above configuration, for example, the back electrode layer 19-2 of the cell 10-2 is connected to the front electrode layer 11-1 of the adjacent cell 10-1, and the front electrode layer 11-2 of the cell 10-2 is adjacent. By being connected to the back electrode layer 19-3 of the cell 10-3 to be repeated and this is repeated, a thin film solar cell module in which the plurality of cells 10 are connected in series is obtained.

  Here, an outline of the operation in the thin film solar cell 1 having such a structure will be described. When sunlight enters from the back surface of the insulating translucent substrate 2 (the surface on which the cell 10 is not formed), the i-type semiconductor layers 132, 152, 1 to 3 of the first to third photoelectric conversion layers 13, 15, 17 At 172, free carriers are generated. The generated free carriers are transported by a built-in electric field formed by the p-type semiconductor layers 131, 151, 171 and the n-type semiconductor layers 133, 153, 173 of the first to third photoelectric conversion layers 13, 15, 17. Current is generated. The current generated in each cell 10 is adjacent through the connecting portion between the front electrode layer 11 and the back electrode layer 19 in the separation groove 21 as shown by current paths I-1 to I-3 in the figure. It flows into the cell 10 and generates a generated current of the entire thin film solar cell module.

  For example, the current I-3 generated in the cell 10-3 of FIG. 1 passes through the surface electrode layer 11-3 and is formed on the side surface and the upper surface of the photoelectric conversion laminate 12 of the adjacent cell 10-4 on the cell 10-3 side. Flow to the back electrode layer 19-4. Moreover, in the thin film solar cell 1 according to Embodiment 1, the back electrode layer 19 formed on the side surface of the photoelectric conversion laminate 12 has a sufficient film thickness from the top to the bottom of the photoelectric conversion laminate 12. Therefore, the electrical resistance of the back electrode layer 19 on the side surface of the photoelectric conversion laminate 12 is low, and the current generated in the cell 10-3 can flow to the cell 10-4 with low loss. This has a structure in which the side surface of the separation groove 21 between adjacent cells is formed in a stepped shape, and when the back surface electrode layer 19 is formed by a sputtering method or the like, the side surface of the photoelectric conversion laminate 12 is formed as the back surface electrode. This is because the layer 19 can be conformally coated.

  Below, the manufacturing method of the thin film solar cell 1 which has the above-mentioned structure is demonstrated. 2-1 to 2-10 are cross-sectional views schematically showing an example of the method for manufacturing the thin-film solar cell according to Embodiment 1 of the present invention. First, a surface electrode layer 11 made of a transparent conductive oxide material such as zinc oxide, tin oxide, or ITO, or a material obtained by adding a metal to these transparent conductive oxide materials is sputtered on the insulating translucent substrate 2. It forms by film-forming methods, such as a method (FIGS. 2-1). After that, a laser beam 201 is irradiated to a predetermined position on the surface electrode layer 11 by a laser scribing method to form a separation groove 20 to separate the surface electrode layer 11 and pattern the surface electrode layer 11 (FIG. 2). 2). The patterning of the surface electrode layer 11 may be performed using a combination of a photolithography method and an etching method, machining, or the like.

  Next, the first photoelectric conversion layer 13 in which the p-type semiconductor layer 131, the i-type semiconductor layer 132, and the n-type semiconductor layer 133 are sequentially formed on the insulating translucent substrate 2 on which the surface electrode layer 11 is formed is formed by CVD. It is formed by a method such as (Chemical Vapor Deposition) method (FIGS. 2-3). Thereafter, a laser beam 201 is irradiated to a predetermined position of the first photoelectric conversion layer 13 by a laser scribing method to form a separation groove 211 in the first photoelectric conversion layer 13 (FIG. 2-4). The separation groove 211 is formed near the boundary region of the cell formation region R and has a first width W1.

  Next, the second photoelectric conversion layer 15 in which the p-type semiconductor layer 151, the i-type semiconductor layer 152, and the n-type semiconductor layer 153 are sequentially formed on the first photoelectric conversion layer 13 is formed by a method such as a CVD method. Form a film (FIGS. 2-5). Here, the second photoelectric conversion layer 15 is formed so as to fill the separation groove 211 formed between the first photoelectric conversion layers 13, and there is a step near the upper portion of the step portion of the first photoelectric conversion layer 13. Has occurred.

  Thereafter, the laser light 201 is irradiated to a predetermined position of the second photoelectric conversion layer 15 by a laser scribing method to form the separation groove 212 (FIG. 2-6). The separation groove 212 is formed within the range of the formation position of the separation groove 211, and has a second width W2 that is narrower than the first width W1. Therefore, in the state of the cross section after the separation groove 212 is formed, the second photoelectric conversion layer 15 covers the step portion of the first photoelectric conversion layer 13 and protrudes from the end portion of the first photoelectric conversion layer 13. It is in a state. Further, the shape of the cross section of the separation groove 212 has a step shape reflecting the step formed in the first photoelectric conversion layer 13.

  Next, the third photoelectric conversion layer 17 in which the p-type semiconductor layer 171, the i-type semiconductor layer 172, and the n-type semiconductor layer 173 are sequentially formed on the second photoelectric conversion layer 15 is formed by a method such as a CVD method. Film (Figure 2-7). Here, the third photoelectric conversion layer 17 is formed so as to fill the separation groove 212 formed between the second photoelectric conversion layers 15, and near the upper portion of the stepped portion formed in the second photoelectric conversion layer 15. Has a step (unevenness).

  Thereafter, a laser beam 201 is irradiated to a predetermined position of the third photoelectric conversion layer 17 by a laser scribing method to form a separation groove 21 (FIGS. 2-8). The separation groove 21 corresponds to the formation position of the separation grooves 211 and 212 and is formed within the range of the formation position of the separation groove 212, and has a third width W3 that is narrower than the second width W2. It shall be. Therefore, the state of the cross section after the separation groove 21 is formed is that the third photoelectric conversion layer 17 covers the step portion (end portion) of the second photoelectric conversion layer 15 and the end portion of the second photoelectric conversion layer 15. It is in a state overhanging. In addition, the cross-sectional shape of the separation groove 21 has a step shape reflecting the step formed in the second photoelectric conversion layer 15.

  In FIGS. 2-3 to 2-8, the first, second, and third photoelectric conversion layers 13, 15, and 17 include amorphous silicon, microcrystalline silicon, amorphous silicon germanium, and microcrystalline silicon germanium. , Semiconductor materials such as amorphous silicon carbide, microcrystalline silicon carbide, amorphous germanium, and microcrystalline germanium, materials in which the band gap is adjusted by adding oxygen or the like to these semiconductor materials, or a mixture of these semiconductor materials may be used. it can. However, the materials are selected such that semiconductor materials having narrow band gaps are sequentially stacked from the first photoelectric conversion layer 13 toward the third photoelectric conversion layer 17.

  Next, a back electrode layer 19 made of a conductive material having a high reflectance and a high electrical conductivity is formed on the photoelectric conversion laminate 12 separated by the separation groove 21 (FIG. 2-9). As the back electrode layer 19, at least one conductive material selected from Ag, Al, Au, Cu, Pt, Cr, or the like, or a transparent conductive oxide material such as tin oxide, zinc oxide, or ITO, or a transparent conductive material thereof. A laminate of a material obtained by adding a metal to an oxide material and at least one conductive material selected from Ag, Al, Au, Cu, Pt, Cr, and the like can be used. At this time, the cross-sectional shape of the separation groove 21 that separates the photoelectric conversion laminates 12 of each cell 10 is not perpendicular to the substrate surface, but has a stepped shape. The back electrode layer 19 is deposited conformally. Thereby, the front electrode layer 11 and the back electrode layer 19 are electrically connected. However, in this state, the back electrode layer 19 is formed on the entire surface of the insulating translucent substrate 2, and thus is short-circuited with the front electrode layer 11 in each cell 10.

  Finally, laser light 201 is irradiated to predetermined positions of the photoelectric conversion laminate 12 and the back electrode layer 19 from the back side of the insulating translucent substrate 2 by a laser scribing method to form separation grooves 22 (FIG. 2). 10). As a result, the back electrode layer 19 between the adjacent cells 10 is electrically insulated, the state in which the front electrode layer 11 and the back electrode layer 19 of the own cell are short-circuited is also eliminated, and the adjacent cells 10 are connected in series. Is done. Through the above steps, the thin film solar cell 1 as shown in FIG. 1 is completed.

  According to the first embodiment, in a thin film solar cell in which cells 10 in which a plurality of photoelectric conversion layers having different band gaps are stacked are connected in series, the lower the layer is formed from the insulating translucent substrate 2 side to the upper layer. Since the photoelectric conversion layer is formed so as to cover the stepped portion of the photoelectric conversion layer and the separation groove 21 between the photoelectric conversion laminates 12 is formed, the back electrode layer 19 covers the side surface and the bottom surface of the separation groove 21. It can be conformally coated. As a result, in the back electrode layer 19 of the separation groove 21, it is possible to suppress an increase in electrical resistance and to extract the current generated in the power generation region (cell 10) to the maximum, and increase the power generation efficiency compared to the conventional case. It has the effect that the made thin film solar cell 1 can be obtained.

  In the structure of the thin-film solar cell 1 according to the first embodiment, the side surface of the photoelectric conversion laminate 12 that contacts the back electrode layer 19 in the separation groove 21 is limited only to the side surface of the uppermost photoelectric conversion layer. Compared with a thin film solar cell having a conventional structure in which the side surfaces of all the photoelectric conversion layers constituting the photoelectric conversion laminate 12 are in contact with the back electrode layer 19, current loss due to leakage from the cell side surface can be reduced. As a result, the power generation efficiency of the thin film solar cell 1 can be improved as compared with the thin film solar cell having a conventional structure.

  Furthermore, since the back electrode layer 19 is formed after providing the step-like separation groove 21 at the boundary between the adjacent cell formation regions R, the back electrode layer 19 is conformally formed on the side and bottom surfaces of the separation groove 21. The back electrode layer 19 does not need to be formed until the depth of the separation groove 21 is full as in the conventional case, and the back electrode layer 19 can be formed with a minimum amount of material. As a result, both the amount of material and time required for forming the back electrode layer 19 can be reduced as compared with the conventional case, and the production throughput can be improved.

Embodiment 2. FIG.
FIG. 3 is a cross-sectional view schematically showing an example of the structure of the thin-film solar cell according to Embodiment 2 of the present invention. In this thin film solar cell 1A, the first intermediate layer 14 is inserted between the first and second photoelectric conversion layers 13 and 15 in the thin film solar cell 1 of Embodiment 1, and the second and third photoelectric cells The second intermediate layer 16 is inserted between the conversion layers 15 and 17, and the third intermediate layer 18 is inserted between the third photoelectric conversion layer 17 and the back electrode layer 19. Moreover, in this Embodiment 2, the laminated body of the 1st-3rd photoelectric converting layers 13, 15, and 17 and the 1st-3rd intermediate | middle layers 14, 16, and 18 is used as the photoelectric converting laminated body 12A. The other structure has the same structure as that of the first embodiment, and the same components as those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  The first to third intermediate layers 14, 16, and 18 are each made of a transparent conductive material such as zinc oxide and ITO, or a silicon-based material such as silicon oxide or silicon nitride doped with impurities to improve conductivity, or It is composed of a film in which two or more layers of these materials are stacked. The first to third intermediate layers 14, 16, and 18 are configured to convert a part of incident light from the photoelectric conversion layers 13, 15, and 17 on the light incident surface side to the photoelectric conversion layers 13, 15, and 17 side. And the remaining light is transmitted to the rear (back) side. Specifically, out of light incident from each photoelectric conversion layer side, light in a wavelength range that can be absorbed by the photoelectric conversion layer is reflected to the photoelectric conversion layer side, and light in other wavelength ranges is transmitted to the rear side. It is desirable to have a function of In this example, the case where three photoelectric conversion layers and three intermediate layers are alternately stacked is described. However, the stacked photoelectric conversion layers and intermediate layers may be multilayers of two or more layers. The intermediate layer need not be provided corresponding to the photoelectric conversion layer.

  Below, the manufacturing method of 1 A of thin film solar cells which have the above-mentioned structure is demonstrated. FIGS. 4-1 to 4-9 are cross-sectional views schematically showing an example of a method for manufacturing a thin-film solar battery according to Embodiment 2 of the present invention. First, as in the first embodiment, a surface electrode layer 11 made of a transparent conductive oxide material is formed on an insulating translucent substrate 2 by a film forming method such as sputtering, and then a method such as laser scribing is performed. Then, the separation groove 20 is formed and separated at a predetermined position, and the surface electrode layer 11 is patterned (FIG. 4A). Here, a case where the separation groove 20 is formed by irradiating the surface electrode layer 11 with the laser light 201 by a laser scribing method is shown.

  Next, the first photoelectric conversion layer 13 in which the p-type semiconductor layer 131, the i-type semiconductor layer 132, and the n-type semiconductor layer 133 are sequentially formed on the insulating translucent substrate 2 on which the surface electrode layer 11 is formed; A first intermediate layer 14 made of a transparent conductive material such as silicon, zinc oxide, or ITO, or a silicon-based material such as silicon oxide or silicon nitride doped with impurities to improve conductivity, and the like is used for a CVD method or the like. It is formed by a method (FIG. 4-2). Thereafter, the separation groove 211 is formed by irradiating the laser beam 201 by a laser scribing method at a predetermined position of the stacked body of the first photoelectric conversion layer 13 and the first intermediate layer 14 (FIG. 4-3). The separation groove 211 is formed near the boundary region of the cell formation region and has a first width W1.

  Next, the second photoelectric conversion layer 15 in which the p-type semiconductor layer 151, the i-type semiconductor layer 152, and the n-type semiconductor layer 153 are sequentially formed on the first intermediate layer 14, silicon oxide, zinc oxide, ITO, and the like. A second intermediate layer 16 made of a transparent conductive material or a silicon-based material such as silicon oxide or silicon nitride doped with impurities to improve conductivity is formed by a method such as CVD (FIG. 4-4). Here, the second photoelectric conversion layer 15 is formed so as to fill the separation groove 211 formed between the stacked body of the first photoelectric conversion layer 13 and the first intermediate layer 14, and the second photoelectric conversion layer 15 A step is formed near the upper portion of the step portion of the first photoelectric conversion layer 13 on the surface of the intermediate layer 16.

  Thereafter, a laser beam 201 is irradiated to a predetermined position of the stacked body of the second photoelectric conversion layer 15 and the second intermediate layer 16 by a laser scribing method to form a separation groove 212 (FIG. 4-5). The separation groove 212 is formed within the range of the formation position of the separation groove 211, and has a second width W2 that is narrower than the first width W1. Therefore, the state of the cross section after the separation groove 212 is formed is that the second photoelectric conversion layer 15 covers the step portion of the first photoelectric conversion layer 13, and from the end (side surface) of the first photoelectric conversion layer 13. Is overhanging. Further, the shape of the cross section of the separation groove 212 has a stepped shape reflecting the stepped portion of the first photoelectric conversion layer 13.

  Next, a third photoelectric conversion layer 17 in which a p-type semiconductor layer 171, an i-type semiconductor layer 172, and an n-type semiconductor layer 173 are sequentially formed on the second intermediate layer 16, silicon oxide, zinc oxide, ITO, and the like. A third intermediate layer 18 made of a transparent conductive material or a silicon-based material such as silicon oxide or silicon nitride doped with impurities to improve conductivity is formed by a method such as CVD (FIG. 4-6). Here, the third photoelectric conversion layer 17 is formed so as to fill the separation groove 212 formed between the stacked body of the second photoelectric conversion layer 15 and the second intermediate layer 16, and the second photoelectric conversion layer 17 is formed. There is a step near the top of the step formed in the layer 15.

  Thereafter, a laser beam 201 is irradiated to a predetermined position of the laminated body of the third photoelectric conversion layer 17 and the third intermediate layer 18 by a laser scribing method to form the separation groove 21 (FIGS. 4-7). The separation groove 21 corresponds to the formation position of the separation grooves 211 and 212, is formed within the range of the formation position of the separation groove 212, and has a third width W3 that is narrower than the second width W2. And Therefore, the state of the cross section after the separation groove 21 is formed is that the third photoelectric conversion layer 17 covers the step portion (side surface) of the second photoelectric conversion layer 15 and the end portion of the second photoelectric conversion layer 15 ( It is overhanging from the side. The cross-sectional shape of the separation groove 21 has a step shape reflecting the step portions of the first and second photoelectric conversion layers 13, 15, or the surface electrode from the upper surface of the third intermediate layer 18. It has a gentle slope towards layer 11.

  In FIGS. 4-2 to 4-7, the first, second, and third photoelectric conversion layers include amorphous silicon, microcrystalline silicon, amorphous silicon germanium, microcrystalline silicon germanium, and amorphous silicon carbide. Alternatively, a semiconductor material such as microcrystalline silicon carbide, amorphous germanium, or microcrystalline germanium, a material in which a band gap is adjusted by adding oxygen or the like to these semiconductor materials, or a mixture of these semiconductor materials can be used. However, the materials are selected such that semiconductor materials having narrow band gaps are sequentially stacked from the first photoelectric conversion layer 13 toward the third photoelectric conversion layer 17.

  Next, a back electrode layer 19 made of a conductive material having high reflectance and high electrical conductivity is formed on the photoelectric conversion laminate 12A separated by the separation groove 21 (FIGS. 4-8). As the back electrode layer 19, at least one conductive material selected from Ag, Al, Au, Cu, Pt, Cr, or the like, or a transparent conductive oxide material such as tin oxide, zinc oxide, or ITO, or a transparent conductive material thereof. A laminate of a material obtained by adding a metal to the conductive oxide material and at least one conductive material selected from Ag, Al, Au, Cu, Pt, Cr, or the like can be used. At this time, the cross-sectional shape formed in the photoelectric conversion laminate 12 is not perpendicular to the substrate surface, but has a stepped shape or a gentle inclination from the upper surface of the third intermediate layer 18 toward the surface electrode layer 11. Therefore, the back electrode layer 19 is deposited conformally on the side surface of the photoelectric conversion laminate 12 and the bottom surface of the separation groove 21. Thereby, the front electrode layer 11 and the back electrode layer 19 are electrically connected. However, in this state, since the back electrode layer 19 is formed on the entire surface of the insulating translucent substrate 2, it is in a state of being short-circuited with the front electrode layer 11 in each cell.

  Finally, the laser beam 201 is irradiated to a predetermined position on the photoelectric conversion laminate 12A from the back surface side of the insulating translucent substrate 2 by a laser scribing method to form a separation groove 22 (FIG. 4-9). As a result, the back electrode layer 19 between adjacent cells is electrically insulated, the state in which the front electrode layer 11 and the back electrode layer 19 of the own cell are short-circuited is also eliminated, and adjacent cells are connected in series. . Through the above steps, a thin film solar cell 1A as shown in FIG. 3 is completed.

  According to the second embodiment, the conductive transparent intermediate layer is inserted between the photoelectric conversion layers and between the photoelectric conversion layer and the back electrode layer. The light use efficiency is improved, and the power generation efficiency of the thin film solar cell 1A can be further improved.

  In the above embodiment, as the thin film solar cell, the insulating translucent substrate 2 is used as the substrate, the transparent conductive material is used as the front electrode layer 11, and the photoelectric conversion layers 13, 15, and 17 are used as the back electrode layer 19. Although the case where a conductive material that reflects light in the wavelength range that is photoelectrically converted is used is shown, the present invention is not limited to this. For example, a translucent or non-translucent substrate is used as the substrate, a conductive material that reflects light in a wavelength range that is photoelectrically converted by the photoelectric conversion layers 13, 15, and 17 is used as the front electrode layer 11, and the back electrode layer The above-described embodiment can be applied to a thin film solar cell having a structure using a transparent conductive material as 19.

  As mentioned above, the manufacturing method of the thin film solar cell concerning this invention is useful for the thin film solar cell in which a photoelectric converting layer is formed with a thin film.

DESCRIPTION OF SYMBOLS 1,1A thin film solar cell 2 Insulating translucent board | substrate 10,10-1-10-4 cell 11,11-1-11-4 Surface electrode layer 12,12A Photoelectric laminated body 13 1st photoelectric converting layer 14 1st 1 intermediate layer 15 second photoelectric conversion layer 16 second intermediate layer 17 third photoelectric conversion layer 18 third intermediate layer 19, 19-2, 19-3 back electrode layer 20, 21, 22, 211, 212 Separation grooves 131, 151, 171 p-type semiconductor layers 132, 152, 172 i-type semiconductor layers 133, 153, 173 n-type semiconductor layers 201 laser light

In order to achieve the above object, a method of manufacturing a thin-film solar cell according to the present invention includes forming a film made of a conductive material on a substrate, and patterning the cells so as to separate the cells, so A first electrode layer forming step of forming a first photoelectric conversion layer, a first photoelectric conversion layer forming step of forming a first photoelectric conversion layer on the substrate on which the first electrode layer is formed, and the first A first groove forming step of forming a first groove having a first width for separating one photoelectric conversion layer for each cell by a laser scribing method ; and on the substrate on which the first photoelectric conversion layer is formed. a second photoelectric conversion layer forming step of forming a second photoelectric conversion layer, before Symbol the second photoelectric conversion second width narrower than the first width within the first forming position of the groove second groove forming step of forming a second groove for separating the layers by laser scribing , With the second photoelectric conversion layer above, characterized in that it comprises a on the side and bottom of the trench, and a second electrode layer forming step of forming a second electrode layer, a.

Claims (10)

A first electrode layer forming step of forming a film made of a conductive material on a substrate and patterning the cells so as to separate each cell to form a first electrode layer of each cell;
A first photoelectric conversion layer forming step of forming a first photoelectric conversion layer on the substrate on which the first electrode layer is formed;
A first groove forming step of forming a first groove having a first width for separating the first photoelectric conversion layer for each cell;
A second photoelectric conversion layer forming step of forming a second photoelectric conversion layer on the substrate on which the first photoelectric conversion layer is formed;
A second groove forming step of separating the second photoelectric conversion layer by a second groove having a second width narrower than the first width within the formation position of the first groove;
A second electrode layer forming step of forming a second electrode layer on the second photoelectric conversion layer and on a side surface and a bottom surface of the groove;
The manufacturing method of the thin film solar cell characterized by including.   The process from the said 2nd photoelectric converting layer formation process to the said 2nd groove | channel forming process is performed repeatedly, The photoelectric converting laminated body containing the said photoelectric converting layer 3 layers or more is formed. The manufacturing method of the thin film solar cell of description.   3. The thin film according to claim 1, wherein in the second photoelectric conversion layer forming step, the second photoelectric conversion layer is formed using a semiconductor material having a small band gap as the distance from the substrate increases. A method for manufacturing a solar cell.   4. The method according to claim 1, wherein an intermediate layer made of a transparent conductive material is further formed on the first photoelectric conversion layer in the first photoelectric conversion layer forming step. 5. Manufacturing method of thin film solar cell.   5. The method according to claim 1, wherein an intermediate layer made of a transparent conductive material is further formed on the second photoelectric conversion layer in the second photoelectric conversion layer forming step. Manufacturing method of thin film solar cell. The substrate is a translucent insulating substrate,
The first electrode layer is made of a transparent conductive material,
The thin film solar according to any one of claims 1 to 5, wherein the second electrode layer is made of a conductive material that reflects light in a wavelength range that is photoelectrically converted by the photoelectric conversion layer. Battery manufacturing method. A first electrode layer formed of a transparent conductive material on a substrate, a photoelectric conversion laminate including a plurality of photoelectric conversion layers having different band gaps in a direction perpendicular to the substrate surface, and a conductive material that reflects light A second electrode layer including the first electrode layer, and the second electrode layer of the cell is adjacent to the second electrode layer in a groove formed between the photoelectric conversion laminate of the adjacent cell. In the thin film solar cell in which a plurality of the cells are connected in series by being connected to the first electrode layer of the cell,
The cross-sectional structure on the side where the groove of the photoelectric conversion laminate is formed is formed so that the side surface on the adjacent cell side of the lower photoelectric conversion layer is covered with the upper photoelectric conversion layer. Thin film solar cell.   The thin film solar cell according to claim 7, wherein the photoelectric conversion laminate is configured by a semiconductor layer having a band gap that increases from the second electrode layer toward the first electrode layer.   The intermediate layer made of a transparent conductive material is further inserted between the photoelectric conversion layers in the photoelectric conversion laminate and / or between the photoelectric conversion laminate and the second electrode layer. The thin film solar cell according to 7 or 8. The substrate is a translucent insulating substrate,
The thin film solar cell according to claim 7, wherein the first electrode layer is provided on the substrate side.

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