JP2011198784A - Thin film solar cell and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily manufacture a thin film solar cell with high photoelectric conversion efficiency.SOLUTION: The thin film solar cell 100 includes a metal layer 11 arranged in contact with a front surface transparent electrode layer 9 and having a pattern on which a light-transmitting region for transmitting light to a photoelectric conversion layer 8 is formed. The metal layer 11 reduces electrical resistance to a collecting hole 1 in the front surface transparent electrode layer 9, and improves photoelectric conversion efficiency. The photoelectric conversion layer and connection wiring layer are divided to form some unit photoelectric conversion parts 120 and some unit connection wiring parts 140, respectively. The unit photoelectric conversion parts 120 are connected in series to each other through a through-hole and connection hole.

Description

  The present invention relates to a thin film photoelectric conversion element and a method for producing the same. More specifically, the present invention relates to a thin film photoelectric conversion element having a reduced resistance of a transparent electrode layer and a method for manufacturing the same.

  In recent years, thin film solar cells have attracted attention as solar cells with a low environmental load for production. A thin-film solar cell is generally used by forming a plurality of photoelectric conversion elements on one surface of a substrate and connecting the photoelectric conversion elements in series on the substrate. Such a configuration is called an integrated thin film solar cell. An example of such an integrated thin film solar cell is proposed in Patent Document 1 (Japanese Patent Publication No. 5-72113).

  Integrated thin film solar cells are roughly classified into a super straight type pin structure and a substrate type nip structure. In a super straight type solar cell, light for power generation passes through a substrate and then enters a power generation layer, that is, a semiconductor layer. For this reason, in the super straight type solar cell, a transparent or translucent substrate is employed, and the substrate is disposed on the light incident side (hereinafter referred to as “front side”) for the power generation layer to be formed. The semiconductor layer in this case employs a pin structure in which a p layer, an i layer, and an n layer are stacked in this order from the substrate side. On the other hand, in a substrate type solar cell, light for power generation enters the semiconductor layer without passing through the substrate. For this reason, in a substrate type solar cell, it is possible to employ an opaque substrate or a substrate with poor translucency, and the substrate is formed on the side opposite to the light incident side (“ “Back side”). The semiconductor layer in this case employs a nip structure in which an n layer, an i layer, and a p layer are stacked in this order from the substrate side. Patent Document 2 (Japanese Patent No. 4248351) proposes a technique for facilitating a patterning process for realizing a series connection structure of a substrate type nip structure.

  Looking closely at the configuration of each of the proposed integrated thin film solar cells, a photoelectric conversion layer in which a back electrode layer, a semiconductor layer, and a front transparent electrode layer are stacked is formed on a substrate. The layer is divided into units (hereinafter referred to as unit photoelectric conversion units) of the photoelectric conversion element or photoelectric conversion unit. Such unit photoelectric conversion units constitute integrated thin film solar cells connected in series by connecting unit photoelectric conversion units adjacent to each other on the substrate. In this case, the series connection is performed by electrically connecting the front transparent electrode layer of one unit photoelectric conversion unit and the back electrode of the other unit photoelectric conversion unit to each other among two adjacent unit photoelectric conversion units. Is called.

Japanese Patent Publication No. 5-72113 Japanese Patent No. 4248351 (Japanese Patent Laid-Open No. 2005-93903) JP 2003-297158 A JP 2002-57357 A

  When manufacturing an integrated thin film solar cell, it is required to overcome several technical problems. One of the problems is related to the electrical resistance of the front transparent electrode layer.

  Specifically, a transparent conductive material such as ITO (tin-doped indium oxide) is employed as a material for the front transparent electrode layer in the thin film photoelectric conversion element. However, generally, the transparent conductive material has a higher electrical resistance than a metal. Actually, the resistivity of the metal is about 2 to 20 μΩ · cm, whereas the resistivity of the transparent conductive material used for the transparent electrode layer is about 400 μΩ · cm. Even if a solar cell is manufactured using a front transparent electrode layer having a high electric resistance, the curve factor (FF) of the solar cell characteristics is lowered, and the photoelectric conversion efficiency (Eff) is also lowered.

  The simplest solution for reducing the electrical resistance of the front transparent electrode layer is to increase the thickness of the front transparent electrode layer. However, the method of increasing the film thickness of the front transparent electrode layer is difficult to employ in solar cells. This is because the technical requirements for the front transparent electrode layer include optical requirements in addition to electrical requirements. Specifically, in order to increase the photoelectric conversion efficiency of the solar cell, it is necessary to absorb light in a wavelength region (generally 400 nm to 1200 nm) used for power generation into the semiconductor layer without loss. For this reason, the front transparent electrode layer disposed on the front side of the semiconductor layer is required to transmit as much light in the wavelength region as possible. That is, the front transparent electrode layer is required to suppress reflection in a wavelength range of about 500 nm to about 700 nm and to suppress absorption on a longer wavelength side (including the near infrared range) than about 700 nm. On the other hand, when a front transparent electrode layer using a transparent conductive material is disposed, both surfaces of the front transparent electrode layer are generally interfaces or surfaces that do not match the refractive index of the surrounding medium. The thickness of the front transparent electrode layer is carefully determined so as to satisfy the condition of low reflection due to the interference of the thin film of the front transparent electrode layer itself in order to suppress the reflection on the surface of such refractive index mismatch. . Moreover, absorption of the transparent conductive material itself is inevitable. Due to these factors, as long as an actual transparent conductive material is used, the reduction in electrical resistance by the method of increasing the film thickness of the front transparent electrode layer inevitably involves a reduction in the amount of light that can be utilized for solar cells. For this reason, this method cannot be adopted. Note that the wavelength region used for power generation described above is a range in which the spectral sensitivity characteristics of one or more semiconductor layers are sensitive.

  In addition, as a technique for solving the problem of electrical resistance, there is a technique in which a very thin metal layer is formed instead of or added to the front transparent electrode layer so that light can pass through the metal layer. Conceivable. However, this method cannot actually be adopted. For example, even when silver (Ag) having a low resistivity is formed to a film thickness as small as about 10 nm, the transmittance is about 70%. The other 30% of light does not contribute to photoelectric conversion. Then, since the influence by the decrease in the light amount becomes larger than the loss due to the resistance of the front transparent electrode layer is reduced, the power generation amount, that is, the photoelectric conversion efficiency (Eff) with respect to the same irradiation light amount is decreased.

  As a completely different method, a method of forming a metal layer grid electrode on the front side of the front transparent electrode layer is known. As one of the methods, a method of forming a grid electrode or a bus bar electrode by printing a metal colloid solution or the like on the surface of a transparent electrode layer has been proposed (Patent Document 3: Japanese Patent Application Laid-Open No. 2003-297158). However, when the grid electrode or the bus bar electrode is formed by printing, the printing application and drying processes are difficult to be uniform, and unevenness is likely to occur. The unevenness increases output variation. Therefore, this proposed method has a problem that it is difficult to increase mass productivity. Further, when an integrated solar cell is manufactured using such printing, precise alignment for connecting wirings for integrating the unit photoelectric conversion units is also required. In addition, it is difficult in itself to form electrodes so as to have a fine pattern by printing. Furthermore, the metal colloid solution proposed in Patent Document 3 has a problem that the solution is very expensive.

  By the way, in a substrate type thin film solar cell, a thin film solar cell having a so-called SCAF (Series Connection through Arts on Film) structure has been proposed as a configuration for series connection (for example, Patent Document 4: JP-A-2002-2002) 57357). In this configuration, a large number of current collecting holes are provided in order to connect the current from the front transparent electrode layer of a certain unit photoelectric conversion unit to the electrode on the back surface of the adjacent unit photoelectric conversion unit. Even when such an arrangement of current collecting holes is used, the electrical resistance of the front transparent electrode layer described above becomes a problem. As a device to be considered when using such current collecting holes, it is conceivable to arrange the current collecting holes so that the distance from each part of the front transparent electrode layer to the current collecting hole is as constant as possible. For this idea, it is desirable to increase the number of current collecting holes or increase the size of the current collecting holes themselves. This is because using such a configuration has the same effect as reducing the electrical resistance of the transparent conductive material of the front transparent electrode layer by reducing the distance that the charge moves through the front transparent electrode layer. It is. This reduction in electrical resistance improves the fill factor and photoelectric conversion efficiency in the power generation region. However, the area of the power generation region is inevitably reduced with this device. This decrease in area becomes a factor that reduces the photoelectric conversion efficiency of the solar battery cell. For this reason, there is a limit to the performance improvement effect by devising the arrangement, number, and size of the current collecting holes.

  An object of the present invention is to solve at least some of the above problems.

  In order to solve the above-described problems, the inventors of the present application have studied various methods for substantially reducing the electrical resistance of the front transparent electrode layer. As a result, the inventors of the present application have found that forming a metal layer so as to be in contact with the front transparent electrode layer while ensuring a light transmission region is a practical and useful solution. It was. By using a metal layer with a pattern that makes use of these findings, it is possible to substantially reduce the collection distance of the transparent electrode layer, and it is possible to increase the fill factor and photoelectric conversion efficiency in a thin film solar cell. Become. In addition, since the light transmission region is provided, the reduction in the area of the power generation region can be minimized. The present invention was created based on such an idea.

  In one embodiment of the present invention, a thin film solar cell is provided. That is, in an aspect of the present invention, an electrically insulating substrate having a first surface and a second surface, a back electrode layer, a semiconductor layer including a nip junction structure, and a front transparent electrode layer are formed on the substrate. A photoelectric conversion layer disposed on the first surface in this order from the first surface side; and a connection wiring layer disposed on the second surface side of the substrate, the photoelectric conversion layer and the connection wiring Each of the layers is divided so as to form several unit photoelectric conversion units and several unit connection wiring units, and any two unit photoelectric conversion units adjacent to each other on the first surface have one unit photoelectric conversion unit. The front transparent electrode layer of the conversion part is electrically connected to any one unit connection wiring part of the second surface through a current collecting hole penetrating the substrate, and the back electrode layer of the other unit photoelectric conversion part is the substrate. Through the connection hole that penetrates A pattern provided with a light transmission region that is connected in series to each other by being electrically connected to the position connection wiring portion, is disposed in contact with the front transparent electrode layer, and transmits light to the photoelectric conversion layer. A thin film solar cell further comprising a formed metal layer is provided.

  In one embodiment of the present invention, a method for manufacturing a thin film solar cell is provided. That is, in one aspect of the present invention, a step of forming a connection hole penetrating an electrically insulating substrate, a step of forming a back electrode layer on the first surface side of the substrate, and a second of the substrate Forming a connection wiring layer on the surface side, forming a current collecting hole penetrating the substrate, forming a semiconductor layer having a nip junction structure on the back electrode layer, and a front transparent electrode Forming a metal layer in contact with the front transparent electrode layer so as to form a pattern provided with a photoelectric conversion layer forming step including a layer forming step in this order, and a light transmission region for transmitting light to the photoelectric conversion portion A step of partitioning the photoelectric conversion layer so as to form several unit photoelectric conversion portions, and a step of partitioning the connection wiring layer so as to form several unit connection wiring portions. Next to each other in plane In any two unit photoelectric conversion units, the front transparent electrode layer of one unit photoelectric conversion unit is electrically connected to any one unit connection wiring unit on the second surface through the current collecting hole, and the other unit photoelectric conversion unit The back electrode layer of the photoelectric conversion part is electrically connected to the one unit connection wiring part through the connection hole, thereby providing a method for manufacturing a thin film solar cell connected in series with each other.

  According to some aspects of the present invention, the value of the sheet resistance of the front transparent electrode layer can be substantially reduced by disposing the metal layer so as to be in contact with the front transparent electrode layer. At this time, the alignment accuracy for arranging the metal layer can achieve the effect even if the accuracy is such that the range in which the metal layer exists is aligned so as to be included in the range in which the front transparent electrode layer is formed. Is possible.

It is a top view (Drawing 1 (a)) and an enlarged plan view (Drawing 1 (b)) showing composition of a thin film solar cell of an embodiment with the present invention. It is a schematic sectional drawing which shows the structure of the thin film solar cell of embodiment with this invention. It is a process flow figure explaining a process of manufacturing a thin film solar cell in an embodiment with the present invention. It is a block diagram which shows the structure of the metal mask used when manufacturing a thin film solar cell in embodiment with this invention. It is explanatory drawing which shows the outline of the mechanism in which electrical resistance reduces in a front transparent electrode layer in one embodiment of this invention. It is a block diagram which shows the structure of the metal mask used when manufacturing a thin film solar cell in embodiment with this invention.

  Hereinafter, embodiments of the present invention will be described. In the following description, unless otherwise specified, common parts or elements are denoted by common reference numerals throughout the drawings. In the drawings, each element of each embodiment is not necessarily shown in a scale ratio.

<First Embodiment>
FIG. 1 is a plan view (FIG. 1 (a)) and an enlarged plan view (FIG. 1 (b)) showing the configuration of the thin film solar cell of the present embodiment, and FIG. 2 shows the thin film solar cell of the present embodiment. It is a schematic sectional drawing which shows a structure, and FIG. 3 is a process flowchart explaining the process of manufacturing a thin film solar cell in this embodiment.

  In the present embodiment, an integrated thin film solar cell 100 having a SCAF (Series Connection through Arts on Film) structure is manufactured. At the time of use, for example, an additional member (such as a sealing member) is appropriately used to ensure weather resistance. These additional members are omitted from the illustration and illustration in order to clearly explain the present embodiment.

In the thin film solar cell 100 having the SCAF structure, as shown in FIG. 1 (a), light is converted into electricity on one surface (first surface) of the substrate 5 on which the current collecting holes 1 and the connection holes 2 are formed. The photoelectric conversion layer to be converted is electrically separated into each unit and divided so that the separation line 3 forms a column of unit photoelectric conversion units 120 ₁ , 120 ₂ ,... 120 _N. Connection wiring layer disposed on the other side of the substrate (second surface) is also the unit connection wiring portion ₁₄₀ 1 by the separating line _4, 140 2, such that the sequence of the · · · 140 _N separated into respective unit It has been. Hereinafter, the symbols used for the unit photoelectric conversion unit and the unit connection wiring unit are indicated by symbols with abbreviations when collectively referred to, and suffixes are added when referring to these individual components. The first surface and the second surface of the substrate 5 are respectively selected from both surfaces forming the thickness of the substrate 5. Here, of the both surfaces of the substrate, the surface on which the photoelectric conversion layer is disposed or formed is defined as the first surface. Further, in each drawing describing the thin film solar cell 100, in each drawing describing a cross section, a surface facing upward is drawn as a first surface, and in each drawing describing a plane, the paper surface is the first surface. It is drawn.

In the thin film solar cell 100, as shown in FIG. 1B, the separation line 3 and the separation line 4 are repeatedly arranged in one direction, but the separation line 3 and the separation line 4 are The positions of the substrates are shifted so that the positions are different from each other. Thus, the position of the partition that forms the unit photoelectric conversion unit 120 and the position of the partition that forms the unit connection wiring unit 140 are staggered. The unit connection wiring unit 140 can be electrically connected to two unit photoelectric conversion units 120 _i and 120 _{i + 1} adjacent to each other on the first surface of the substrate when the unit connection wiring unit 140 _i, that is, the unit connection wiring unit 140 _i is viewed. This region overlaps with another region via the substrate 5.

2 is a cross-sectional view taken along the line AA ′ (FIG. 2B) and a cross-sectional view taken along the line BB ′ (FIG. 2B) in the enlarged plan view of FIG. The current collecting holes 1 and the connection holes 2 formed as openings in the substrate 5 are formed so as to penetrate the substrate 5, and the unit photoelectric conversion portions of the first surface of the first surface pass through the current collection holes 1 and the connection holes 2. Each is configured to be connected in series. That is, for example, looking at the central portion of the thin-film solar cell 100, the unit connection wiring portion are separated by separation lines 4, 4 140 _i is the unit connection wiring portion 140 _i overlaps one unit photoelectric conversion unit 120 _i of To the front transparent electrode layer 9 through the current collecting hole 1. Furthermore, the unit connection wiring part 140 _i is also connected through the connection hole 2 to the back electrode layer 6 of the other unit photoelectric conversion part 120 _{i + 1} that overlaps with the same unit connection wiring part. By repeating this connection configuration, each of the unit connection wiring parts 140 ₁ , 140 ₂ ,... 140 _{N on} the _second surface is used as a wiring, and unit photoelectric conversion units 120 ₁ , 120 ₂ , 120 ... 120 _N are connected in series in the order of their arrangement.

  In the unit photoelectric conversion unit 120, the photoelectric conversion layer is divided by the separation lines 3 and 3. Here, except for both ends where the connection hole 2 is provided, the back electrode layer 6, the semiconductor layer 8 including the nip junction structure, and the front transparent electrode layer 9 are provided on the first surface of the substrate 5 in this order. Yes. On the other hand, the front transparent electrode layer 9 is not formed at both ends where the connection hole 2 is provided (see the vicinity of the connection hole 2 in FIG. 2A). For this reason, the exposed semiconductor layer 8 and the back electrode layer 6 on the substrate side extend to the connection hole 2 at both ends where the connection hole 2 is provided.

  In the thin film solar cell 100 of this embodiment, the metal layer 11 forms a pattern in which a light transmission region that transmits light to the semiconductor layer 8 is provided on the front transparent electrode layer 9, that is, on the front surface. Is further provided. As shown in FIG. 1B, the pattern of the metal layer 11 includes a line portion extending in a direction orthogonal to the separation line 3 and covered with the metal layer 11 in the thin film solar cell 100, and a line portion of each line portion. And a space portion that is provided between them and is not covered with the metal layer 11. The space where the metal layer 11 is not disposed serves as a light passage region. In order to arrange the metal layer 11 of the thin film solar cell 100 in such a pattern, a vapor deposition method using a mask is used. Details thereof will be described later.

  Next, a process of manufacturing the thin film solar cell 100 having such a structure will be described with reference to FIG. First, an insulating substrate 5 (hereinafter referred to as “substrate 5”) is employed as a substrate for manufacturing the thin-film solar cell 100. Specifically, for example, a polyimide film is used. Other examples of the substrate material that can be employed include other insulating plastic films such as PET, PEN, PES, acrylic, and aramid.

  First, an opening for the connection hole 2 is formed in the substrate 5. For this purpose, an opening is provided at a predetermined position of the substrate 5 by a punching die (punch) (connection hole forming step S102). Next, a degassing process S104 for removing gas released from the polyimide film made of the material of the substrate 5 is performed by heating under reduced pressure. The degassing process S104 may be performed either before or after the connection hole forming step S102, or both.

  Thereafter, the back electrode layer 6 is formed on one surface (first surface) of the substrate 5 (back electrode layer forming step S106), and then the first connection is made on the other surface (second surface) of the substrate 5 surface. The wiring layer 7 is formed (first connection wiring layer forming step S108). The back electrode layer 6 is formed by sputtering, for example, so that silver (Ag) has a thickness of 200 nm. Further, Ag is used as the material of the first connection wiring layer 7 in the same manner as the back electrode layer 6. As materials for the back electrode layer 6 and the first connection wiring layer 7, metals such as an Ag alloy, aluminum (Al), copper (Cu), and titanium (Ti) can be used in addition to these. The back electrode layer 6 may be a film having a multilayer structure of a metal layer and a transparent electrode layer. The film formation method for forming the back electrode layer 6 and the first connection wiring layer 7 is not limited to the sputtering method, and a vacuum deposition method, a spray film formation method, a printing method, a coating method, or a plating method can also be employed. .

  When the back electrode layer formation step S106 and the first connection wiring layer formation step S108 are finished, the back electrode layer 6 formed on the first surface of the substrate 5 and the first connection wiring layer 7 formed on the second surface of the substrate 5 Are directly overlapped in the vicinity of the inner wall of the connection hole 2 and are electrically connected to each other.

  When the first connection wiring layer forming step S108 is completed, the current collecting holes 1 are formed in the substrate 5 using a punching die different from the case of the connection holes 2 (current collecting hole forming step S110). At this time, the current collecting hole 1 is formed so as to penetrate not only the substrate 5 but also the back electrode layer 6 and the first connection wiring layer 7 formed in the substrate 5 at that stage. Further, the semiconductor layer 8 is formed on the first surface side of the substrate 5 (semiconductor layer forming step S112). The semiconductor layer 8 is formed with a silicon (Si) layer having a nip structure in which, for example, an amorphous silicon n-layer, i-layer, and p-layer are disposed from the substrate 5 side. Plasma CVD (Chemical Vapor Deposition) is used. In the present embodiment, the film forming method for forming the semiconductor layer 8 is not particularly limited. As described above, it is a preferable example of the film forming method to use the high frequency capacitively coupled plasma CVD method, and further to use a device having a parallel plate type showerhead electrode as a discharge electrode as a film forming device therefor. Other configurations of the semiconductor layer 8 may be a photoelectric conversion layer using microcrystalline Si as an i layer, or a multi-junction type in which an amorphous Si nip structure and a microcrystalline Si nip structure are stacked. A (tandem type) photoelectric conversion layer may be used. As another example of the constituent material of the n layer and the p layer, the present embodiment can be modified so as to use an alloy such as amorphous SiO. In order to make various technical improvements, it is also possible to add SiO, amorphous Si, or microcrystalline Si layers as the interface layer or tunnel junction layer.

  Further, when the semiconductor layer 8 is formed in the present embodiment, another device for increasing the processing efficiency of the film forming process is also useful. For example, a roll-to-roll method of continuously forming a film while continuously transporting the substrate 5 can be adopted as a preferable process for this embodiment. In addition to this, there is also a method (stepping roll method) that operates so as to repeat the transfer mode and the film formation mode and advances the film formation process so that the substrate is stopped in the film formation mode. It can be employed as a preferred process of the embodiment.

  After the photoelectric conversion layer is formed in the semiconductor layer forming step S112, a transparent conductive material is further deposited on the first surface side of the substrate 5 as the front transparent electrode layer 9 (transparent conductive layer forming step S114). At this time, the transparent conductive material is not deposited by applying a mask to both end portions of the photoelectric conversion layer, that is, the portion where the connection hole 2 is provided. As a result, the semiconductor layer 8 is exposed in this portion (FIG. 2B). Even when the unit photoelectric conversion units 120 connected in series are provided so as to form a plurality of columns (not shown), the transparent conductive material is not deposited between the columns. Thus, the transparent conductive layer 9 is prevented from being formed in the region of the connection hole 2.

Various transparent conductive materials can be used as the transparent conductive material for the front transparent electrode layer 9 of the present embodiment, and the material is not particularly limited. This transparent conductive material is typically any one or combination of transparent conductive materials of metal oxides such as ITO, SnO ₂ , TiO ₂ , ZnO, IZO (In ₂ O ₃ —ZnO, registered trademark). (Laminate or mixture) is selected. Furthermore, RF sputtering, DC sputtering, printing method, coating method, etc. can be employed as the film forming method in the transparent conductive layer forming step S114.

  Next, the second connection wiring layer 10 is formed on the entire second surface side of the substrate 5 (second connection wiring layer forming step S116). As the second connection wiring layer 10, a low resistance conductive layer such as a metal material is formed. When the second connection wiring layer forming step S116 is finished, the front transparent electrode layer 9 formed on the first surface of the substrate 5 and the second connection wiring layer 10 formed on the second surface of the substrate 5 are arranged inside the current collecting holes 1. They overlap directly near the wall and are electrically connected to each other. Since the second connection wiring layer 10 is formed on the second surface of the substrate 5 so as to be in contact with the first connection wiring layer 7 as well, these connection wiring layers on the second surface are connected to each other electrically. It forms an integrated connection wiring layer.

  After the second connection wiring layer formation step S116, the metal layer 11 is formed on the surface of the front transparent electrode layer 9 on the first surface side of the substrate 5 so as to form a predetermined pattern using a mask. (Metal layer forming step S118). As the material of the metal layer 11, a metal material such as silver (Ag) can be adopted. In addition, a film having a multilayer structure using a metal material such as an Ag alloy, Al, Cu, or Ti can also be used. Here, factors to be considered when selecting the material of the metal layer are that vapor deposition is possible, deterioration does not occur during a period of use expected for a solar cell product (module), and the like.

  Here, the description based on FIG. 3 will be left, and the mask used in the metal layer forming step S118 will be described in detail. Various masks can be adopted as the mask used in the present embodiment, but a metal metal mask is preferably used. For example, various stainless steels (SUS), 36% Ni—Fe (Invar steel), 42% Ni—Fe (DF-42), etc. can be used. In addition, as a material of a metal mask, since the above-mentioned Invar steel is a low expansion metal, it is preferable. However, in this embodiment, even if a SUS mask is used, the object can be sufficiently achieved. The reason is that even with a SUS mask, it is possible to form a high-definition opening of about 10 μm or more and it is difficult to cause a problem in local dimensional accuracy. In addition, the fact that the accuracy required for alignment in this embodiment is not high also affects the selection of the mask material. That is, the reason why dimensional accuracy over a long distance such as the entire surface of the substrate is generally required is when the layer or film formed by the mask needs to be accurately aligned over the entire surface of the substrate. In the present embodiment, since it is not necessary to ensure the dimensional accuracy of such a long distance, it is not necessarily necessary to adopt a low expansion metal mask in consideration of the influence of heat when forming various layers.

  The pattern formed as the metal layer 11 can be various patterns. Specifically, a typical example of the predetermined pattern in which the metal layer is formed by the metal mask is a repeated pattern of a narrow line portion extending in a certain direction, that is, a stripe pattern. The extending direction of the line portion may be any of vertical, horizontal, and diagonal directions. In this case, the width of each line portion is preferably 1 mm or less, and more preferably 200 μm or less. Further, the lower limit of the width of the line portion is preferably 10 μm or more because the pattern can be formed by the above-described metal mask. Moreover, the repetition period (pitch) of each line part is larger than the width of a line part, and is 10 mm or less. In the present embodiment, the repeated pitch is not necessarily a constant pitch. However, the line portions arranged at regular intervals with a constant pitch are an example of a typical pattern of the metal layer 11.

  When the metal layer 11 has a stripe pattern, a desirable value for the line portion pitch p (FIG. 2B) is determined by the balance between the pitch of the current collecting holes and the size thereof. The pitch value is set from various viewpoints as long as the purpose is to reduce the electrical resistance by the current flowing through the current collecting hole 1. For example, as shown in FIG. 1, it is assumed that the current collecting holes 1 are formed in a row so as to be arranged at a constant interval in a certain direction. For such a row of current collecting holes 1, it is preferable to use a line in which the repetitive pitch of the line portions following the arrangement of the line portions in the direction of the row is smaller than the pitch of the current collecting holes 1. Note that, unlike FIG. 1, when the current collecting hole row and the line portion row are not parallel, the pitch of the line portion is defined to follow the direction of the current collecting hole row. Even in such a non-parallel case, it is preferable to make the pitch of the line portions smaller than the pitch of the current collecting holes as in the case of the parallel case. When configured to have a pitch relationship as described above, each current collecting hole is associated with a ratio of one or more line portions of the metal layer 11 to reduce the electrical resistance of the front transparent electrode layer 9, The effect that the resistance value at the time of current collection of each current collection hole is equalized with respect to each current collection hole is acquired. To give a more specific example, when the current collecting holes 1 having a diameter of about 1 mm are arranged in a line at a pitch of 5 mm, the arrangement of the line portions of the metal layer 11 is arranged in the line as shown in FIG. Is preferably 5 mm or less. Further, it is more preferable that the predetermined pattern on which the metal layer is formed has a pitch of 1 mm, so that at least one line corresponds to one of the current collecting holes.

  A typical example of the pattern of the metal layer 11 selected in consideration of the above-mentioned various technical requirements is when the current collecting holes are arranged to have a diameter of about 1 mm and a pitch of 5 mm. The metal layer 11 has a stripe pattern in which 50 μm wide lines are repeated at a pitch of 1 mm.

  In addition, as for the relationship between the current collection holes and the arrangement of the line portions of the metal layer 11, as described above, it is preferable that the line portions communicate with the peripheral portions of the current collection holes 1. . This is because the effect of reducing the electrical resistance of the front transparent electrode layer with respect to the current collecting hole 1 is obtained. In addition, a configuration in which the line portion does not communicate with the current collecting hole 1 is also a preferable configuration. This is because the function of the metal layer 11 is expected to improve the photoelectric conversion efficiency by reducing the electrical resistance value of the front transparent electrode layer. Of course, it is preferable that the path leading to the current collecting hole 1 is formed by a metal layer to establish a path having a low electrical resistance, but what the metal layer 11 expects is rather to reduce the sheet resistance of the front transparent electrode layer. This is an effect. Further, as a more positive reason, providing a line portion that does not communicate with the current collecting hole 1 is to set a wide allowable range of misalignment in the alignment of the line portion of the metal layer 11. This is also because the production yield of the thin film solar cell is prevented from being reduced by providing the layer 11.

  One of the technical factors considered when forming the pattern of the metal layer 11 is that the metal layer 11 covers the area of the front transparent electrode layer 9 that contributes to photoelectric conversion as a performance factor. The ratio of the area to be processed, that is, the coverage is mentioned. Further, the effect of reducing the electrical resistance with respect to the front transparent electrode layer 9 is also considered. The reason why the coverage is taken into account is that the amount of light reaching the photoelectric conversion layer is inevitably reduced by the metal layer. Although reducing the coverage rate increases the amount of light, the effect of reducing the electrical resistance by the metal layer 11 is also limited. Conversely, increasing the coverage is advantageous in terms of the effect of reducing the electrical resistance by the metal layer 11, but the amount of light decreases. Considering these, the coverage is preferably 10% or less. Note that the effect of reducing the electrical resistance also depends on the thickness of the metal layer 11. In order to enhance the effect of reducing electrical resistance, it is also preferable to increase the thickness of the metal layer 11. On the other hand, when the metal layer 11 is a very thin film, it is also preferable to reduce the layer thickness of the metal layer 11 in consideration of light transmission.

  In addition to these performance factors, when patterning using a metal mask as in the present embodiment, restrictions caused by the formation method, for example, ease of fabrication of the metal mask, fixing of the metal mask, etc. Ease is also considered.

  Hereinafter, the metal mask used in this embodiment will be described in more detail. FIG. 4 is a configuration diagram showing the configuration of a metal mask used when manufacturing a thin-film solar cell in the present embodiment.

  Specifically, FIG. 4 shows a metal mask 200 for forming the pattern of the metal layer 11 shown in FIG. FIG. 4A is an overall view of the metal mask 200. The metal mask 200 is made from a metal plate 22 made of an appropriate material such as SUS. On the metal plate 22, a pattern with fine openings 26 is formed. FIG. 4B shows an enlarged view of the central portion 24 of the metal mask 200. In the metal mask 200, a slit-shaped opening is formed as the opening 26. By forming such a metal mask on the front transparent electrode layer 9 on the first surface of the substrate 5, a line-shaped metal as shown in FIG. 1B in the metal layer forming step S 118. Layer 11 is formed.

  A vapor deposition method that is a preferable method for forming the metal layer 11 in the present embodiment is flash vapor deposition. In flash deposition, deposition is performed by intermittently supplying a metal layer material. For this reason, for example, when the metal layer 11 is formed of an alloy, there is an advantage that the composition of the metal layer 11 is less likely to shift in composition. It is also useful to perform vapor deposition intermittently using a vapor deposition apparatus having a shutter mechanism. When vapor deposition is completed, the metal layer 11 can be formed with a high-definition pattern.

  Returning to FIG. 3 again, after the metal layer forming step S118, patterning is performed on the first surface side of the substrate 5 by the separation line 3 (first surface patterning process S120). By this patterning, the semiconductor layer 8 has the same shape as the back electrode layer 9. The front transparent electrode layer 9 is not formed in the vicinity of the connection hole 2, but the vicinity of the separation line 3 is separated at the same position as the back electrode. As a result, in the shape surrounded by the separation line 3, except for the vicinity of the connection hole 2 at the end, the back surface electrode layer 6, the semiconductor layer 8 (semiconductor layer), and the front transparent electrode layer 9 are stacked in this order. A conversion unit 120 is formed.

In the thin film solar cell 100 of the present embodiment, the patterned metal layer 11 formed so as to be in contact with the front transparent electrode layer 9 in addition to the front transparent electrode layer 9 is simultaneously separated by the first surface patterning process S120. (FIG. 2B). Therefore, even if the two unit photoelectric conversion units 120 _i and 120 _{i + 1 that} are adjacent to each other on the first surface of the substrate 5 are formed so that the metal layer 11 once connects the two, 5 is electrically separated by a separation line 3 on the first surface side.

  In addition, in order to perform the process of forming the unit photoelectric conversion part 120 more reliably, it is also preferable to perform a preliminary patterning process in addition to the first surface patterning process S120 shown here. This preliminary patterning process is performed, for example, at any stage after the back electrode layer forming step S106 and before the semiconductor layer forming step S112. Also in this preliminary patterning process, the patterning is performed so as to separate the back electrode layer 6 at the position of the separation line 3.

  Finally, laser processing is applied to the position of the separation line 4 also on the second surface side of the substrate 5 (second surface patterning process S122). In the second surface patterning process S122, the second connection wiring layer 10 and the first connection wiring layer 7 are simultaneously separated. Thereby, the unit connection wiring part 140 is formed on the second surface of the substrate 5. In the second surface patterning process S122, power extraction electrodes (not shown) are simultaneously electrically separated, that is, individualized, so that the peripheral edge of the substrate 5 overlaps the separation line on the first surface side. Separation lines are drawn by laser processing (both not shown). Thus, when the separation line of the formed 2nd surface is seen, the periphery which encloses all the thin film solar cell elements collectively, and the adjacent boundary (inside of a periphery conductive part) of two rows of series connection solar cell elements ) Has a separation line. No layer remains in the separation line including the separation line 4.

In this way, the electrical paths in the series-connected columns of the unit photoelectric conversion units thus formed are sequentially traced from the left side of the paper surface of FIG. First, the first unit connection from the first unit photoelectric converter 120 ₁ (front transparent electrode layer 9, semiconductor layer 8, back electrode 6) on the left side of FIG. It is connected to the wiring unit 140 _1. The coupled first from the unit connection wiring portion 140 ₁ to the connection hole 2 through the second unit photoelectric conversion unit 120 _2. Hereinafter, this repetition has led is connected to a unit photoelectric conversion unit 120 _N of the N to the unit connection wiring portion 140 _N of the N. Here, in order to take out the output from the overall unit photoelectric conversion layer 120 which are connected in series, for example, the unit connection wiring portion 140 _N of the N also be used as an electrode for taking out the power, first unit Photoelectric It connected to the wiring portion on the back surface electrode 6 or the back electrode 6 that the conversion unit 120 ₁ is also used as an electrode for taking out electric power.

  In order to further enhance the practicality of the thin film solar cell module, a sealing material, a back sheet, and the like are laminated as an exterior. As the sealing material and the back sheet, various resin materials such as EVA, PE, PET, and ETFE are employed. Here, these materials are not shown.

  The metal layer 11 is disposed on the front surface of the front transparent electrode layer 9. Even in such an arrangement, the influence of a decrease in the amount of power generation due to a decrease in the amount of light incident on the photoelectric conversion layer can be suppressed. The reason is that by making the line width of the line portion of the metal layer 11 extremely narrow, it is possible to expect the effect that light is diffracted and the light penetrates into the shadow portion of such a line portion. . If the line width at which such an effect is obtained is, for example, 200 μm or less, preferably 100 μm or less, a sufficient effect can be expected. In addition, when forming a line part with the metal layer 11, it is necessary to consider the lower limit on manufacture for line | wire width. In particular, in the line portion formed through the opening of the mask, the lower limit value of the line width is determined by the line width capable of forming the mask. The specific value is about 10 μm if the mask manufacturing technique is normal.

  In addition, regarding the layer thickness of the metal layer 11, the effect of reducing the electrical resistance can be achieved even with a very small layer thickness. Specifically, the layer thickness of the metal layer 11 is preferably 10 nm or more and 1 μm or less, and more preferably 100 nm or less. In particular, if the layer thickness is very thin, such as 100 nm or less, transmitted light may be generated in the light incident on the metal layer even if it is a metal layer. Since such transmitted light is incident on the photoelectric conversion layer, the adverse effect due to the fact that the light incident on the photoelectric conversion layer is reduced can be alleviated.

  In addition, the thin film solar cell 100 shown in this embodiment reduces the apparent sheet resistance of the front transparent electrode layer by exerting electric conduction on the metal layer patterned with high definition, and exhibits its effect. is there. For this reason, a high-definition mask is used to make the local pattern of the metal layer a high-definition pattern. It should be noted here that the metal layer 11 is formed by patterning with high definition in this way, and the accuracy required for the alignment performed in the formation is different. That is, the effect of reducing the apparent sheet resistance of the front transparent electrode layer realized in this embodiment is achieved by finely producing each line of the metal layer. In this case, for example, it is not always necessary to arrange such lines in precise alignment with other specific wiring or other elements. For this reason, in order to reduce the apparent sheet resistance of the front transparent electrode layer, the entire region where the metal layer 11 is disposed can be adjusted to the extent of the front transparent electrode layer. Thus, it can be said that it is a great advantage in manufacturing that alignment in the μm unit that is patterned is not required. This is because the manufacturing apparatus or method used for disposing the metal layer 11 can be simplified.

  Then, the reason why the inventors of the present application consider the reason why the metal layer 11 reduces the electrical resistance of the front transparent electrode layer 9, that is, the sheet resistance, will be described below. FIG. 5 is a schematic explanatory view for explaining the principle that the electrical resistance decreases in the front transparent electrode layer in the present embodiment. 5A is an enlarged plan view showing the vicinity of a current collecting hole of a thin film solar cell 500 that does not use the metal layer 11 shown for comparison, and FIG. 2 is an enlarged plan view showing a configuration in the vicinity of an electric hole 1. FIG. The configuration of the thin film solar cell 500 is the same as that of the thin film solar cell 100 except that the metal layer 11 is not provided.

  First, regardless of whether the metal layer 11 is formed or not, the current generated at each position of the front transparent electrode layer 9 is supplied from the current collecting holes 1 to the back side of the substrate 5 as unit connecting wiring portions 140 ( (Not shown in FIG. 5). Therefore, the difference between the thin film solar cell 100 and the thin film solar cell 500 in the current path is the path to the current collecting hole 1. Here, in the thin film solar cell 500 (FIG. 5A), the main current path for collecting current from the position 12 to the current collecting hole 1 is a straight path to the current collecting hole 1. As shown in FIG. 5A, this path can be obtained geometrically based on the Cartesian coordinates (x, y) from the position 12 to the closest position from the peripheral edge of the current collecting hole 1.

  On the other hand, in the thin film solar cell 100, the metal layer 11 is formed and it is a line part. Therefore, if the metal layer 11 exhibits a sufficiently lower resistance value than the front transparent electrode layer 9, it is the Cartesian that mainly determines the resistance from the position 12 to the current collecting hole 1 in the configuration shown in FIG. The coordinate is y. That is, when the metal layer 11 in the line portion is arranged, the electric resistance in the path from each position of the front transparent electrode layer to the current collecting hole 1 is almost determined by the distance to the nearest line portion. For this reason, the substantial electrical resistance that affects the charge flowing through the front transparent electrode layer 9 is reduced as the distance is shortened. Of course, the explanation given here is only a simplified explanation. Electrical conduction through the extended path used to explain the origin of the sheet resistance of the thin film is not taken into account, and moreover, a non-zero resistance occurs in the actual metal layer 11. Therefore, it is possible to explain the effect of the metal layer 11 of this embodiment by a more detailed mechanism. However, the inventors consider that the essence of the mechanism for reducing the electrical resistance of the front transparent electrode layer realized in the present embodiment is simply shown by this description.

  When the pattern of the metal layer 11 is formed using the metal mask, the metal layer 11 is deposited while the metal mask is kept stationary relative to the substrate 5. For this reason, the metal mask is held or fixed by some method. At this time, when holding or fixing, tension is applied to the metal mask depending on the properties of the metal mask plate or the metal mask itself. In order to ensure such fixing, the mask is spot welded to, for example, a suitable holder (not shown).

  In order to confirm whether or not the performance of the solar cell is improved by the thin film solar cell 100 described above, an example sample of the thin film solar cell 100 was produced. Moreover, the result of having compared the Example sample of the thin film solar cell 100 with the comparative example sample produced similarly to the above-mentioned thin film solar cell 500 is demonstrated below.

[Example sample]
As an example sample, a thin-film solar battery cell having the configuration of the thin-film solar battery 100 of Embodiment 1 was produced. The manufactured steps are as described with reference to FIG. Specific conditions were as follows. First, a polyimide film having a thickness of 50 μm was used as the substrate 5. In the connection hole forming step S102, the connection hole 2 is opened using a punch, and degassing processing of the polyimide film on the substrate is performed by degassing processing S104 by heating the substrate temperature to 350 ° C. under a reduced pressure of 10 Pa or less. Went. As the back electrode layer in the back electrode layer forming step S106, silver (Ag) was formed by sputtering so as to have a film thickness of 200 nm. The pressure at this time was 1 Pa.

  As the first connection wiring layer forming step S108, the first connection wiring layer 7 was formed on the second surface of the substrate 5 by sputtering Ar gas at a pressure of 2 Pa. After forming the first connection wiring layer, as the first surface patterning step S110, laser processing was performed so that the back surface electrode 6 on the first surface had a predetermined shape. At this time, the back surface electrode 6 was separated from the back surface electrode along with the separation line 4 on the other peripheral portion so as to be surrounded by the separation line. In the current collecting hole forming step S110, a large number of current collecting holes 1 were formed by punching so as to obtain a 5 mm pitch with a diameter of 1 mm.

  Next, as a semiconductor layer forming step S112, a semiconductor layer 8 was formed by plasma CVD on a single-junction amorphous Si solar cell. The layer thickness of each layer of the semiconductor layer 8 was n layer 20 nm, i layer 300 nm, and p layer 20 nm. At this time, it was published using a capacitively coupled plasma method. Specifically, a parallel plate type shower head electrode was used as the discharge electrode of the plasma CVD apparatus, and the semiconductor layer 8 was formed with a discharge frequency of 27.12 MHz at an electrode distance of 20 mm. Note that the substrate 5 was kept stationary when the semiconductor layer 8 was formed.

Further detailed conditions are as follows. First, an n-type amorphous Si layer was formed using a mixed gas of SiH ₄ gas, H ₂ gas, and PH ₃ gas. At this time, the discharge power was 5 W, and the film formation temperature (set temperature of the substrate) was 300 ° C. Next, an i-type amorphous Si layer was formed using a mixed gas of SiH ₄ gas and H ₂ gas. The discharge power at this time was 20 W, and the film formation temperature was 280 ° C. Further, a p-type amorphous Si layer was formed using a mixed gas of SiH ₄ gas, H ₂ gas, and B ₂ H ₆ gas. The discharge power at this time was 5 W and the film formation temperature was 160 ° C.

  Thereafter, as the transparent conductive layer forming step S114, the front transparent electrode layer 9 was formed on the first surface side of the substrate 5 on the produced nip single junction structure made of amorphous Si. ITO was adopted as the transparent conductive material for the front transparent electrode layer 9. In this embodiment, the formation conditions are set to 0.7 Pa by an RF sputtering method using Ar gas, and the layer thickness is set to 70 nm. At this time, the vicinity of the connection hole 2 was masked so that the front transparent electrode layer 9 was not formed in the connection hole 2.

  Next, as a second connection wiring layer formation step S116, a nickel (Ni) layer to be the second connection wiring layer 10 was formed on the entire second surface. The nickel (Ni) layer was formed by sputtering with Ar gas at a pressure of 2 Pa.

  Furthermore, as the metal layer forming step S118, the metal layer 11 was formed on the front transparent electrode layer 9 (ITO layer). At this time, an Ag layer having a thickness of 10 nm was formed by a vacuum deposition method using a SUS metal mask in which slits of 1 mm pitch with an opening width of 50 μm were formed. A flash vapor deposition method was adopted as the vacuum vapor deposition method. Finally, the first surface patterning process S120 and the second surface patterning process S122 were performed.

[Conventional sample]
A comparative example sample having the same structure as the thin film solar cell 500 was produced in the same manner as the example sample except that the metal layer was not formed on the front transparent electrode layer (ITO layer).

Five solar cells each of the above-described example samples and conventional example samples were produced. The current-voltage characteristics were measured for each cell using a solar simulator, and the photoelectric conversion efficiency (Eff) of the solar cell was determined. The light irradiation condition was 100 mW / cm ² . The results are shown in Table 1.

  Table 1 shows the measured value (unit:%) of the actual photoelectric conversion efficiency measured in each solar cell sample, and the photoelectric conversion efficiency in Examples and Conventional Examples calculated from the measured values of each sample. The average value is shown. Although the measurement values vary in both the example sample and the conventional sample, the average value of the photoelectric conversion efficiency of the example sample to which the present embodiment is actually applied is 0.28% compared to the case of the conventional sample. It was confirmed to improve. Thus, in the solar cell which employ | adopts the structure of the thin film solar cell 100 of this embodiment, in comparison with the thin film solar cell 500, it confirmed that a photoelectric conversion efficiency (Eff) could be improved.

  Here, the photoelectric conversion efficiency (Eff) of the example sample is improved with respect to the comparative sample shown in FIG. 5 because of the presence or absence of the front transparent electrode layer, which is a structural difference. The inventors of the present application have determined. That is, in the example sample, the distance (current collection distance) that the charge moves through the front transparent electrode layer is substantially shorter than that in the comparative example sample. For this reason, it is difficult for the curve factor (FF) of the solar cell characteristics to decrease due to the resistance component of the front transparent electrode layer, and the photoelectric conversion efficiency (Eff) is improved. In addition, the inventors of this application are estimating that the reduction of the light quantity which arises by addition of the metal layer 11 is not a problem, and photoelectric conversion efficiency is improving also if it sees as the whole thin film photovoltaic cell.

<First Embodiment: Modification>
The above first embodiment can be variously modified while maintaining its advantages. For example, the position where the metal layer is formed can be other than the position of the metal layer 11 in contact with the front transparent electrode layer (not shown). Typically, even if a metal layer is disposed between the front transparent electrode layer and the semiconductor layer, that is, on the back side of the front transparent electrode layer, the same effect can be obtained. In this case, the metal layer is also divided by the separation line 3 as in the case where the metal layer is arranged on the front surface side of the front transparent electrode layer as shown in FIG. In the case of adopting such a configuration, the material and forming method of the metal layer are selected so that the photoelectric conversion characteristics of the semiconductor layer 8 are not adversely affected.

  Further, the opening pattern of the metal mask shown in FIG. 4B, that is, the pattern of the metal layer can be changed to another pattern. FIG. 6 shows a configuration of a metal mask having another pattern that can be used in place of the above-described metal mask 200. The mask whose enlarged view of the central portion 24A is shown in FIG. 6A is a mask in which openings 28 extending in a direction perpendicular to the slit-shaped openings 26A are provided in the film or plate between the openings 26A. is there. The use of a pattern having such a line portion extending in at least two directions can also be employed as the present embodiment. For example, in the configuration shown in FIG. 6A, the opening 26A and the opening 28 are not connected. One reason for this is that the pattern that can be formed by the metal mask has a situation in which the plate or film of the metal mask itself cannot form an island-like shielding part. In addition, even if the pattern is such that the metal layers are not necessarily formed to be continuous with each other, the apparent sheet resistance of the front transparent electrode layer is sufficiently reduced to increase the photoelectric conversion efficiency. It is also because the effect to improve is acquired.

  In the mask shown in FIG. 6A, for example, by making the opening width of the opening 26A and the opening width of the opening 28 different, the line width of the line portion formed by the opening 26A is widened. It is also possible to reduce the line width of the formed line portion. Thus, it is also preferable to form a wide main line portion and a narrow sub-line portion by varying the line width of the line portion depending on the direction. By configuring the line portion in this way, it is possible to effectively reduce the electrical resistance while suppressing the influence on the photoelectric conversion efficiency by forming a large number of lines with a small line width.

  Further, the masks shown as an enlarged view of the central portion 24B in FIG. 6B are separated from each other in the direction in which the slit-like opening 26B extends. When the openings 26B thus separated are used, the metal layer is not formed in the region corresponding to the separated portion 30, and the metal layer patterns are separated from each other. Also in this case, the metal mask for forming the opening can be manufactured more easily. Furthermore, even if the metal layers having patterns separated from each other in the extending direction are used, the effect of reducing the apparent sheet resistance of the front transparent electrode layer 9 can be sufficiently obtained. Therefore, such a mask can also be used for the thin film solar cell 100 of this embodiment.

  Further, the mask shown as an enlarged view of the central portion 24C in FIG. 6C is separated in the direction in which both the slit-like opening 26C and the opening 28C extending perpendicular to the opening 26C extend. The configuration using the openings 26C and 28C thus separated combines the characteristics of the mask configuration shown in FIG. 6A and the mask configuration shown in FIG. 6B. A mask can also be used for the thin film solar cell 100 of this embodiment.

  In addition, it is also preferable to form the metal layer 11 by using a plurality of masks in the metal layer forming step S118 shown in FIG. As a single mask, since the shielding part for preventing the adhesion of the metal layer 11 cannot form an island-independent shielding part, for example, it is not possible to form a pattern that is continuous in a vertical or horizontal grid or grid. However, when a plurality of masks are employed, for example, in the case of a metal mask, it is possible to form such a pattern.

  Furthermore, it is also a preferred modification that the line portion of the metal layer is not formed near the connection hole. Such a configuration can be easily realized, for example, by appropriately limiting the range in which the mask opening shown in FIG. 4 is provided. The reason why this modification is preferable is that, if a configuration in which the front transparent electrode layer itself is not formed in the vicinity of the connection hole is adopted, the necessity thereof is low. Further, as another reason, since the connection hole is connected to the back electrode of the photoelectric conversion layer and the connection wiring on the back of the substrate, when a conductive metal layer is arranged there, the other part of the metal layer This is because the possibility of short-circuiting increases when the is connected to the front transparent electrode layer.

  The embodiments of the present invention have been specifically described above. The above-described embodiments and examples are described for explaining the invention, and the scope of the invention of the present application should be determined based on the description of the claims. Moreover, the modification which exists in the scope of the present invention including other combinations of each embodiment is also included in a claim.

  The present invention provides a solar cell with improved fill factor and photoelectric conversion efficiency, thereby greatly contributing to the spread or high performance of any power device or electrical device that includes such a solar cell in part. To do.

DESCRIPTION OF SYMBOLS 100, 500 Thin film solar cell 1 Current collection hole 2 Connection hole 3, 4 Separation line 5 Substrate 6 Back electrode layer 7 1st connection wiring layer 8 Semiconductor layer 9 Front transparent electrode layer 10 2nd connection wiring layer 11 Metal layer 12 Position 120 Unit photoelectric conversion unit 140 Unit connection wiring unit 200 Mask (metal mask)
22 Metal plate 24, 24A, 24B, 24C Center part 26, 26A, 26B, 26C, 28, 28C Opening

Claims (36)

An electrically insulating substrate having a first surface and a second surface;
A photoelectric conversion layer in which a back electrode layer, a semiconductor layer including a nip junction structure, and a front transparent electrode layer are arranged in this order from the first surface side on the first surface of the substrate;
A connection wiring layer disposed on the second surface side of the substrate,
The photoelectric conversion layer and the connection wiring layer are partitioned to form several unit photoelectric conversion units and several unit connection wiring units, respectively.
Any two unit photoelectric conversion units adjacent to each other on the first surface are connected to any one unit connection of the second surface through a current collecting hole through which the front transparent electrode layer of one unit photoelectric conversion unit penetrates the substrate. The back electrode layer of the other unit photoelectric conversion unit is electrically connected to the one unit connection wiring unit through a connection hole penetrating the substrate, thereby being connected in series with each other. And
A thin-film solar cell further comprising a metal layer that is disposed in contact with the front transparent electrode layer and forms a pattern provided with a light transmission region that transmits light to the photoelectric conversion layer. The thin film solar cell according to claim 1, wherein the metal layer has a pattern having several line portions that are repeatedly arranged with a space portion serving as the light transmission region interposed therebetween. The thin film solar cell according to claim 2, wherein a width of the line portion is 10 μm or more and 1 mm or less. The thin film solar cell according to claim 3, wherein a width of the line portion is 200 μm or less. The thin film solar cell according to claim 1, wherein the metal layer has a thickness of 10 nm to 1 μm. The thin film solar cell according to claim 5, wherein the metal layer has a thickness of 100 nm or less. The ratio of the area covered by the metal layer in the range is greater than 0% and 10% or less with respect to the area of the range where photoelectric conversion is performed in the front transparent electrode layer.
The thin film solar cell according to claim 1. The thin film solar cell according to claim 2, wherein the metal layer has a pattern having line portions separated from each other in the extending direction. The thin film solar cell according to claim 2, wherein the metal layer has a pattern having a large number of main line portions extending in a first direction and a large number of sub line portions extending in a direction different from the first direction. . The thin film solar cell according to claim 2, wherein the metal layer has a pattern having a large number of line portions extending in at least two directions. A plurality of the current collecting holes are arranged in at least one direction,
The thin film solar cell according to claim 2, wherein the pitch in the one direction of the several line portions is smaller than the pitch of the array of the current collecting holes. The thin film solar cell according to claim 2, wherein at least one of the line portions of the metal layer communicates with a peripheral portion of the current collecting hole. The thin film solar cell according to claim 2, wherein at least one of the line portions of the metal layer does not communicate with a peripheral portion of the current collecting hole. The thin film solar cell according to claim 2, wherein a line portion of the metal layer is not formed near the connection hole. The thin film solar cell according to claim 2, wherein the line portion of the metal layer is separated by a separation line that divides the photoelectric conversion layer into the unit photoelectric conversion portions. The thin film solar according to any one of claims 1 to 15, wherein the metal layer is formed by an evaporation method using a mask having an opening, and a pattern of the metal layer is formed according to a shape of the opening. battery. The thin film solar cell according to any one of claims 1 to 16, wherein the metal layer is disposed on a front side of the front transparent electrode layer. The thin film solar cell according to any one of claims 1 to 16, wherein the metal layer is disposed on a back surface side of the front transparent electrode layer. Forming a connection hole penetrating the substrate having electrical insulation;
Forming a back electrode layer on the first surface side of the substrate;
Forming a connection wiring layer on the second surface side of the substrate;
Forming a current collecting hole penetrating the substrate;
A step of forming a semiconductor layer having a nip junction structure on the back electrode layer, and a step of forming a front transparent electrode layer in this order, a photoelectric conversion layer forming step;
Forming a metal layer in contact with the front transparent electrode layer so as to form a pattern provided with a light transmission region that transmits light to the photoelectric conversion unit;
Dividing the photoelectric conversion layer to form several unit photoelectric conversion parts;
Dividing the connection wiring layer so as to form several unit connection wiring parts;
Including
In any two unit photoelectric conversion units adjacent to each other on the first surface, the front transparent electrode layer of one unit photoelectric conversion unit is electrically connected to any one unit connection wiring unit on the second surface through the current collecting hole. Thin film solar cell manufacturing method in which the back electrode layer of the other unit photoelectric conversion part is electrically connected to the one unit connection wiring part through the connection hole and thus connected in series to each other. . 20. The step of forming the metal layer forms the metal layer so as to form a pattern having several line portions that are repeatedly arranged with a space portion serving as the light transmission region interposed therebetween. Manufacturing method of a thin film solar cell. The method for manufacturing a thin-film solar cell according to claim 21, wherein a width of the line portion is 10 µm or more and 1 mm or less. The method for producing a thin-film solar cell according to claim 20, wherein the step of forming the metal layer is such that the width of the line portion is 200 μm or less. The method for producing a thin-film solar cell according to claim 19, wherein the step of forming the metal layer forms the metal layer so as to have a thickness of 10 nm or more and 1 µm or less. The method for producing a thin-film solar cell according to claim 23, wherein the step of forming the metal layer forms the metal layer so as to have a film thickness of 100 nm or less. In the step of forming the metal layer, the ratio of the area covered by the metal layer to the area of the front transparent electrode layer in which photoelectric conversion is performed is greater than 0% and 10% or less. The method for manufacturing a thin-film solar cell according to claim 19, wherein the metal layer is formed as follows. The method for manufacturing a thin-film solar cell according to claim 20, wherein the step of forming the metal layer forms the metal layer so as to form a pattern having line portions separated from each other in the extending direction. The step of forming the metal layer is such that the metal layer forms a pattern having a plurality of main line portions extending in a first direction and a plurality of sub line portions extending in a direction different from the first direction. The method for manufacturing a thin-film solar cell according to claim 20, wherein the metal layer is formed. The method for manufacturing a thin-film solar cell according to claim 20, wherein the step of forming the metal layer forms the metal layer so as to form a pattern having a large number of line portions extending in at least two directions. A plurality of the current collecting holes are formed by repeating in at least one direction,
In the step of forming the metal layer, the metal layer is formed so that the pitch in the one direction of the several line portions forms a pattern smaller than the pitch of the array of current collecting holes. The manufacturing method of the thin film solar cell of Claim 20. 21. The thin film solar according to claim 20, wherein the step of forming the metal layer forms the metal layer such that at least one of the line portions of the metal layer communicates with a peripheral portion of the current collecting hole. Battery manufacturing method. 21. The thin film according to claim 20, wherein the step of forming the metal layer forms the metal layer so that at least one of the line portions of the metal layer does not communicate with a peripheral edge of the current collecting hole. A method for manufacturing a solar cell. The method for manufacturing a thin-film solar cell according to claim 20, wherein the step of forming the metal layer forms the metal layer so that a line portion of the metal layer is not formed near the connection hole. The method of manufacturing a thin-film solar cell according to claim 20, wherein the step of dividing the photoelectric conversion layer is a step of dividing the line portion of the metal layer by a separation line that divides the photoelectric conversion layer into the unit photoelectric conversion portion. 34. The step of forming the metal layer, the metal layer is formed by an evaporation method using a mask having an opening, and a pattern of the metal layer is formed according to the shape of the opening. The manufacturing method of the thin film solar cell of any one. The method for manufacturing a thin-film solar cell according to any one of claims 19 to 34, wherein the step of forming the metal layer is performed subsequent to the step of forming the front transparent electrode layer. The method for manufacturing a thin-film solar cell according to any one of claims 19 to 34, wherein a step of forming a front transparent electrode layer is performed subsequent to the step of forming the metal layer.

Images