JP2010171127A - Thin-film solar battery, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film solar battery which is excellent in reliability and output characteristics. <P>SOLUTION: In the thin-film solar battery, a plurality of thin-film solar cells each formed by laminating a first electrode layer made of a transparent conductive material, a photoelectric conversion layer made of a semiconductor thin film and performing photoelectric conversion, and a second electrode layer including a conductive layer reflecting light successively arranged on a light transmissive insulating substrate, and adjacent thin-film solar cells are electrically connected to each other in series. The second electrode layer includes a conductive reflecting film made of a silver film and a surface protecting film made of a titanium nitride film and serving as a protecting film for the conductive reflecting film, the conductive reflecting film and surface protecting film being laminated successively in order on the photoelectric conversion layer, and thin-film solar cells at both ends among the plurality of thin film solar cells connected in series each have a lead-out interconnect for power extraction from the thin-film solar cell arranged on the surface protecting film across a conductive adhesion layer made of a conductive adhesive or conductive particle containing resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thin film solar cell and a method for manufacturing the same.

  Conventionally, a general thin film solar cell is connected in series with a plurality of solar cells in which a transparent electrode layer, a p-type semiconductor thin film, an i-type semiconductor thin film, an n-type semiconductor thin film, and a back electrode layer are sequentially formed on a transparent substrate. And have an integrated structure. In such a thin film solar cell, electricity generated by light incident from the transparent substrate side is taken out from both ends of the solar cells connected in series. At both ends, for example, a solder-coated copper wire called a bus bar wiring is attached by ultrasonic solder, a conductive adhesive or the like.

  As such a thin-film solar cell, for example, there is a technique for processing a mounting portion of a bus bar wiring by laser scribing a semiconductor layer and exposing a transparent electrode to which an ultrasonic solder is easily connected (for example, wiring connection) (for example, , See Patent Document 1).

  In addition, for example, when the back electrode layer is removed by laser scribing, damage caused by laser irradiation to the transparent electrode layer, p-type semiconductor thin film, i-type semiconductor thin film, n-type semiconductor thin film, and back electrode layer is reduced. In consideration of corrosion prevention of the back electrode layer composed of two layers of the reflective film and the surface protective film, a combination of silver reflective film: 150 to 350 nm and titanium surface protective film: 10 to 20 nm, and silver reflection A back electrode layer having a combination of a film: 30 to 80 nm and an aluminum surface protective film: 200 to 350 nm has been proposed (see, for example, Patent Document 2).

Japanese Patent No. 3613851 Japanese Patent No. 4061317

  However, according to the technique of the above-mentioned Patent Document 1, when the semiconductor layer on the transparent electrode layer is subjected to laser scribing in order to form the mounting portion of the bus bar electrode, the transparent electrode layer is also exposed to the laser beam and damaged. There is a problem that the wiring resistance of the portion increases. Even if there is no processing damage on the surface of the transparent electrode layer, if the composition of the material of the back electrode layer and the wiring connection method of the bus bar electrode are not properly selected, the resistance between the back electrode layer and the bus bar wiring of the connecting portion is large. There is a problem of becoming. Furthermore, depending on the configuration of the back electrode layer, the reflective film and the protective film constituting the back electrode layer may be formed by a heat treatment in a manufacturing process after the formation of the back electrode layer, for example, a heat treatment at the time of laminating a back sheet for protecting the back surface. There is a problem that connection resistance increases due to mutual diffusion or alloying.

  Also, when ultrasonic solder is used to connect the bus bar electrodes, deterioration of the crystallinity of the semiconductor thin film due to heating during bonding and erosion (erosion) of the back electrode due to solder occurs, resulting in increased connection resistance. There is a problem that.

  On the other hand, according to the technique of the above-mentioned Patent Document 2, in the back electrode layer that is a combination of the silver reflection film and the titanium surface protective film, titanium is easily oxidized and unstable, and there is a problem in terms of durability. Moreover, in the back electrode layer of the combination of the silver reflecting film and the aluminum surface protective film, there is a problem that silver and aluminum are interdiffused to increase the resistance.

  This invention is made | formed in view of the above, Comprising: It aims at obtaining the thin film solar cell excellent in reliability and an output characteristic.

  In order to solve the above-described problems and achieve the object, a thin film solar cell according to the present invention performs photoelectric conversion on a translucent insulating substrate, which includes a first electrode layer made of a transparent conductive material and a semiconductor thin film. A plurality of thin film solar cells in which a photoelectric conversion layer and a second electrode layer including a conductive layer that reflects light are sequentially stacked are disposed, and the adjacent thin film solar cells are electrically connected to each other. A thin film solar cell connected in series, wherein the second electrode layer includes a conductive reflective film made of a silver film and a titanium nitride film sequentially stacked on the photoelectric conversion layer, and protection of the conductive reflective film A plurality of thin film solar cells connected in series, the thin film solar cells at both ends include a conductive adhesive or conductive particles on the surface protective film. Through a conductive adhesive layer made of resin The lead-out wiring for taking out the power from the thin-film solar cells are arranged, characterized by.

  According to the present invention, as the second electrode layer, a conductive reflective film made of a silver film and a surface protective film made of a titanium nitride film are combined, and conductive bonding is used for connection between the surface of the titanium nitride film and the lead-out wiring. By using a conductive adhesive layer made of an agent or a conductive particle-containing resin, there is an effect that it is possible to realize a highly reliable and low resistance wiring connection that is stable against environmental loads.

FIG. 1-1 is a plan view showing a schematic configuration of a thin-film solar cell module according to an embodiment of the present invention. FIG. 1-2 is a perspective view for schematically explaining the configuration of the thin-film solar cell module according to the embodiment of the present invention. 1-3 is a figure for demonstrating the cross-section of the thin film solar cell module concerning embodiment of this invention, and is principal part sectional drawing in the line segment AA 'direction of FIGS. 1-1. . FIGS. 2-1 is a perspective view for demonstrating the manufacturing process of the thin film solar cell module concerning embodiment of this invention. FIGS. FIGS. 2-2 is a perspective view for demonstrating the manufacturing process of the thin film solar cell module concerning embodiment of this invention. FIGS. FIGS. 2-3 is a perspective view for demonstrating the manufacturing process of the thin film solar cell module concerning embodiment of this invention. FIGS. FIGS. 2-4 is a perspective view for demonstrating the manufacturing process of the thin film solar cell module concerning embodiment of this invention. FIGS. FIGS. 2-5 is a perspective view for demonstrating the manufacturing process of the thin film solar cell module concerning embodiment of this invention. FIGS. FIGS. 2-6 is a perspective view for demonstrating the manufacturing process of the thin film solar cell module concerning embodiment of this invention. FIGS. FIGS. 2-7 is a perspective view for demonstrating the manufacturing process of the thin film solar cell module concerning embodiment of this invention. FIGS. FIG. 3 is a characteristic diagram showing connection resistance in the samples of the example and the comparative example. FIG. 4 is a characteristic diagram showing the relationship between the flow rate ratio (mixing ratio) of nitrogen gas, the resistivity of the formed titanium nitride, and the deposition rate of the titanium nitride film in the formation of the titanium nitride film. .

  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 drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings.

Embodiment FIG. 1-1 is a plan view showing a schematic configuration of a thin film solar cell module (hereinafter referred to as a module) 1 which is a thin film solar cell according to an embodiment of the present invention. FIG. 1-2 is a perspective view for schematically explaining the configuration of the module 1. 1-3 is a figure for demonstrating the cross-sectional structure of the module 1, and is principal part sectional drawing in the line segment AA 'direction of FIGS. 1-1.

  As shown in FIGS. 1-2 and 1-3, the module 1 according to the embodiment is a strip-shaped (rectangular) solar battery cell (hereinafter referred to as a cell) formed on a translucent insulating substrate 2. ) A plurality of C are provided, and the cells C are electrically connected in series. As shown in FIGS. 1-2 and 1-3, the cell C is a transparent electrode layer 3, which is a first electrode layer, a photoelectric conversion layer 4, and a second electrode layer on a translucent insulating substrate 2. The back electrode layer 5 and the back electrode layer 5 are sequentially stacked in this order. In addition, power from the plurality of cells C connected in series via the conductive adhesive layer 6 is provided on the back electrode layer 5 of the cell C located at both ends of the plurality of cells C connected in series. The bus bar wiring 7 is provided for taking out the.

  The transparent electrode layer 3 formed on the translucent insulating substrate 2 has stripe-shaped first layers extending in a direction substantially parallel to the short side direction of the translucent insulating substrate 2 and reaching the translucent insulating substrate 2. One groove D1 is formed. By embedding the photoelectric conversion layer 4 in the portion of the first groove D1, the transparent electrode layer 3 is formed separately for each cell so as to straddle the adjacent cells C.

  The photoelectric conversion layer 4 formed on the transparent electrode layer 3 extends in a direction substantially parallel to the short direction of the translucent insulating substrate 2 at a location different from the first groove D1 and is transparent electrode layer A stripe-shaped second groove (connection groove) D2 reaching 3 is formed. The back electrode layer 5 is connected to the transparent electrode layer 3 by embedding the back electrode layer 5 in the second groove (connection groove) D2. And since this transparent electrode layer 3 straddles the cell C which adjoins, one back surface electrode layer 5 of the two adjacent cells and the other transparent electrode layer 3 are electrically connected.

  Further, the back electrode layer 5 and the photoelectric conversion layer 4 have a striped third groove (separation) reaching the transparent electrode layer 3 at a location different from the first groove D1 and the second groove (connection groove) D2. A groove) D3 is formed, and each cell C is separated. In this way, the transparent electrode layer 3 of the cell C is connected to the back electrode layer 5 of the adjacent cell C, whereby the adjacent cells C are electrically connected in series.

  In the figure, an example in which three cells C are connected in series is described. However, the number of connection stages of the cells C is not limited to three, and the number of stages connected in series is appropriately determined from the system design.

The transparent electrode layer 3 is made of a transparent conductive oxide film such as zinc oxide (ZnO), indium tin oxide (ITO), or tin oxide (SnO ₂ ). The transparent electrode layer 3 is made of aluminum (Al), gallium (Ga), indium (In), boron (B), yttrium (Y), silicon (Si), zirconium (Zr), and titanium (Ti) as dopants. It may be a ZnO film using at least one selected element, an ITO film, a SnO ₂ film, or a transparent conductive film formed by laminating these, and it is a transparent conductive film having optical transparency. I just need it. Further, the transparent electrode layer 3 may have a surface texture structure in which irregularities are formed on the surface. This texture structure has a function of scattering incident sunlight and improving the light use efficiency in the photoelectric conversion layer 4.

  The photoelectric conversion layer 4 has a PN junction or a PIN junction, and is configured by laminating one or more thin film semiconductor layers that generate power by incident light. In the present embodiment, as the photoelectric conversion layer 4, p-type hydrogenated amorphous silicon carbide (a-SiC: H), which is the first conductivity type semiconductor layer, from the transparent electrode layer 3 side, a second conductivity type semiconductor layer is used. A laminated film in which an i-type hydrogenated amorphous silicon (a-Si: H) and an n-type hydrogenated amorphous silicon (a-Si: H) as a third conductivity type semiconductor layer are laminated is formed. Yes.

  The other photoelectric conversion layer 4 includes, for example, a p-type hydrogenated microcrystalline silicon (μc-Si: H) layer that is a first conductivity type semiconductor layer, and an i-type hydrogenation that is a second conductivity type semiconductor layer. From a laminated film in which a microcrystalline silicon (μc-Si: H) layer and an n-type hydrogenated microcrystalline silicon (μc-Si: H) layer as a third conductivity type semiconductor layer are laminated, or from the transparent electrode layer 3 side A p-type hydrogenated amorphous silicon carbide (a-SiC: H) layer as a first conductivity type semiconductor layer, an i-type hydrogenated amorphous silicon (a-Si: H) layer as a second conductivity type semiconductor layer, A stacked film in which an n-type hydrogenated microcrystalline silicon (μc-Si: H) layer, which is a three-conductivity type semiconductor layer, is stacked.

  In addition to this, the photoelectric conversion layer 4 may be a laminated film having a tandem structure of thin film polycrystalline silicon, amorphous silicon, microcrystalline silicon, or the like, or a laminated film of copper, indium, selenium, or a cadmium sulfide based semiconductor. A thin film may be used.

  Further, in the case where the photoelectric conversion layer 4 is configured by stacking a plurality of thin film semiconductor layers, microcrystalline silicon monoxide (μc-SiO), aluminum-added zinc oxide (ZnO: Al), or the like between the PIN junctions. An intermediate layer may be inserted to improve the electrical and optical connections between the PIN junctions.

  The back electrode layer 5 is patterned in a shape and position different from that of the photoelectric conversion layer 4, and as shown in FIG. 1-2, the barrier layer 51 and the metal electrode are formed on the photoelectric conversion layer 4 from the photoelectric conversion layer 4 side. The conductive reflective film 52 made of a silver (Ag) film having reflectivity and the surface protective film 53 made of a titanium nitride (TiN) film and being a protective film for the conductive reflective film 52 are laminated. For example, an aluminum-added zinc oxide (ZnO) film is used as the barrier layer 51. In addition, what is necessary is just to provide the barrier layer 51 as needed.

  For the conductive adhesive layer 6, an ordinary paste-like conductive adhesive or a conductive particle-containing resin such as an anisotropic conductive film (ACF) is used. By using a conductive adhesive or a conductive particle-containing resin as the conductive adhesive layer 6, there is an adverse effect on the crystallinity of the semiconductor thin film due to heating at the time of bonding, as in the case of using solder, There is no increase in connection resistance due to the occurrence of deterioration such as erosion (erosion) or destruction of the cell C. Therefore, an increase in connection resistance due to the conductive adhesive layer 6 can be prevented.

  For the bus bar wiring 7, for example, a copper wire or a solder-coated copper wire can be used. Here, the bus bar wiring 7 is a general term for wiring made of, for example, a conductive plate having an elongated, substantially rectangular cross section.

  Here, an outline of the operation of the module 1 according to the embodiment will be described. When sunlight enters from the back surface of the translucent insulating substrate 2 (the surface on which the cell C is not formed), free carriers are generated in the photoelectric conversion layer 4 and current is generated. The current generated in each cell C flows into the adjacent cell C via the transparent electrode layer 3 and the back electrode layer 5, and generates a generated current for the entire module 1.

  According to the thin film solar cell according to the embodiment configured as described above, in the back electrode layer 5, the conductive reflective film 52 made of a silver (Ag) film is replaced with the surface protective film 53 made of a titanium nitride (TiN) film. Therefore, the oxidation or sulfidation of the silver (Ag) film of the conductive reflective film 52 can be suppressed, and the function deterioration as the back electrode layer 5 due to the corrosion of the silver (Ag) film can be sufficiently suppressed. And a thin film solar cell having excellent durability and stability against environmental loads can be obtained. In addition, since the titanium nitride (TiN) film is a low-resistance surface protective film, the wiring resistance of the connection portion due to the mounting of the bus bar wiring 7 is also caused in the connection between the titanium nitride film (TiN) surface and the bus bar wiring. There is no increase.

  Further, since titanium nitride (TiN) is more stable than titanium (Ti) or the like, the conductive reflective film 52 and the surface protective film 53 are interdiffused in the heat treatment in the manufacturing process after the back electrode layer 5 is formed. Connection resistance does not increase due to, for example, alloying. That is, a low-resistance thin-film solar cell can be obtained by combining the conductive reflective film 52 made of a silver (Ag) film and the surface protective film 53 made of a titanium nitride (TiN) film as the back electrode layer 5.

  Moreover, according to the thin film solar cell concerning embodiment, since the surface protective film 53 of the back surface electrode layer 5 and the bus-bar wiring 7 are connected using the conductive adhesive or the conductive particle-containing resin, it is transparent. There is no increase in the wiring resistance of the connecting portion due to the mounting of the bus bar wiring 7 such as damage to the electrode layer 3.

  In addition, since a conductive adhesive or conductive particle-containing resin is used for connection between the surface protective film 53 of the back electrode layer 5 and the bus bar wiring 7, photoelectric conversion at the time of joining the bus bar wiring 7 as in the case of using solder is used. There is no adverse effect on the crystallinity of the thin film semiconductor layer of the photoelectric conversion layer 4 due to heating at a temperature higher than the heat resistant temperature of the layer 4 or erosion (erosion) of the back electrode layer 5. There is no destruction of the cell C. Thereby, it is possible to minimize the final output reduction of the thin film solar cell and to ensure safety.

  Therefore, according to the thin film solar cell concerning embodiment, the thin film solar cell excellent in reliability and an output characteristic is realizable.

  Next, a method for manufacturing the module 1 according to the embodiment configured as described above will be described. FIGS. 2-1 to 2-7 are perspective views for explaining the manufacturing process of the module 1 according to the embodiment and correspond to FIGS. 1-2.

First, the translucent insulating substrate 2 is prepared. As the translucent insulating substrate 2, for example, a flat glass substrate is used (hereinafter referred to as a glass substrate 2). In the present embodiment, a case where an alkali-free glass substrate is used as the glass substrate 2 will be described. In addition, an inexpensive blue plate glass substrate may be used as the glass substrate 2. In this case, in order to prevent diffusion of alkali components from the substrate, silicon oxide is formed as an undercoat layer by plasma enhanced chemical vapor deposition (PCVD). The film (SiO ₂ ) is preferably formed with a film thickness of about 100 nm.

  Next, the transparent electrode layer 3 to be the first electrode layer is formed on one surface side of the glass substrate 2 (FIG. 2-1). As the transparent electrode layer 3, for example, tin oxide is deposited and formed by a sputtering method with a film thickness of 1 μm to 2 μm, and heat treatment and surface processing are performed as necessary. The method for forming the transparent electrode layer 3 is not limited to the sputtering method, and a physical method such as a vacuum deposition method or an ion plating method, or a chemical method such as a spray method, a dip method, or a CVD method is used. May be.

Thereafter, the surface of the transparent electrode layer 3 is etched and roughened with dilute hydrochloric acid to form small irregularities on the surface of the transparent electrode layer 3. However, when the transparent electrode layer 3 of SnO ₂ , ZnO or the like is formed by the CVD method, irregularities are formed on the surface of the transparent electrode layer 3 in a self-organized manner, so that it is necessary to form the irregularities by etching using diluted hydrochloric acid. Absent.

  Next, a part of the transparent electrode layer 3 is cut and removed in a stripe shape in a direction substantially parallel to the transversal direction of the translucent insulating substrate 2, and the transparent electrode layer 3 is patterned into a strip shape to obtain a plurality of transparent The electrode layer 3 is separated (FIG. 2-2). The patterning of the transparent electrode layer 3 is performed by forming a first stripe D1 extending in a direction substantially parallel to the transversal direction of the translucent insulating substrate 2 and reaching the translucent insulating substrate 2 by a laser scribing method. Do by forming. The removed dust generated at this time is cleaned and removed by high-pressure water cleaning, megasonic cleaning, brush cleaning, or the like.

  In order to obtain a plurality of transparent electrode layers 3 separated from each other within the substrate surface on the glass substrate 2 in this way, a method of etching using a resist mask formed by photolithography or the like, or a metal mask was used. A method such as vapor deposition is also possible.

  Next, the photoelectric conversion layer 4 is formed by the plasma CVD method on the transparent electrode layer 3 including the first groove D1 (FIGS. 2-3). In the present embodiment, as the photoelectric conversion layer 4, for example, a p-type hydrogenated amorphous silicon carbide (a-SiC: H) layer and an i-type hydrogenated amorphous silicon (a-Si: from the transparent electrode layer 3 side). An H) layer and an n-type hydrogenated amorphous silicon (a-Si: H) layer are sequentially stacked to form a p-i-n junction type semiconductor thin film. The thickness of each layer is, for example, 20 nm for the p-type hydrogenated amorphous silicon carbide (a-SiC: H) layer, 300 nm for the i-type hydrogenated amorphous silicon carbide (a-Si: H) layer, and n-type Hydrogenated amorphous silicon (a-Si: H) is 30 nm.

  Next, patterning is performed on the photoelectric conversion layer 4 thus formed by laser scribing in the same manner as the transparent electrode layer 3 (FIGS. 2-4). That is, a part of the photoelectric conversion layer 4 is cut and removed in a stripe shape in a direction substantially parallel to the short direction of the translucent insulating substrate 2, and the photoelectric conversion layer 4 is patterned into a strip shape and separated. Patterning of the photoelectric conversion layer 4 is a stripe that extends in a direction substantially parallel to the lateral direction of the translucent insulating substrate 2 and reaches the transparent electrode layer 3 at a location different from the first groove D1 by a laser scribing method. This is done by forming a second groove (connection groove) D2. At this time, the second groove (connection groove) D2 is formed by fusing only the photoelectric conversion layer 4 (p-i-n junction type semiconductor thin film) so as not to damage the transparent electrode layer 3.

  At this time, it is necessary to pay attention to a short circuit between adjacent p-i-n junction type semiconductor thin films, and after the second groove (connection groove) D2 is formed, it adheres to the second groove (connection groove) D2. The scattered matter is washed away with high-pressure water washing, megasonic washing, or brush washing.

  Next, the back electrode layer 5 is formed on the photoelectric conversion layer 4 (FIGS. 2-5). That is, a 100 nm-thick aluminum-added zinc oxide (ZnO) film as the barrier layer 51 and 200 nm-thick silver (Ag) as the conductive reflective film 52 are formed on the photoelectric conversion layer 4 and in the second groove (connection groove) D2. ) A 20 nm thick titanium nitride (TiN) film as the film and the surface protective film 53 is sequentially formed by a reactive DC sputtering method. Further, as a film formation method, another film formation method such as a CVD method may be used.

  After the formation of the back electrode layer 5, a part of the back electrode layer 5 and the photoelectric conversion layer 4 is cut and removed into stripes in a direction substantially parallel to the transversal direction of the translucent insulating substrate 2 and patterned into strips. Are separated into a plurality of cells C (FIG. 2-6). The patterning is performed by laser scribing and extending in a direction substantially parallel to the transversal insulating substrate 2 in a direction different from the first groove D1 and the second groove (connection groove) D2. This is done by forming a striped third groove (separation groove) D3 reaching the electrode layer 3.

  In addition, since it is difficult to make a back electrode layer 5 with a high reflectance absorb a laser directly, it absorbs a laser beam energy in the photoelectric converting layer 4, and blows off the back electrode layer 5 with the photoelectric converting layer 4 locally. Separated in correspondence with a plurality of cells C. Thereby, a module structure in which a plurality of cells C are electrically connected in series is obtained on the translucent insulating substrate 2. In such a module structure, among the plurality of cells electrically connected in series, the cells C at both ends serve as a positive electrode and a negative electrode, respectively. In the case of the present embodiment in which a p-type semiconductor thin film, an i-type semiconductor thin film, and an n-type semiconductor thin film are formed as the photoelectric conversion layer 4 from the translucent insulating substrate 2 side, the left cell in FIG. C1 is the positive electrode, and the right cell C2 is the negative electrode.

  Next, on the surface protective film 53 of the back electrode layer 5 of the cells C1 and C2 at both ends, a conductive adhesive or conductive particle-containing resin is partially formed as the conductive adhesive layer 6 on the portion where the bus bar wiring 7 is disposed. Apply or paste a sheet. Then, for example, a copper wire or a solder-coated copper wire is disposed on the conductive adhesive layer 6 as the bus bar wiring 7, and a heat and pressure treatment is performed as necessary. Thereby, the surface of the surface protective film 53 of both end cells C1, C2 and the bus bar wiring 7 are connected by the conductive adhesive layer 6 (FIGS. 2-7). The module 1 is obtained through the above processing.

  For example, when a conductive particle-containing resin is used as the conductive adhesive layer 6, since the thermocompression bonding temperature is less than 200 ° C., the heat resistance temperature of the semiconductor thin film as the photoelectric conversion layer 4 that is amorphous or microcrystalline. Heating at a temperature of (200 ° C.) or higher does not cause deterioration of the characteristics of the semiconductor thin film. Further, the conductive adhesive layer 6 can also be used as the conductive adhesive layer 6 by selecting a material that can be cured at a temperature lower than 200 ° C. and can be processed in a short time by adapting the curing time to the process. Can do.

  On the other hand, when ultrasonic solder is used as the conductive adhesive layer 6, since the melting point is 217 ° C. to 218 ° C., solder connection is generally performed with the solder iron tip temperature being about 250 ° C. Do. This temperature is equal to or higher than the heat resistance temperature of the semiconductor thin film as the photoelectric conversion layer 4 and is difficult to apply in the thin film solar cell of this structure.

  Thereafter, a part of the back sheet (not shown) is opened, and one of the output tab wirings (not shown) is connected to the other to the bus bar wiring 7. Next, in order to give the module 1 environmental resistance, an adhesive sheet such as an EVA (ethylene vinyl acetate) film is used as an adhesive, and the back is made of, for example, a multilayer polyethylene terephthalate (PET). The sheet is bonded to the sunlight incident side and vacuum laminated. Then, a terminal box (not shown) is bonded on the back sheet, and the previous output tab is connected to each terminal of the terminal box. The module 1 to which the back sheet is bonded is sealed with a waterproof resin (not shown), for example, a silicone resin, and then covered with an aluminum frame (not shown).

  As described above, according to the method for manufacturing a thin-film solar cell according to the embodiment, in the back electrode layer 5, the conductive reflective film 52 made of a silver (Ag) film is replaced with a surface protective film made of a titanium nitride (TiN) film. 53, the oxidation and sulfidation of the silver (Ag) film of the conductive reflective film 52 can be suppressed, and the function deterioration as the back electrode layer 5 due to the corrosion of the silver (Ag) film can be sufficiently suppressed. Thus, a thin film solar cell that is stable against environmental loads and excellent in durability can be obtained. In addition, since the titanium nitride (TiN) film is a low-resistance surface protective film, the wiring resistance of the connection portion due to the mounting of the bus bar wiring 7 is also caused in the connection between the titanium nitride film (TiN) surface and the bus bar wiring. There is no increase.

  Further, since titanium nitride (TiN) is more stable than titanium (Ti) or the like, the conductive reflective film 52 and the surface protective film 53 are interdiffused in the heat treatment in the manufacturing process after the back electrode layer 5 is formed. Connection resistance does not increase due to, for example, alloying. That is, a low-resistance thin-film solar cell can be obtained by combining the conductive reflective film 52 made of a silver (Ag) film and the surface protective film 53 made of a titanium nitride (TiN) film as the back electrode layer 5.

  Moreover, according to the manufacturing method of the thin film solar cell concerning embodiment, the surface protective film 53 and the bus-bar wiring 7 of the back surface electrode layer 5 are connected using a conductive adhesive or conductive particle containing resin. Therefore, there is no increase in the wiring resistance of the connection portion due to the mounting of the bus bar wiring 7 such as damage to the transparent electrode layer 3.

  In addition, since a conductive adhesive or a conductive particle-containing resin is used for the connection between the surface protective film 53 of the back electrode layer 5 and the bus bar wiring 7, when the bus bar wiring 7 is bonded, the temperature exceeds the heat resistance temperature of the photoelectric conversion layer 4. There is no adverse effect on the crystallinity of the thin film semiconductor layer of the photoelectric conversion layer 4 due to heating, and no deterioration such as erosion (erosion) of the back electrode layer 5, and there is no increase in connection resistance or destruction of the cell C due to these. . Thereby, it is possible to minimize the final output reduction of the thin film solar cell and to ensure safety.

  Therefore, according to the method for manufacturing a thin film solar cell according to the embodiment, a thin film solar cell excellent in reliability and output characteristics can be manufactured.

  Next, in order to investigate the characteristics and reliability of the thin-film solar cell according to the embodiment, the following experiment was performed.

  First, a silver (Ag) thin film was formed to a thickness of 200 nm on a glass substrate, and a titanium nitride (TiN) thin film was successively laminated to a thickness of 20 nm to form one elongated wiring. Next, the elongated wiring was divided at a substantially central portion in the longitudinal direction to form two wiring patterns. End faces facing each other in the longitudinal direction of the two wiring patterns were connected with a solder-coated copper wire using a conductive particle-containing resin as an adhesive. Also, solder-coated copper wires were connected to the other ends of the two wiring patterns in the longitudinal direction using conductive particle-containing resin as an adhesive, and leads were formed so that resistance could be measured.

  Using an EVA film generally used in a polycrystalline solar cell module as an adhesive, a back sheet made of multi-layer PET is adhered to the surface of the glass substrate on which the wiring pattern is formed, and vacuum is applied. Laminated. Then, the end surface was sealed with a silicone resin to prepare three samples, and the samples of Example 1, Example 2, and Example 3 were obtained.

  For comparison, two samples were prepared in the same manner as in the example except that an aluminum (Al) thin film was laminated on a glass substrate with a thickness of 300 nm and divided to form two wiring patterns. Samples of Comparative Example 1 and Comparative Example 2 were used.

  As a comparative reference, a silver (Ag) thin film is formed on a glass substrate with a thickness of 200 nm, and an aluminum (Al) thin film is continuously laminated with a thickness of 100 nm and divided to form two wiring patterns. Except for this, two samples were produced in the same manner as in the example, and the samples of Comparative Example 3 and Comparative Example 4 were obtained.

  As a comparative reference, a silver (Ag) thin film is formed on a glass substrate with a thickness of 200 nm, and a titanium (Ti) thin film is continuously laminated with a thickness of 100 nm and divided to form two wiring patterns. Except for the above, one sample was produced in the same manner as in the example and used as the sample of Comparative Example 5.

  The connection resistance (resistance between both ends in the longitudinal direction of the two wiring patterns) was measured for each of the samples of Examples and Comparative Examples 1 to 5 manufactured as described above under any of the following conditions. The measurement was performed using the two leads described above. The result is shown in FIG. FIG. 3 is a characteristic diagram showing connection resistance in the samples of the example and the comparative example.

Condition 1: “immediately after wiring connection” immediately after two wiring patterns are formed on a glass substrate
Condition 2: “After vacuum lamination” after vacuum lamination of back sheet
Condition 3: “After end face sealing” after end face sealing with silicone resin
Condition 4: “After heat treatment at 150 ° C. for 1 hr” as an environmental load that simulates the situation of the maximum temperature of the manufacturing process treatment after end face sealing
Condition 5: After end face sealing, “after high temperature and high humidity test (85 ° C., 85%, 24 hr) treatment”
Condition 6: In “after end face sealing”, “treatment of 48 heat cycles (−45 ° C. to 105 ° C.)”

  FIG. 3 shows that in the case of the samples of Comparative Example 1 and Comparative Example 2, the connection resistance is 0.2 or less under each condition, and a low resistance is obtained. However, the aluminum (Al) thin film used in the samples of Comparative Example 1 and Comparative Example 2 has a lower reflectance than silver (Ag), and the reflectance is insufficient for use as a back electrode layer. Therefore, it is not generally used for the back electrode layer.

  Moreover, in the case of each sample of Comparative Example 3 to Comparative Example 5, the connection resistance increases in the manufacturing process of vacuum laminating (condition 2) and end face sealing (condition 3), and further an environmental load (condition 4) is applied. It can be seen that the connection resistance further increases.

  On the other hand, in the case of each sample of Examples 1 to 3, the connection resistance does not increase even in the manufacturing process of vacuum lamination (Condition 2) and end face sealing (Condition 3). It can be seen that the resistance is as small as Comparative Example 1 and Comparative Example 2, and the connection resistance hardly changes. From this, it has been experimentally confirmed that titanium nitride is suitable as the surface protective film connected to the bus bar wiring in the thin film solar cell having the configuration in which the conductive reflective film and the surface protective film are laminated as the back electrode layer. It was done.

  In addition, when the back electrode layer of the thin-film solar cell has a laminated structure of silver (Ag) and titanium nitride (TiN), it was confirmed that there is no problem in the photoelectric conversion efficiency and laser scribe processability of the cell C. .

The titanium nitride (TiN) film in the above example was formed by performing reactive sputtering in a mixed gas of argon (Ar) and nitrogen (N ₂ ) using a magnetron DC sputtering apparatus. In the formation of such a titanium nitride (TiN) film, the flow rate ratio (mixing ratio) of nitrogen (N ₂ ) gas (N ₂ / (N ₂ + Ar)) and the resistivity of the formed titanium nitride (TiN) 4 shows the relationship between the deposition rate of the titanium nitride (TiN) film and the flow rate ratio (mixing ratio) of nitrogen (N ₂ ) gas in the deposition of the titanium nitride (TiN) film. 5 is a characteristic diagram showing the relationship between the resistivity of the formed titanium nitride (TiN) and the deposition rate of the titanium nitride (TiN) film, in which the resistance of the formed titanium nitride (TiN) is shown in FIG. The rate is indicated by white circles, and the deposition rate of the titanium nitride (TiN) film is indicated by black circles.

As shown in FIG. 4, the deposition rate of the titanium nitride (TiN) film is stable when the nitrogen (N ₂ ) gas flow ratio (N ₂ / (N ₂ + Ar) is 40% by volume or more, and the formed titanium nitride ( It can be seen that the resistivity of TiN) becomes lower as the nitrogen (N ₂ ) gas flow rate ratio is higher.

Also, titanium nitride (TiN) deposited at a nitrogen (N ₂ ) gas flow ratio of 70% by volume is titanium (Ti) and nitrogen (N ₂ ) by Auger Electron Spectroscopy (AES). As a result, it was confirmed that there was no difference between the two. From these, the nitrogen (N ₂₎ gas flow rate ratio of 40% by volume condition, it can be determined that the substantially stable titanium nitride is formed, nitrogen (N ₂₎ gas flow rate ratio of 40 vol% It can be said that substantially stable titanium nitride can be obtained by forming titanium nitride (TiN) by the reactive DC sputtering method under the above conditions. In Examples 1 to 3, titanium nitride (TiN) was formed at a nitrogen gas flow ratio of 70% by volume.

  As described above, the thin-film solar cell according to the present invention is useful for use in an environment where durability is particularly required.

1 Module 2 Translucent insulating substrate (glass substrate)
3 Transparent Electrode Layer 4 Photoelectric Conversion Layer 5 Back Electrode Layer 6 Conductive Adhesive Layer 7 Busbar Wiring 51 Barrier Layer 52 Conductive Reflective Film 53 Surface Protective Film C Solar Cell (Cell)
C1 Solar cell (cell)
C2 Solar cell (cell)
D1 first groove D2 second groove (connection groove)
D3 Third groove (separation groove)

Claims (4)

A first electrode layer made of a transparent conductive material, a photoelectric conversion layer made of a semiconductor thin film for performing photoelectric conversion, and a second electrode layer including a conductive layer for reflecting light are sequentially stacked on the light-transmitting insulating substrate. A plurality of thin film solar cells are disposed, and adjacent thin film solar cells are electrically connected in series,
The second electrode layer includes a conductive reflective film made of a silver film sequentially laminated on the photoelectric conversion layer, and a surface protective film that is a protective film of the conductive reflective film made of a titanium nitride film,
Among the plurality of thin-film solar cells connected in series, the thin-film solar cells at both ends are on the surface protective film via a conductive adhesive layer made of a conductive adhesive or a conductive particle-containing resin. An extraction wiring for taking out electric power from the thin-film solar cell is disposed,
A thin film solar cell characterized by A first electrode layer, a photoelectric conversion layer made of a semiconductor thin film that performs photoelectric conversion, and a second electrode layer on a translucent insulating substrate so that adjacent thin-film solar cells are electrically connected in series. In this order to form a plurality of the thin-film solar cells,
Out of the plurality of thin-film solar cells connected in series, on the second electrode layer of the thin-film solar cell at both ends, a lead-out wiring for taking out power from the thin-film solar cell is formed as a conductive adhesive layer. A second step of disposing via,
Including
In the first step, the second electrode layer is formed by sequentially laminating a conductive reflective film made of a silver film and a surface protective film made of a titanium nitride film, which is a protective film of the conductive reflective film, on the photoelectric conversion layer. Including the step of forming
In the second step, an extraction wiring for extracting electric power from the thin-film solar cell is disposed on the surface protective film via a conductive adhesive layer made of a conductive adhesive or a conductive particle-containing resin. thing,
A method for producing a thin film solar cell. Forming, as the photoelectric conversion layer, a semiconductor film in which a first conductive semiconductor layer, a second conductive semiconductor layer, and a third conductive semiconductor layer are sequentially stacked from the first electrode layer side;
The manufacturing method of the thin film solar cell of Claim 2 characterized by these. In the first step, a sputtering method is used in which a titanium target is used as a sputtering target, a mixed gas of argon gas and nitrogen gas is used as a sputtering gas, and a mixing ratio of nitrogen gas in the mixed gas is 40% by volume or more. Forming the titanium nitride film;
The manufacturing method of the thin film solar cell of Claim 2 characterized by these.

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