JP2010263015A - Method for forming electrode of solar cell, and method of manufacturing solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming an electrode of a solar cell capable of efficiently, simply and inexpensively forming the electrode. <P>SOLUTION: The method is provided for forming the electrode of the solar cell on an electrode formation surface of a semiconductor substrate. The method includes: a first step of facing a pattern of the electrode in a sheet-like base material with the pattern of the electrode formed on one surface side by an electrode material to the electrode formation surface on the semiconductor substrate, and aligning the pattern with the formation position of the electrode on the electrode formation surface; a second step of bringing one surface side of the sheet-like base material into press contact with the electrode formation surface of the semiconductor substrate by uniformly pressing the entire area of the sheet-like base material including the pattern of the electrode, and transferring the pattern of the electrode to the electrode formation surface of the semiconductor substrate; a third step of separating the sheet-like base material from the electrode formation surface of the semiconductor substrate; and a fourth step of baking the pattern of the electrode transferred to the semiconductor substrate to form the electrode on the electrode formation surface of the semiconductor substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for forming a solar cell electrode and a method for manufacturing a solar cell.

  Conventionally, there is a method using a screen printing method as a typical method for forming a light receiving surface side electrode of a solar cell. In the method using the screen printing method, a printing mask plate (screen plate) having a transmissive portion of a desired pattern is used to print a printing paste on a predetermined position of a silicon substrate, and light is received by high-temperature processing in a baking furnace. A surface side electrode is formed.

  Specifically, first, a stainless steel wire knitted in a net shape called a screen mesh is stretched on the printing plate frame, and tension is fixed by pulling on all sides. Next, a plate film is formed on the screen mesh, and the screen plate is formed by closing the eyes other than the required image line (transmission portion pattern). Then, the produced screen plate is set on a screen printer. Further, a silicon substrate is arranged in alignment with the screen plate.

  Next, the printing paste is placed on the screen plate and spread on the pattern of the transmission part. Subsequently, a rubber-like plate called a squeegee is moved while pressing the plate film inside the screen plate. As a result, the printing paste passes through the screen mesh (transmission pattern) where the plate film is not formed, and is pushed out onto the silicon substrate placed under the screen plate to form a desired pattern. Is done. Thereafter, the printing paste is baked after being dried. Thereby, the light-receiving surface side electrode of a desired pattern is formed. As described above, since the electrode pattern can be easily formed by using the printing plate, this method is most widely used at present.

  On the other hand, a shortage of silicon raw materials is a concern for the rapid spread of silicon solar cells expected in the future. As a countermeasure, by improving the power generation efficiency of solar cells, it is possible to generate large power even with the same amount of raw materials as before, lower the unit price per solar cell power generation amount, and increase the number of production . There is a standard specification for the area of the substrate used for silicon solar cells, and currently 156 mm × 156 mm is generally used, and improving the power generation efficiency per one substrate power generation of the solar cell It leads to improvement of efficiency.

  As one method for improving the power generation efficiency, for example, there is a method of increasing the amount of current obtained from one substrate by ensuring a large area of a substantial light receiving surface that contributes to power generation on the substrate. In this case, it is necessary to form an electrode through which the current generated in the substrate flows, with a minimum area that blocks the light receiving surface.

  When a grid electrode having a thin line width is formed by a conventional screen printing method, the screen mesh is likely to be clogged by the printing paste, and the printing thickness must be reduced to prevent the clogging. As a result, since the cross-sectional area of the grid electrode is reduced and the electrical resistance of the grid electrode itself is increased, a large current obtained from the substrate cannot be connected to an increase in power generation efficiency, and the output characteristics of the solar cell are improved. I can't. Therefore, a plurality of times of overprinting are required to form a thick electrode pattern, and a printing paste capable of being overprinted a plurality of times is required along with improvement of the screen paste printing paste omission. Therefore, this method leads to a complicated printing process, an increase in the number of apparatuses, development of new materials and an increase in price, and a manufacturing cost is greatly increased.

  In addition, in order to form a grid electrode with a certain thickness and a thin line width, the screen printer and its printing conditions, the screen plate and its specifications, and the intricately entangled characteristics such as screen printing print paste are sufficient. It is necessary to build process conditions that are familiar and compatible with these. However, the actual situation is that equipment manufacturers and material manufacturers purchase and manufacture products that are sold in the market for solar cell production, and the grids of the desired shape are not accompanied by the process conditions described above. An electrode cannot be formed. That is, there is a limit to the formation of electrodes by the screen printing method.

  Therefore, as a method for forming the electrodes, a method of transferring the paste applied on the coating roll to the substrate by pressing the coating roll onto the substrate instead of the screen printing method has been considered. Specifically, nozzles for applying a printing paste are arranged in a pattern, the printing paste ejected from the tip of the nozzle is applied in a pattern on a rotating roll, and the roll and the substrate are pressed against each other. Thus, a method of transferring a printing paste onto the substrate is disclosed (for example, see Patent Document 1).

  A typical method for forming the pattern of the light receiving surface electrode by a printing machine equipped with a coating roll is as follows. First, a printing paste is applied in a pattern of a grid electrode on a coating roll from a grid electrode forming nozzle. At the same time, the printing paste is applied in a pattern of bus electrodes on the coating roll from the bus electrode forming nozzle. At this time, the bus electrode forming nozzles are arranged obliquely on the coating roll while synchronizing with the rotation of the bus electrode pattern because the bus electrode pattern is arranged perpendicular to the grid electrode pattern. The printing paste formed in the pattern of the light receiving surface electrode on the coating roll in this way is transferred by pressing the coating roll onto the substrate vacuum-adsorbed on the stage. Thereafter, the pattern transferred to the substrate is dried and then baked.

  In addition, a method is disclosed in which the electrode pattern is not directly transferred from the coating roll to the substrate, but once transferred to a sheet-like base material that disappears after firing, and the sheet-like base material is attached to the substrate (for example, Patent Document 2).

  As another method for forming grid electrodes, a transfer method using a resist used in the manufacture of LSI is imitated. First, a film serving as a resist is pasted on a substrate, and laser processing is applied to the film. A method is disclosed in which after forming an opening having an electrode pattern with a narrower line width than before, a film is removed after embedding a printing paste in the opening, and the film is baked after drying (for example, Patent Document 3). , See Patent Document 4).

JP-A-8-97448 JP 2002-314105 A Japanese Patent Laid-Open No. 5-36998 JP-A-5-326989

  However, in the method according to Patent Document 1, a screen printer and a screen plate are not used, but a printer provided with a coating roll having a complicated mechanism as compared with a screen printer is necessary. For example, the line width is small and the thickness is small. In order to form a thick grid electrode, a conventional printing paste for screen printing is not suitable, so a new suitable printing paste must be developed. Further, the printing process itself is not omitted and it cannot be said that it is a simple process.

  In addition, the method of Patent Document 2 is intended only for the formation of the back surface electrode formed on the entire surface of the substrate, and is not intended for the light receiving surface electrode having a pattern. For the light receiving surface electrode, a conventional method is used. Therefore, it is difficult to form a light receiving surface electrode having a fine pattern such as a grid electrode.

  In addition, it is considered that the methods of Patent Document 3 and Patent Document 4 are easier to form a light-receiving surface electrode having a fine pattern such as a grid electrode than the methods of Patent Document 1 and Patent Document 2, but affixing a film In addition to removal and removal, pattern processing and printing must be performed, which is not an efficient mass production method.

  This invention is made | formed in view of the above, Comprising: It aims at obtaining the electrode formation method of a solar cell and the manufacturing method of a solar cell which can perform electrode formation efficiently and simply and cheaply. .

  In order to solve the above-described problems and achieve the object, an electrode formation method for a solar cell according to the present invention is an electrode formation method for a solar cell in which an electrode is formed on an electrode formation surface of a semiconductor substrate. A first step in which the electrode pattern in the sheet-like base material on which the electrode pattern is formed on one surface is opposed to the electrode formation surface in the semiconductor substrate and aligned with the electrode formation position on the electrode formation surface; Then, the entire surface including the electrode pattern in the sheet-like base material is uniformly pressed to press the one surface side of the sheet-like base material against the electrode forming surface of the semiconductor substrate, and the electrode pattern is A second step of transferring to the electrode forming surface of the semiconductor substrate; a third step of separating the sheet-like base material from the electrode forming surface of the semiconductor substrate; and the semiconductor substrate. A fourth step of forming the electrode on the electrode formation surface of the semiconductor substrate by firing the pattern of the transferred said electrodes, characterized in that it comprises a.

  According to the present invention, in the manufacturing process of the electrode directly on the semiconductor substrate, the electrode printing process itself is not required, and the drying process is not required, so that the solar cell electrode can be manufactured efficiently, simply and inexpensively. There is an effect that can be.

1-1 is sectional drawing which shows schematic structure of the photovoltaic cell concerning Embodiment 1 of this invention. FIG. 1-2 is a top view illustrating a schematic configuration of the solar battery cell according to the first embodiment of the present invention. 1-3 is a bottom view showing a schematic configuration of the solar battery cell according to the first embodiment of the present invention. FIG. FIGS. 2-1 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 2-2 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 2-3 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. FIGS. 2-4 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. FIGS. 2-5 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. FIGS. 2-6 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 2-7 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIG. 3 is a schematic view showing a base film on which a pattern of the light receiving surface side electrode material paste is formed. FIG. 4 is a schematic diagram for explaining the method for forming the electrode of the solar battery cell according to the first embodiment of the present invention. FIG. 5 is a schematic view showing a base film on which a pattern of the light receiving surface side electrode material paste is formed. FIG. 6 is a schematic view showing a state where the pattern of the light receiving surface side electrode material paste is transferred onto the antireflection film together with the second base film.

  EMBODIMENT OF THE INVENTION Below, embodiment of the electrode formation method of the solar cell concerning this invention and the manufacturing method of a solar cell is described in detail based on drawing. 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 1 FIG.
FIGS. 1-1 to 1-3 are diagrams showing a schematic configuration of a solar battery cell 1 manufactured by the method for manufacturing a solar battery according to the present embodiment, and FIG. FIGS. 1 and 2 are top views of the solar battery cell 1 viewed from the light receiving surface side, and FIGS. 1-3 are bottom views of the solar battery cell 1 viewed from the side opposite to the light receiving surface. 1-1 is a cross-sectional view in the AA direction of FIG.

  As shown in FIGS. 1-1 to 1-3, the solar cell 1 is a solar cell substrate having a photoelectric conversion function and having a pn junction, and a light receiving surface side surface of the semiconductor substrate 11. An antireflection film 17 that is formed on the (front surface) and prevents reflection of incident light on the light receiving surface, and a surface (front surface) on the light receiving surface side of the semiconductor substrate 11 is surrounded by the antireflection film 17. A light receiving surface side electrode 19 that is a first electrode formed on the semiconductor substrate 11 and a back surface side electrode 21 that is a second electrode formed on the surface (back surface) opposite to the light receiving surface of the semiconductor substrate 11.

  The semiconductor substrate 11 includes a p-type (first conductivity type) polycrystalline silicon layer 13 and an n-type (second conductivity type) impurity diffusion layer 15 in which the conductivity type of the surface of the p-type polycrystalline silicon layer 13 is inverted. These constitute a pn junction. As the light-receiving surface side electrode 19, the surface silver grid electrode 23 and the surface silver bus electrode 25 of a photovoltaic cell are included. The front silver grid electrode 23 is locally provided on the light receiving surface in order to collect electricity generated by the semiconductor substrate 11. The front silver bus electrode 25 is provided substantially orthogonal to the front silver grid electrode 23 in order to take out the electricity collected by the front silver grid electrode 23. The back electrode 21 is formed on the entire back surface of the semiconductor substrate 11.

  In the solar cell 1 configured as described above, sunlight is irradiated from the light receiving surface side of the solar cell 1 to the pn junction surface of the semiconductor substrate 11 (the junction surface between the p-type polycrystalline silicon layer 13 and the n-type impurity diffusion layer 15). ), Holes and electrons are generated. Due to the electric field at the pn junction, the generated electrons move toward the n-type impurity diffusion layer 15 and the holes move toward the p-type polycrystalline silicon layer 13. As a result, electrons are excessive in the n-type impurity diffusion layer 15 and holes are excessive in the p-type polycrystalline silicon layer 13. As a result, photovoltaic power is generated. This photovoltaic power is generated in the direction of biasing the pn junction in the forward direction, the light receiving surface side electrode 19 connected to the n-type impurity diffusion layer 15 becomes a negative electrode, and the back surface side electrode 21 connected to the p-type polycrystalline silicon layer 13. Becomes a positive pole, and current flows in an external circuit (not shown).

  In the solar cell 1 according to the first embodiment configured as described above, the surface silver grid electrode 23 is a thin wire electrode having a line width of about 80 microns and a thickness of about 25 microns. The area that blocks the surface is reduced as much as possible. Thereby, in the solar cell 1 according to the first embodiment, a substantial area of the light receiving surface that contributes to power generation in the semiconductor substrate 11 is ensured, and the amount of current obtained from the solar cell 1 is increased. The output characteristics are improved.

  Moreover, since the surface silver grid electrode 23 is formed not only with a thin line width but also with a large thickness, a wide cross-sectional area is secured. Thereby, it is prevented that the electrical resistance of the surface silver grid electrode 23 itself increases due to the narrowing of the line width of the surface silver grid electrode 23, and the generated current is connected to the increase in power generation efficiency. The output characteristics are improved.

  Therefore, in the solar cell 1 according to the first embodiment, the light receiving surface side electrode 19 is provided with the thin and thick surface silver grid electrode 23, thereby ensuring a wide light receiving area and excellent photoelectric conversion efficiency. Solar cells have been realized.

  Next, an example of a method for manufacturing such a solar battery cell 1 will be described with reference to FIGS. FIGS. 2-1 to 2-7 are cross-sectional views for explaining a manufacturing process of the solar battery cell 1 according to the first embodiment.

  First, as a semiconductor substrate, for example, a p-type polycrystalline silicon substrate that is most frequently used for consumer solar cells is prepared (hereinafter referred to as a p-type polycrystalline silicon substrate 11a) (FIG. 2-1).

  Since the p-type polycrystalline silicon substrate 11a is manufactured by slicing an ingot formed by cooling and solidifying molten silicon with a wire saw, damage at the time of slicing remains on the surface. Therefore, the p-type polycrystalline silicon substrate 11a is first removed by immersing the surface of the p-type polycrystalline silicon substrate 11a in an acid or heated alkaline solution, for example, in an aqueous solution of sodium hydroxide, to etch the silicon substrate. Then, the damaged region existing near the surface of the p-type polycrystalline silicon substrate 11a is removed.

  At the same time as the damage removal or subsequent to the damage removal, fine unevenness may be formed as a texture structure on the light receiving surface side surface of the p-type polycrystalline silicon substrate 11a (not shown). By providing such a texture structure on the light receiving surface side of the p-type polycrystalline silicon substrate 11a, multiple reflections of light are generated on the surface side of the solar cell 1, and light incident on the solar cell 1 is efficiently transmitted. It can be absorbed inside the semiconductor substrate 11, and the reflectance can be effectively reduced and the conversion efficiency can be improved.

  In addition, since this invention is invention concerning electrode formation, it does not restrict | limit in particular about the formation method and shape of a texture structure. For example, an alkaline aqueous solution containing isopropyl alcohol or a method using acid etching mainly composed of a mixed solution of hydrofluoric acid and nitric acid, or a mask material partially provided with an opening is formed on the surface of the p-type polycrystalline silicon substrate 11a. Any method such as a method of obtaining a honeycomb structure or an inverted pyramid structure on the surface of the p-type polycrystalline silicon substrate 11a by etching through the mask material, or a method using reactive gas etching (RIE) Can be used.

Next, this p-type polycrystalline silicon substrate 11a is put into a thermal oxidation furnace and heated in an atmosphere of phosphorus (P) which is an n-type impurity. Through this step, phosphorus (P) is diffused on the surface of the p-type polycrystalline silicon substrate 11a to form an n-type impurity diffusion layer 15 to form a semiconductor pn junction (FIG. 2-2). In the present embodiment, the n-type impurity diffusion layer 15 is formed by heating the p-type polycrystalline silicon substrate 11a in a phosphorus oxychloride (POCl ₃ ) gas atmosphere at a temperature of, for example, 800 ° C. to 850 ° C.

  Here, since the phosphor glass layer mainly composed of glass is formed on the surface immediately after the formation of the n-type impurity diffusion layer 15, the phosphor glass layer is removed using a hydrofluoric acid solution or the like.

  Next, for example, a silicon nitride film (SiN film) is formed as an antireflection film 17 on the light receiving surface side of the p-type polycrystalline silicon substrate 11a on which the n-type impurity diffusion layer 15 is formed in order to improve the photoelectric conversion efficiency ( Fig. 2-3). For the formation of the antireflection film 17, for example, a plasma CVD method is used, and a silicon nitride film is formed as the antireflection film 17 using a mixed gas of silane and ammonia. The film thickness and refractive index of the antireflection film 17 are set to values that most suppress light reflection. As the antireflection film 17, two or more films having different refractive indexes may be laminated. In addition, a different film forming method such as a sputtering method may be used for forming the antireflection film 17. A silicon oxide film may be formed as the antireflection film 17.

  Next, the n-type impurity diffusion layer 15 formed on the back surface of the p-type polycrystalline silicon substrate 11a is removed by diffusion of phosphorus (P). Thus, the p-type polycrystalline silicon layer 13 as the first conductivity type layer, the n-type impurity diffusion layer 15 as the second conductivity type layer formed on the light receiving surface side of the p-type polysilicon layer 13, Thus, the semiconductor substrate 11 having a pn junction is obtained (FIGS. 2-4).

  The n-type impurity diffusion layer 15 formed on the back surface of the p-type polycrystalline silicon substrate 11a is removed using, for example, a single-sided etching apparatus. Alternatively, a method of using the antireflection film 17 as a mask material and immersing the entire p-type polycrystalline silicon substrate 11a in an etching solution may be used. As the etching solution, an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide heated to room temperature to 95 ° C, preferably 50 ° C to 70 ° C is used. Alternatively, a mixed aqueous solution of nitric acid and hydrofluoric acid may be used as the etching solution.

  Next, the light receiving surface side electrode 19 (before firing), that is, the pattern of the front silver grid electrode 23 and the front silver bus electrode 25 is formed on the antireflection film 17. Here, in the present embodiment, the pattern of the light receiving surface side electrode 19 is formed by transfer as follows.

  First, as shown in FIG. 3, on the base film 31 which is a long sheet-like substrate having a smooth surface in advance, the electrode material of the light-receiving surface side electrode 19 includes silver (Ag), glass, and the like. A pattern of the light receiving surface side electrode material paste 19a is formed in advance. FIG. 3 is a schematic view showing a base film 31 on which a pattern of the light-receiving surface side electrode material paste 19a is formed. The pattern of the light-receiving surface side electrode material paste 19a includes the shape of the light-receiving surface side electrode 19, that is, the shape of the long thin and thick surface silver grid electrode 23 and the strip-shaped surface silver bus electrode substantially orthogonal to the pattern. 25 shapes are formed.

  Further, the pattern of the light receiving surface side electrode material paste 19a is formed by a plurality of units separated by a predetermined distance in the longitudinal direction of the base film 31 with one sheet of the semiconductor substrate 11 as one unit. By forming the pattern of the light receiving surface side electrode material paste 19a on the base film 31 having a smooth surface, which is different from the surface of the semiconductor substrate 11, there is no bleeding in the in-plane direction and the shape in the vertical direction is maintained. An electrode pattern can be formed.

  The method for forming the pattern of the light receiving surface side electrode material paste 19a on the base film 31 is not particularly limited, and for example, a technique such as offset printing or screen printing may be used. As shown in FIG. 4, the base film 31 on which the pattern of the light-receiving surface side electrode material paste 19a is formed is sent out in a roll shape with the pattern of the light-receiving surface side electrode material paste 19a on the outer peripheral side. Set to FIG. 4 is a schematic diagram for explaining the electrode forming method in the present embodiment.

  When the base film 31 is fed from the feed roll 32, it passes through the two sub-rolls 33, passes over the stage 35 that is a holding member of the semiconductor substrate 11, is guided to the take-up roll 34, and is transported. And in the middle of conveyance of this base film 31, position alignment with the base film 31 and the semiconductor substrate 11 is performed, and conveyance of the base film 31 is stopped. That is, the position of the pattern of the light-receiving surface side electrode material paste 19a formed on the base film 31 is matched with the electrode formation position on the semiconductor substrate 11 held on the stage 35 with the light-receiving surface side facing up. Stop the transport.

  Next, the semiconductor substrate 11 and the base film 31 are pressed against each other by pressing and pressing a stamper 36, which is a substantially flat pressing member having an area substantially equal to that of the semiconductor substrate 11, from above the base film 31. Thereafter, the stamper 36 is lifted to separate the base film 31 from the semiconductor substrate 11. Thereby, the pattern of the light-receiving surface side electrode material paste 19a formed on the base film 31 is transferred onto the antireflection film 17 on the surface of the semiconductor substrate 11 (FIG. 2-5). That is, the front silver grid electrode 23 and the front silver bus electrode 25 are formed on the antireflection film 17 as the light receiving surface side electrode 19 (before firing).

  Here, the pressure contact between the semiconductor substrate 11 and the base film 31 may be performed only by pressurization, or may be performed by heating the semiconductor substrate 11 by heating the stage 35 in addition to the pressurization. By heating the semiconductor substrate 11, the adhesion of the light receiving surface side electrode material paste 19 a to the semiconductor substrate 11 can be improved.

  After the transfer of the pattern of the light receiving surface side electrode material paste 19a, the base film 31 is conveyed by a specified length and wound by the winding roll. As a result, the base film 31 at the portion where the pattern of the light-receiving surface side electrode material paste 19a is transferred to the semiconductor substrate 11 is wound on the take-up roll 34, and the pattern of the next light-receiving surface side electrode material paste 19a is placed on the stage 35. Move to. Then, the semiconductor substrate 11 on the stage 35 is replaced, and the above processing is repeated.

  The base film 31 on which the pattern of the light receiving surface side electrode material paste 19a is formed in this way is prepared in advance, and the pattern of the light receiving surface side electrode material paste 19a formed on the base film 31 is transferred to receive light. In the direct manufacturing process of the surface-side electrode 19 on the semiconductor substrate 11, the printing process itself of the light-receiving surface-side electrode material paste is unnecessary, and the drying process of the light-receiving surface-side electrode material paste is also unnecessary. In addition, since the entire light receiving surface of the semiconductor substrate 11 is pressed uniformly, the generation of cracks and chips in the semiconductor substrate 11 is suppressed, and the yield can be improved.

  After the transfer of the light-receiving surface side electrode 19 (before firing), a back-side electrode material paste 21a containing aluminum (Al), glass or the like, which is the electrode material of the back-side electrode 21, is screened on the entire back side of the semiconductor substrate 11. Print and dry at 100-300 ° C (Figure 2-6).

  And the light-receiving surface side electrode 19 and the back surface side electrode 21 are formed by baking the semiconductor substrate 11 at 700 to 1000 degreeC, for example (FIGS. 2-7). Further, the silver in the light receiving surface side electrode 19 penetrates the antireflection film 17, and the n-type impurity diffusion layer 15 and the light receiving surface side electrode 19 are electrically connected.

  By performing the steps as described above, the solar battery cell 1 according to the first embodiment shown in FIGS. 1-1 to 1-3 can be manufactured. In addition, the order of arrangement of the paste, which is an electrode material, on the semiconductor substrate 11 may be switched between the light receiving surface side and the back surface side.

  As described above, in the method for manufacturing the solar cell according to the first embodiment, the light receiving surface formed on the base film 31 without forming the pattern of the light receiving surface side electrode material paste 19a directly on the semiconductor substrate 11. The pattern of the side electrode material paste 19 a is transferred to the semiconductor substrate 11. By adopting such a technique, the process of forming the pattern of the light receiving surface side electrode 19, that is, the thin and thick surface silver grid electrode 23 and the surface silver bus electrode 25, and the formed pattern on the semiconductor substrate 11 are performed. The placing step is separated from the placing step.

  In the former process, the pattern of the light receiving surface side electrode material paste 19a is formed on the base film 31 having a smooth surface, which is different from the semiconductor substrate 11, so that there is no bleeding in the in-plane direction. An electrode pattern having a retained shape can be formed. Moreover, in the latter process, the semiconductor substrate 11 is not pressed while being traced with a screen plate or a roll plate, but the entire light receiving surface of the semiconductor substrate 11 is pressed uniformly. It can suppress and can aim at the improvement of a yield.

  Further, the light receiving surface side electrode 19 can be efficiently formed by transferring the pattern of the light receiving surface side electrode material paste 19a from the base film 31 on which the pattern of the light receiving surface side electrode material paste 19a has been formed in advance. Moreover, the transfer of the pattern of the light-receiving surface side electrode material paste 19a can be performed with a simple apparatus and a simple process, and an electrode can be formed efficiently. And since there is no direct printing process with respect to the semiconductor substrate 11, the apparatus for printing and drying in a manufacturing line becomes unnecessary, and the electrode formation cost can be reduced significantly.

  And in the manufacturing method of the photovoltaic cell concerning Embodiment 1, after passing through processes, such as washing | cleaning, the base film 31 can be recycled, and it can aim at the reduction of cost with resource saving.

  Therefore, in the method for manufacturing the solar cell according to the first embodiment, the thin and thick surface silver grid electrode 23 and the surface silver bus electrode 25 are efficiently, simply and inexpensively manufactured as the light receiving surface side electrode 19. can do. And a photovoltaic cell with a large light receiving area and excellent photoelectric conversion efficiency can be produced efficiently, simply and inexpensively.

Embodiment 2. FIG.
In the second embodiment, a modification of the method for manufacturing a solar battery cell described in the first embodiment will be described. In addition, since the basic process of the manufacturing method of the photovoltaic cell concerning Embodiment 2 is the same as that of the case of Embodiment 1, it demonstrates with reference to FIGS. 2-1-FIGS. 2-4.

  First, the steps described with reference to FIGS. 2-1 to 2-4 in the first embodiment are performed to form a semiconductor substrate 11 having a pn junction as shown in FIG. 2-4. Next, the light receiving surface side electrode 19 (before firing), that is, the pattern of the front silver grid electrode 23 and the front silver bus electrode 25 is formed on the antireflection film 17. Here, in the present embodiment, the pattern of the light receiving surface side electrode 19 is formed by transfer as follows.

  First, as shown in FIG. 5, on a base film 41 which is a long sheet-like base material, a light receiving surface side electrode which is an electrode material of the light receiving surface side electrode 19 and contains silver (Ag), glass or the like. A pattern of material paste 19a is formed. FIG. 5 is a schematic view showing a base film 41 on which a pattern of the light receiving surface side electrode material paste 19a is formed. Here, the base film 41 has a double structure in which a first base film 41a and a second base film 41b having a smooth surface are laminated, and an electrode pattern on the second base film 41b, that is, a light receiving surface side. A pattern of the electrode material paste 19a is formed.

  In addition, the second base film 41b is provided with a cut 42 in the thickness direction so as to partition a region having the same size as the semiconductor substrate 11 containing the pattern of the light receiving surface side electrode material paste 19a. By providing the cut line 42, the second base film 41b can be easily peeled from the first base film 41a in the subsequent transfer process. In addition, a material that disappears in a later baking step is used as the material of the second base film 41b.

  Further, the pattern of the light receiving surface side electrode material paste 19a is formed by a plurality of units separated by a specified distance in the longitudinal direction of the second base film 41b with one sheet of the semiconductor substrate 11 as one unit. By forming the pattern of the light receiving surface side electrode material paste 19a on the second base film 41b having a smooth surface different from the surface of the semiconductor substrate 11, there is no bleeding in the in-plane direction and the shape in the vertical direction is maintained. The formed electrode pattern can be formed.

  The method for forming the pattern of the light receiving surface side electrode material paste 19a on the second base film 41b is not particularly limited, and for example, a technique such as offset printing or screen printing may be used. The base film 41 on which the pattern of the light receiving surface side electrode material paste 19a is formed is wound in a roll shape with the pattern of the light receiving surface side electrode material paste 19a as the outer peripheral side, as in the first embodiment. It is set on the delivery roll 32.

  When the base film 41 is fed from the feed roll 32, it passes through the two sub-rolls 33 and passes over the stage 35 and is guided to the take-up roll 34 to be conveyed. And in the middle of conveyance of this base film 41, position alignment with the base film 41 and the semiconductor substrate 11 is performed, and conveyance of the base film 41 is stopped. That is, the position of the pattern of the light-receiving surface side electrode material paste 19a formed on the base film 41 is matched with the electrode formation position on the semiconductor substrate 11 disposed on the stage 35 with the light-receiving surface side facing up. Stop the transport.

  Next, as in the case of the first embodiment, the stamper 36 is pressed from above the base film 41 and pressed to bring the semiconductor substrate 11 and the base film 41 into pressure contact. Thereafter, the stamper 36 is lifted to separate the base film 41 from the semiconductor substrate 11. As a result, the second base film 41b peels from the first base film 41a along the cut line 42, and the pattern of the light-receiving surface side electrode material paste 19a formed on the second base film 41b is as shown in FIG. The two base films 41b are transferred onto the antireflection film 17 on the surface of the semiconductor substrate 11. That is, the front silver grid electrode 23 and the front silver bus electrode 25 are formed on the antireflection film 17 as the light receiving surface side electrode 19 (before firing) (FIG. 2-5). FIG. 6 is a schematic view showing a state in which the pattern of the light receiving surface side electrode material paste 19a is transferred onto the antireflection film 17 together with the second base film 41b.

  Since the pattern of the light-receiving surface side electrode material paste 19a is peeled off from the first base film 41a together with the second base film 41b and transferred onto the antireflection film 17 on the surface of the semiconductor substrate 11, the first base film 41a and the second base film By adjusting the adhesive strength with the film 41b, the pattern of the light-receiving surface side electrode material paste 19a can be transferred onto the antireflection film 17 with a smaller pressing force than in the case of the first embodiment.

  Further, the pressure contact between the semiconductor substrate 11 and the base film 41 may be performed only by pressurization, or may be performed by heating the semiconductor substrate 11 by heating the stage 35 in addition to the pressurization. By heating the semiconductor substrate 11, the adhesion of the light receiving surface side electrode material paste 19 a to the semiconductor substrate 11 can be improved.

  After the pattern of the light receiving surface side electrode material paste 19a is transferred, the base film 41 is conveyed by a specified length and wound by the winding roll. As a result, the base film 41 where the pattern of the light-receiving surface side electrode material paste 19a is transferred to the semiconductor substrate 11 is taken up by the take-up roll 34, and the pattern of the next light-receiving surface side electrode material paste 19a is placed on the stage 35. Move to. Then, the semiconductor substrate 11 on the stage 35 is replaced, and the above processing is repeated.

  The base film 41 on which the pattern of the light receiving surface side electrode material paste 19a is formed in this way is prepared in advance, and the pattern of the light receiving surface side electrode material paste 19a formed on the base film 41 is transferred. As in the case of the first embodiment, in the direct manufacturing process of the light receiving surface side electrode 19 to the semiconductor substrate 11, the printing process itself of the light receiving surface side electrode material paste is not required, and the drying process of the light receiving surface side electrode material paste is also performed. It becomes unnecessary. In addition, since the entire light receiving surface of the semiconductor substrate 11 is pressed uniformly, the generation of cracks and chips in the semiconductor substrate 11 is suppressed, and the yield can be improved.

  After the transfer of the light-receiving surface side electrode 19 (before firing), a back-side electrode material paste 21a containing aluminum (Al), glass or the like, which is the electrode material of the back-side electrode 21, is screened on the entire back side of the semiconductor substrate 11. Print and dry at 100-300 ° C (Figure 2-6).

  And the light-receiving surface side electrode 19 and the back surface side electrode 21 are formed by baking the semiconductor substrate 11 at 700 to 1000 degreeC, for example (FIGS. 2-7). Further, the silver in the light receiving surface side electrode 19 penetrates the antireflection film 17, and the n-type impurity diffusion layer 15 and the light receiving surface side electrode 19 are electrically connected. Also, the second base film 41b transferred onto the antireflection film 17 together with the pattern of the light receiving surface side electrode material paste 19a is burned off during the firing and disappears.

  By performing the steps as described above, the solar battery cell 1 shown in FIGS. 1-1 to 1-3 can be manufactured. In addition, the order of arrangement of the paste, which is an electrode material, on the semiconductor substrate 11 may be switched between the light receiving surface side and the back surface side.

  As described above, also in the method for manufacturing the solar cell according to the second embodiment, the light receiving surface formed on the base film 41 without directly forming the pattern of the light receiving surface side electrode material paste 19a on the semiconductor substrate 11. The pattern of the side electrode material paste 19 a is transferred to the semiconductor substrate 11. By adopting such a technique, the pattern of the light receiving surface side electrode 19, that is, the thin and thick surface silver grid electrode 23 and the surface silver bus electrode 25 is formed as in the case of the first embodiment. And the step of placing the formed pattern on the semiconductor substrate 11 are separated.

  In the former process, the pattern of the light receiving surface side electrode material paste 19a is formed on the base film 31 having a smooth surface, which is different from the semiconductor substrate 11 as in the case of the first embodiment. It is possible to form an electrode pattern in which a vertical shape without bleeding in the direction is maintained. Moreover, in the latter process, the semiconductor substrate 11 is not pressed while being traced with a screen plate or a roll plate, but the entire light receiving surface of the semiconductor substrate 11 is pressed uniformly. It can suppress and can aim at the improvement of a yield.

  In addition, the light receiving surface side electrode 19 can be efficiently formed by transferring the pattern of the light receiving surface side electrode material paste 19a from the base film 41 on which the pattern of the light receiving surface side electrode material paste 19a has been previously formed. Moreover, the transfer of the pattern of the light-receiving surface side electrode material paste 19a can be performed with a simple apparatus and a simple process, and an electrode can be formed efficiently. And since there is no direct printing process with respect to the semiconductor substrate 11, the apparatus for printing and drying in a manufacturing line becomes unnecessary, and the electrode formation cost can be reduced significantly.

  And in the manufacturing method of the photovoltaic cell concerning Embodiment 2, the pattern of the light-receiving surface side electrode material paste 19a is peeled from the 1st base film 41a with the 2nd base film 41b, and the reflection prevention of the surface of the semiconductor substrate 11 is carried out. The pattern of the light-receiving-surface-side electrode material paste 19a is applied with a smaller pressure than in the first embodiment by adjusting the adhesive strength between the first base film 41a and the second base film 41b for transfer onto the film 17. Can be transferred onto the antireflection film 17, and the labor of the transfer process can be saved.

  Moreover, in the manufacturing method of the photovoltaic cell according to the second embodiment, the first base film 41a can be recycled after undergoing a process such as cleaning, and resource saving and cost reduction can be achieved. it can.

  Therefore, in the method for manufacturing a solar battery cell according to the second embodiment, the thin and thick surface silver grid electrode 23 and the surface silver bus electrode 25 are used as the light receiving surface side electrode 19 as in the case of the first embodiment. It can be produced efficiently, simply and inexpensively. And a photovoltaic cell with a large light receiving area and excellent photoelectric conversion efficiency can be produced efficiently, simply and inexpensively.

  As described above, the method for forming an electrode of a solar cell according to the present invention is useful when forming an electrode of a solar cell having a fine pattern easily and inexpensively.

DESCRIPTION OF SYMBOLS 1 Solar cell 11 Semiconductor substrate 11a p-type polycrystalline silicon substrate 13 p-type polycrystalline silicon layer 15 n-type impurity diffusion layer 17 Antireflection film 19 Light-receiving surface side electrode 19a Light-receiving surface-side electrode material paste 21 Back surface-side electrode 21a Back surface side Electrode material paste 23 Table silver grid electrode 25 Table silver bus electrode 31 Base film 32 Delivery roll 33 Sub roll 34 Winding roll 35 Stage 36 Stamper 41 Base film 41a First base film 41b Second base film

Claims (4)

A method for forming an electrode of a solar cell, wherein an electrode is formed on an electrode forming surface of a semiconductor substrate,
The electrode pattern in the sheet-like base material in which the electrode pattern is formed on one surface side by the electrode material is opposed to the electrode formation surface in the semiconductor substrate and aligned with the electrode formation position on the electrode formation surface. 1 process,
By pressing the entire region including the electrode pattern in the sheet-like base material uniformly, one surface side of the sheet-like base material is pressed against the electrode forming surface of the semiconductor substrate, and the electrode pattern is changed to the semiconductor A second step of transferring to the electrode forming surface of the substrate;
A third step of separating the sheet-like base material from the electrode forming surface of the semiconductor substrate;
A fourth step of firing the electrode pattern transferred to the semiconductor substrate to form the electrode on an electrode formation surface of the semiconductor substrate;
A method for forming an electrode of a solar cell, comprising: In the second step, pressing one surface side of the sheet-like base material to the electrode forming surface of the semiconductor substrate while heating the semiconductor substrate;
The method for forming an electrode for a solar cell according to claim 1. The sheet-like base material is a first sheet-like base material, and a second sheet-like shape in which the electrode pattern is formed on one side and the electrode pattern is on the outer side. A substrate and a laminated structure in which the substrate is laminated;
In the second step, transferring the electrode pattern together with the second sheet-like base material to the electrode forming surface of the semiconductor substrate;
The method for forming an electrode for a solar cell according to claim 1. A first step of forming an impurity diffusion layer in which an impurity element of the second conductivity type is diffused on one surface side of the first conductivity type semiconductor substrate;
A second step of forming an antireflection film on the impurity diffusion layer;
The pattern of the light receiving surface side electrode is formed on one surface side with an electrode material, and the pattern of the light receiving surface side electrode is opposed to the antireflection film and the light receiving surface side electrode is formed on the antireflection film. A third step of aligning with the position;
A pattern of the light-receiving surface side electrode is formed by pressing one surface side of the sheet-shaped base material against the antireflection film by uniformly pressing the entire region including the pattern of the light-receiving surface side electrode in the sheet-like base material. A fourth step of transferring the film onto the antireflection film;
A fifth step of separating the sheet-like substrate from the antireflection film;
A sixth step of arranging a pattern of the back side electrode with an electrode material on the other side of the semiconductor substrate;
The light receiving surface side electrode pattern and the back surface side electrode pattern are baked to form the light receiving surface electrode that penetrates the antireflection film and is electrically connected to the impurity diffusion layer, and the back surface side electrode. A seventh step;
The manufacturing method of the solar cell characterized by including.

Images