JP4610630B2 - Method for producing diffusion layer for solar cell and method for producing solar cell - Google Patents

Description

  The present invention relates to a method for producing a solar cell diffusion layer and a method for producing a solar battery cell.

  In a general crystalline silicon solar cell, it is necessary to form a pn junction in order to separate carriers generated by irradiation with sunlight. For example, when p-type silicon is used for the substrate, an n-type silicon layer is diffused by diffusing Group 5 elements such as phosphorus on the light-receiving surface side, or when n-type silicon is used for the substrate, boron or the like is used on the light-receiving surface side. A p-type silicon layer is formed by diffusing the group 3 element. A normal polycrystalline silicon solar cell uses p-type silicon as a substrate, and thermally diffuses a phosphorus-based dopant at a temperature of about 700 ° C. to 1000 ° C. to form a diffusion layer on both surfaces of the substrate. Then, unnecessary portions of the diffusion layer are removed to form a diffusion layer for solar cells.

  Then, for example, a silicon nitride film is formed on the diffusion layer as an antireflection film, and a grid-like silver paste is printed on the light-receiving surface side, and an aluminum paste electrode is printed and fired on the back surface to form a silicon crystal system. A solar cell can be formed. In some cases, the n-type diffusion layer on the back surface side is not removed, and the aluminum diffusion from the aluminum paste electrode is forcibly reversed to the p + layer of high concentration aluminum diffusion.

  Here, in order to increase the photoelectric conversion efficiency of the solar cell, it is preferable that the thickness of the diffusion layer is thin, but if it is too thin, the n-layer portion is likely to be broken by an electrode that is said to penetrate, and the high resistance is high. As a result, current collection at the electrode portion becomes impossible. Therefore, a structure called a selective emitter is preferable, in which the light receiving surface portion is a high resistance layer (low concentration diffusion) with a thin diffusion layer and the electrode portion is a low resistance layer (high concentration diffusion) with a thick diffusion layer. . However, in order to form this selective emitter by the conventional technique, a complicated process combining a plurality of times of diffusion and partial etching by masking is required.

  In view of this, there has been proposed a method of forming a selective emitter structure by applying an ink jet apparatus while partially changing the dopant concentration and performing a single heat treatment or partial laser irradiation (for example, Patent Document 1). , See Patent Document 2). As a result, the selective emitter structure can be easily manufactured, and the amount of chemicals sprayed unnecessarily can be reduced by performing ink-jet coating, so that the amount of dopant used can be reduced and the final manufacturing cost can be greatly reduced. .

  Further, instead of selective coating, a method of using a mask in an area where diffusion is desired to be restricted is conceivable. For example, a method of restricting dopant diffusion using a print formation mask (see, for example, Patent Document 3), and a similar technique include a mask. There has been reported a circuit board manufacturing method in which a hydrophobic resin film is used as a material, unnecessary portions are removed by laser irradiation, and a mask pattern is formed (see, for example, Patent Document 4).

  At the time of coating diffusion using an ink jet apparatus, it is desirable to perform coating diffusion after performing a process called gettering for removing impurities in the silicon substrate in order to improve the characteristics of the solar cell. In this gettering process, phosphorus diffusion is usually performed on both sides or one side of the substrate at an appropriate diffusion concentration, unnecessary heavy metal impurities such as iron are segregated in the diffusion layer portion, and the electron lifetime as an emitter of the silicon substrate is increased. When the heavy metal concentration is high, it is necessary to remove the diffusion layer in which the heavy metal impurities are segregated.

  Therefore, after performing double-sided diffusion corresponding to the high-resistance layer in a normal diffusion furnace, or after applying gettering diffusion by applying phosphoric acid on both sides or one side by inkjet coating, the low-resistance region by inkjet again It is conceivable to form a selective emitter structure by applying phosphoric acid only and additionally diffusing.

JP 2003-224285 A JP 2005-506705 gazette JP 2003-209271 A JP-A-7-115276

  However, once the diffusion process is performed and phosphoric acid glass is formed on the entire surface, phosphoric acid is coated on the phosphoric acid, the affinity between phosphorous glass and phosphoric acid is very good. There is a problem that the film spreads quickly and cannot be applied to a specific narrow area. Further, if the phosphorous glass layer is removed in order to suppress wetting and spreading, the electron lifetime in the region other than the coated portion is significantly reduced by diffusion baking after coating. This is because, in the presence of a phosphorous glass layer, high concentration of phosphorous is present at the interface with the silicon substrate, so that gettering of heavy metal impurities is performed efficiently and halfway oxidation is suppressed on the surface of the diffusion layer. This is probably because surface recombination is suppressed. Therefore, in order to improve the characteristics of the solar cell, it is necessary to perform diffusion heat treatment with the phosphor glass attached to the region other than the phosphoric acid application region to additionally form a low resistance layer. On the other hand, when a low resistance diffusion is performed by applying phosphoric acid or a phosphoric acid solution from above the phosphorus glass layer, the phosphorus glass layer serves as a mask, and the progress of diffusion is suppressed.

  The present invention has been made in view of the above, and a solar cell diffusion layer that can easily form a solar cell diffusion layer using a selective emitter by selective application of a dopant onto phosphorous glass. It aims at obtaining the manufacturing method of this, and the manufacturing method of a photovoltaic cell.

  In order to solve the above-described problems and achieve the object, a method for manufacturing a diffusion layer for a solar cell according to the present invention includes a phosphorus diffusion layer in which phosphorus is diffused and a phosphor glass layer in this order on a substrate surface. A water repellent layer forming step of forming a water repellent layer by applying a water repellent to the surface of the phosphorous glass layer of the substrate; and applying a laser to the silicon substrate on which the water repellent layer is formed to give a predetermined A removal step of removing the water repellent layer in the pattern region and at least a part of the phosphor glass layer, and applying the phosphoric acid or phosphoric acid solution to the surface of the silicon substrate subjected to the laser irradiation, the predetermined pattern A selective coating step of selectively coating the phosphoric acid or the phosphoric acid solution on the region, and heat-treating the silicon substrate coated with the phosphoric acid or the phosphoric acid solution, thereby the phosphoric acid or the phosphoric acid Phosphorus of the solution, characterized in that it comprises a low-resistance diffusion layer forming step of forming at least the phosphorus diffusion layer resistance diffusion layer by diffusing a part of, a.

  According to the present invention, there is an effect that it is possible to easily manufacture a solar cell diffusion layer using a selective emitter by selective application of phosphoric acid onto phosphorous glass, which is difficult with the conventional method.

  EMBODIMENT OF THE INVENTION Below, embodiment of the manufacturing method of the diffusion layer for solar cells concerning this invention and the manufacturing method of a photovoltaic 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. Moreover, in the following drawings, the scale between each member may differ from an actual thing for easy understanding. The same applies to the drawings.

Embodiment A method for manufacturing a solar cell diffusion layer according to the present embodiment includes a phosphorous diffusion layer on which phosphorus is diffused and a phosphorous glass layer on the surface of the phosphorous glass layer of the silicon substrate in this order. A water repellent layer forming step of forming a water repellent layer by applying an agent; and a silicon substrate on which the water repellent layer is formed is irradiated with a laser to form a water repellent layer in a predetermined pattern region and at least phosphorus A removing process for removing a part of the glass layer, and a selective coating process for selectively applying phosphoric acid or a phosphoric acid solution to a predetermined pattern region by applying a phosphoric acid or a phosphoric acid solution to the surface of a silicon substrate subjected to laser irradiation. And heat-treating the silicon substrate coated with phosphoric acid or phosphoric acid solution to diffuse the phosphoric acid or phosphorous in the phosphoric acid solution into at least part of the phosphorus diffusion layer to form a low resistance diffusion layer. A scattering layer forming step.

  Moreover, the manufacturing method of the diffusion layer for solar cells according to the present embodiment includes a step of forming a low resistance diffusion layer by the method for manufacturing a diffusion layer for solar cells according to the above-described embodiment, a water repellent layer, The process of removing the phosphorus glass layer, the process of forming an antireflection film on the phosphorus diffusion layer, and the electrode paste is disposed on the surface of the low resistance diffusion layer and the surface opposite to the surface of the low resistance diffusion layer after the antireflection film is formed And a step of baking an electrode paste to form an electrode.

  FIGS. 1-1 to 1-3 are diagrams illustrating a schematic configuration of a solar battery cell 1 manufactured by a method for manufacturing a diffusion layer for a solar battery and a method for manufacturing a solar battery cell according to an embodiment of the present invention. 1-1 is a cross-sectional view of the solar cell 1, FIG. 1-2 is a top view of the solar cell 1 viewed from the light receiving surface side, and FIG. 1-3 is the solar cell 1 viewed from the side opposite to the light receiving surface. FIG. 1-1 is a cross-sectional view taken along line AA in FIG. 1-3.

  As shown in FIGS. 1-1 to 1-3, the solar cell 1 includes a p-type silicon substrate 11 as a semiconductor substrate and an n-type diffusion layer in which the conductivity type of the surface of the p-type silicon substrate 11 is reversed ( (Phosphorus diffusion layer) 13, low resistance diffusion layer 19 having a lower resistance than n-type diffusion layer (phosphorus diffusion layer) 13, and p + layer (also referred to as BSF (Back Surface Field)) 12 containing a high concentration impurity. A semiconductor layer portion 10 having a photoelectric conversion function, an antireflection film 14 provided on the n-type diffusion layer (phosphorus diffusion layer) 13 to prevent reflection of incident light on the light receiving surface, and a semiconductor layer portion A surface silver grid electrode 15 provided locally on the light receiving surface for collecting electricity generated at 10 and a surface silver grid electrode 15 for taking out the electricity collected by the surface silver grid electrode 15. A front silver bus electrode 16 provided as Almost the entire back surface of the semiconductor layer portion 10 (surface facing the light receiving surface provided with the n-type diffusion layer (phosphorus diffusion layer) 13) for the purpose of extracting electricity generated by the body layer portion 10 and reflecting incident light. And a back silver electrode 18 for collecting electricity generated in the back aluminum electrode 17. The front silver grid electrode 15 and the front silver bus electrode 16 are collectively referred to as a front silver electrode (upper electrode). The back aluminum electrode 17 and the back silver electrode 18 constitute a lower electrode. Further, the low resistance diffusion layer 19 is formed in a shape substantially the same as the electrode pattern of the surface silver electrode and surrounded by the n-type diffusion layer (phosphorus diffusion layer) 13 in the lower region of the surface silver electrode.

  In the solar cell 1 configured as described above, sunlight is applied to the pn junction surface (the junction surface between the p-type silicon substrate and the n-type diffusion layer) of the semiconductor layer portion 10 from the light receiving surface side of the solar cell 1. Then, holes and electrons are generated. Due to the electric field at the pn junction, the generated electrons move toward the n-type diffusion layer 13 and the holes move toward the p + layer 12. As a result, an excess of electrons in the n-type diffusion layer 13 and an excess of holes in the p + layer 12 result in the generation of photovoltaic power. This photovoltaic power is generated in the direction in which the pn junction is forward-biased, the front silver bus electrode 16 connected to the n-type diffusion layer 13 becomes a negative pole, and the back silver electrode 18 connected to the p + layer 12 becomes a positive pole. Thus, a current flows through an external circuit (not shown).

Below, an example of the manufacturing method of such a photovoltaic cell 1 is demonstrated. First, as shown in FIG. 2A, a p-type silicon substrate 11 subjected to surface treatment is prepared. Next, as shown in FIG. 2B, an n-type diffusion layer (phosphorus diffusion layer) 13 a whose conductivity type is reversed by thermally diffusing phosphorus is formed on the surface layer of the p-type silicon substrate 11. Usually, phosphorus oxychloride (POCl ₃ ) is used as a phosphorus diffusion source. At this time, a phosphorus glass layer 21 a is formed on the outermost surface of the p-type silicon substrate 11.

  Next, after protecting one main surface of the p-type silicon substrate 11 with a resist, the phosphor glass layer 21 and the n-type diffusion layer (phosphorus diffusion layer) 13 are left only on one main surface as shown in FIG. Then, the surface of the p-type silicon substrate 11 is etched, and the resist is removed using an organic solvent or the like.

  Next, as shown in FIG. 2-4, a water repellent layer 22 is formed by applying a water repellent agent on the phosphor glass layer 21. As the water repellent, for example, a silicone-based water repellent can be used. By using a silicone-based coating agent as the water repellent, there is no adverse effect on the solar cell characteristics due to the water repellent, and the deterioration of the solar cell characteristics due to the use of the water repellent can be prevented.

  Next, laser irradiation is performed on the surface of the p-type silicon substrate 11 on which the water repellent layer 22 is formed, and the water repellent layer 22 and the phosphorous glass layer 21 are etched as shown in FIG. The liquid medicine layer 22 and the phosphorus glass layer 21 are removed. Laser irradiation is performed only on a portion of the surface of the p-type silicon substrate 11 on which the water repellent layer 22 is formed, which is a formation region of the low resistance diffusion layer 19 corresponding to the electrode pattern of the surface silver electrode. The phosphorus glass layer 21 may be left in a very thin state.

  When inkjet coating of phosphoric acid is performed on the surface of the p-type silicon substrate 11 with the phosphorous glass layer 21 formed thereon, the affinity between the phosphorous glass layer 21 and phosphoric acid is very good. The acid quickly wets and spreads, and limited application to a specific narrow area is impossible. Further, if the phosphorous glass layer 21 is removed in order to suppress wetting and spreading, the electron lifetime in the region other than the coated portion is significantly reduced by diffusion baking after coating. On the other hand, when low resistance diffusion is performed by applying phosphoric acid or a phosphoric acid solution from above the phosphorous glass layer 21, the phosphorous glass layer 21 serves as a mask, and the progress of diffusion is suppressed.

  Therefore, there is no phosphor glass layer 21 in a region where low resistance diffusion of phosphorus is desired, or it exists in a very thin state, and phosphoric acid or phosphoric acid solution is applied only to this region, and other regions are coated. Is preferably in a state in which a phosphorus glass layer 21 as a protective layer is present. Therefore, in the present embodiment, laser irradiation is performed only on the portion where the low resistance diffusion layer 19 is to be formed, and the water repellent layer 22 and the phosphor glass layer 21 in this portion are removed.

  For laser irradiation, a laser such as an infrared laser, a visible light laser, or an ultraviolet laser can be used. By performing laser irradiation, the process of removing all or part of the water repellent layer 22 and the phosphorus glass layer 21 is facilitated.

  For example, a YAG fundamental wave can be used as the laser beam, but if the damage to the p-type silicon substrate 11 is small and the phosphorus glass layer 21 can be removed to some extent, the YAG second harmonic, the third harmonic, etc. Any other wavelength may be used. In general, the longer the laser wavelength, the greater the amount of energy transmitted to the p-type silicon substrate 11 side, so that damage to the phosphorus diffusion layer and the substrate side is likely to occur. As the wavelength of the laser is shorter, absorption at the water repellent layer 22 and the phosphor glass layer 21 portion is preferential, and these can be selectively removed, but the laser device becomes expensive.

  Next, as shown in FIG. 2-6, phosphoric acid 23 is applied to the p-type silicon substrate 11 from which the water repellent layer 22 has been removed and the phosphorous glass layer 21 has been etched by laser irradiation. Alternatively, a phosphoric acid solution is applied. As a coating method, any one of roller coating, spray coating, dip coating, and inkjet coating, or a combination thereof may be used as long as the phosphoric acid 23 or the phosphoric acid solution can be coated. By using these methods, it becomes easy to apply phosphoric acid 23 or a phosphoric acid solution which is a dopant material.

  Here, since the water repellent layer 22 exists in the p-type silicon substrate 11 other than the laser irradiated portion and the water repellent layer 22 repels the phosphoric acid 23 or the phosphoric acid solution, basically only the laser irradiated portion is present. The phosphoric acid 23 or the phosphoric acid solution is selectively attached to the surface. Further, when the phosphoric acid 23 or the phosphoric acid solution droplets remain in the region where the water repellent layer 22 exists, the droplets can be easily removed by air blowing or wiping.

  As the phosphoric acid solution, an aqueous solution of phosphoric acid or an alcohol solution can be used. In a high-concentration solution, since the viscosity is large and it may be difficult to separate the coating depending on the presence or absence of the water repellent layer 22, it is appropriately diluted with a solvent such as water or alcohol to obtain a phosphoric acid solution. In particular, when applying by ink jet, the viscosity and surface tension can be adjusted by using an alcohol solution, and ink jet discharge becomes possible. Usually, in order to perform stable inkjet discharge, it is preferable that the viscosity is 10 (mPa · s) or less and the surface tension is 50 (mN / m) or less. Further, when it is desired to reduce the required sheet resistance of the diffusion layer, a high concentration solution may be used. When it is desired to increase the sheet resistance, a low concentration solution may be used. Moreover, if it is a liquid, phosphorus type diffusing agents other than phosphoric acid can also be used.

  Next, the p-type silicon substrate 11 to which the phosphoric acid 23 or the phosphoric acid solution is applied is heat-treated, thereby adding an n-type diffusion layer (phosphorus diffusion layer) 13 corresponding to the region to which the phosphoric acid 23 or the phosphoric acid solution is applied. Reduce resistance by diffusion. As heat processing temperature, 700 to 1000 degreeC is preferable. Thereby, the low resistance diffusion layer 19 is formed. Further, the n-type diffusion layer (phosphorus diffusion layer) 13 corresponding to the region where the phosphoric acid or the phosphoric acid solution is not applied also causes additional diffusion of phosphorus by the heat treatment. There is little decrease in sheet resistance as compared with the portion coated with.

  The general trend for the formation of n-type diffusion layers (phosphorus diffusion layers) is to increase the concentration of phosphoric acid or phosphoric acid solution, increase the coating amount, increase the diffusion temperature, and increase the diffusion time. The n-type diffusion layer (phosphorus diffusion layer) is thick and has a high concentration, and the sheet resistance is low. Conversely, by lowering the phosphoric acid or phosphoric acid concentration in the phosphoric acid or phosphoric acid solution, reducing the coating amount, lowering the diffusion temperature, and shortening the diffusion time, the phosphoric acid or phosphoric acid solution becomes thinner and lower in concentration. Resistance increases. In general, the sheet resistance of the electrode region is about 30 to 50 Ω / □, and the sheet resistance of the light receiving surface is about 60 to 120 Ω / □, thereby functioning as a diffusion layer for the selective emitter.

  The p-type silicon substrate 11 subjected to the heat treatment has a phosphorous glass layer formed on the surface along with the formation of the low-resistance diffusion layer 19. The glass layer, the water repellent layer 22 and the phosphorus glass layer 21 are removed, and the low resistance diffusion layer 19 and the n-type diffusion layer (phosphorus diffusion layer) 13 are exposed. Thereby, a selective emitter diffusion layer having the low resistance diffusion layer 19 and the n-type diffusion layer (phosphorus diffusion layer) 13 is obtained.

  Next, an antireflection film 14 made of a silicon oxide film, a silicon nitride film, a titanium oxide film or the like is formed on the surface of the n-type diffusion layer (phosphorus diffusion layer) 13 by a film forming method such as a plasma CVD (Chemical Vapor Deposition) method. , With a uniform thickness. The antireflection film 14 also functions as a passivation film.

  Further, the surface silver grid electrode pattern and the surface silver bus electrode pattern are screen-printed with a silver paste on the low resistance diffusion layer 19 and dried at 100 ° C. to 300 ° C. Electrode 16 is formed (before firing). Next, a pattern of a back aluminum electrode and a back silver electrode is screen-printed on the back surface side of the p-type silicon substrate 11, dried at 100 ° C. to 300 ° C., and then fired at 700 ° C. to 1000 ° C. And the p + layer 12 are formed, and at the same time, the surface silver grid electrode is fired.

  Through the above steps, the solar battery cell 1 using the selective emitter can be easily manufactured. Generally, a solar cell using a selective emitter can obtain a conversion efficiency that is about 0.3 to 1% higher than that of a normal solar cell made of a uniform diffusion layer.

  As described above, according to the method for manufacturing a solar cell diffusion layer according to the present embodiment, the phosphorus glass layer 21 of the p-type silicon substrate 11 having the phosphorus glass layer 21 and the n-type diffusion layer (phosphorus diffusion layer) 13. After forming a water repellent layer 22 by applying a water repellent agent thereon, the water repellent layer 22 and the phosphor glass layer 21 are removed by laser irradiation, and phosphoric acid 23 or a phosphoric acid solution is applied to the laser irradiated portion. After that, the p-type silicon substrate 11 is heat-treated. Thereby, formation of the diffusion layer for solar cells using the selective emitter can be easily realized by selective application of phosphoric acid on the phosphor glass, which is difficult with the conventional ink jet coating method.

  In addition, according to the method for manufacturing a solar battery cell according to the present embodiment, the diffusion for solar battery using a selective emitter can be achieved by selective application of phosphoric acid on phosphorus glass, which is difficult with the conventional ink jet coating method. It is possible to form a solar cell having a high conversion efficiency by forming a layer.

  Hereinafter, the manufacturing method of the diffusion layer for solar cells and the manufacturing method of the solar battery cell according to the present embodiment will be specifically described by way of examples.

Example 1.
Prepare a p-type polycrystalline silicon substrate on which the n-type diffusion layer having a sheet resistance of 80Ω / □ to 100Ω / □ is formed on the substrate surface, and the phosphor glass layer formed on the outermost surface of the substrate is not removed. As a silicone-based water repellent, 1 wt% to 10 wt% xylene solution of dimethyl silicone oil was applied by spin coating. And it dried at the temperature of 100 to 250 degreeC, and formed the water repellent layer on the phosphorus glass layer.

  The p-type polycrystalline silicon substrate on which the water repellent layer is formed is irradiated with a YAG fundamental wave laser only in a region where a grid electrode having a line width of 100 μm to 200 μm and a bus electrode having a line width of 1 mm to 3 mm are formed. Then, the water repellent layer and the phosphorus glass layer were removed. Regarding the phosphorous glass layer, the laser irradiation conditions were generally adjusted so that 70% to 90% of the glass could be removed.

  As a phosphoric acid solution, phosphoric acid (85 wt% or more) was diluted with water to prepare a 30 wt% to 60 wt% phosphoric acid aqueous solution. The phosphoric acid aqueous solution was adhered only to the laser irradiated portion by immersing and pulling up the p-type polycrystalline silicon substrate that had been irradiated with the laser in the phosphoric acid aqueous solution. In addition, air blowing was performed to remove droplets of the phosphoric acid aqueous solution adhering to the water repellent layer portion. The p-type polycrystalline silicon substrate coated with the phosphoric acid aqueous solution was heat-treated in dry air or nitrogen at 700 ° C. to 900 ° C. to perform phosphorus diffusion treatment to form a low resistance diffusion layer.

  Subsequently, cleaning with hydrofluoric acid was performed to remove all the phosphorus glass layer on the surface. At this time, the sheet resistance of the electrode region (low resistance diffusion layer) was 35Ω / □ to 40Ω / □, and the sheet resistance of the light receiving surface (n-type diffusion layer) was 80Ω / □ to 90Ω / □.

  An SiN film serving as an antireflection film and passivation film was formed on the n-type diffusion layer on the p-type polycrystalline silicon substrate on which the selective emitter diffusion layer was formed in this manner. Furthermore, the pattern of the surface silver grid electrode and the pattern of the surface silver bus electrode were screen-printed with a silver paste on the low resistance diffusion layer, and dried at 100 ° C. to 300 ° C.

  Next, the back aluminum electrode pattern and the back silver electrode pattern were screen-printed on the back side of the p-type polycrystalline silicon substrate, and dried at 100 ° C. to 300 ° C. Next, by baking at 700 ° C. to 1000 ° C., a back aluminum electrode was formed and a p + layer was formed, and at the same time, a front silver electrode was fired. Thus, a solar battery cell having a selective emitter was formed.

  As the solar cell output characteristics of this solar cell, when photoelectric conversion efficiency (%) was measured and evaluated, the efficiency is about 0.5% to 1% higher than that of a normal solar cell having a uniform n-type diffusion layer. Conversion efficiencies of 16% to 17% were obtained.

  Therefore, in Example 1, by using the method for manufacturing a solar cell diffusion layer and the method for manufacturing a solar cell according to the embodiment, the solar cell having a selective emitter and having good light conversion efficiency. Could get.

Example 2
Prepare a p-type polycrystalline silicon substrate on which the n-type diffusion layer having a sheet resistance of 80Ω / □ to 100Ω / □ is formed on the substrate surface, and the phosphor glass layer formed on the outermost surface of the substrate is not removed. As a silicone-based water repellent, 1 wt% to 10 wt% xylene solution of dimethyl silicone oil was applied by spin coating. And it dried at the temperature of 100 to 250 degreeC, and formed the water repellent layer on the phosphorus glass layer.

  The p-type polycrystalline silicon substrate on which the water repellent layer is formed is irradiated with a YAG fundamental wave laser only in a region where a grid electrode having a line width of 100 μm to 200 μm and a bus electrode having a line width of 1 mm to 3 mm are formed. Then, the water repellent layer and the phosphorus glass layer were removed. Regarding the phosphorous glass layer, the laser irradiation conditions were generally adjusted so that 70% to 90% of the glass could be removed.

  As a phosphoric acid solution, phosphoric acid (85 wt% or more) was diluted with ethanol to prepare a 10 wt% to 30 wt% phosphoric alcohol solution. This phosphoric alcohol solution was selectively applied to the laser irradiated portion of the p-type polycrystalline silicon substrate using an ink jet apparatus. Since the water-repellent agent is applied to the portions other than the laser irradiated portion, the phosphoric alcohol solution does not spread and spread. The p-type polycrystalline silicon substrate coated with the phosphate alcohol solution in this manner was heat-treated in dry air or nitrogen at 700 ° C. to 900 ° C. to perform phosphorus diffusion treatment, thereby forming a low resistance diffusion layer.

  Subsequently, cleaning with hydrofluoric acid was performed to remove all the phosphorus glass layer on the surface. At this time, the sheet resistance of the electrode region (low resistance diffusion layer) was 35Ω / □ to 40Ω / □, and the sheet resistance of the light receiving surface (n-type diffusion layer) was 80Ω / □ to 90Ω / □.

  An SiN film serving as an antireflection film and passivation film was formed on the n-type diffusion layer on the p-type polycrystalline silicon substrate on which the selective emitter diffusion layer was formed in this manner. Furthermore, the pattern of the surface silver grid electrode and the pattern of the surface silver bus electrode were screen-printed with a silver paste on the low resistance diffusion layer, and dried at 100 ° C. to 300 ° C.

  Next, the back aluminum electrode pattern and the back silver electrode pattern were screen-printed on the back side of the p-type polycrystalline silicon substrate, and dried at 100 ° C. to 300 ° C. Next, by baking at 700 ° C. to 1000 ° C., a back aluminum electrode was formed and a p + layer was formed, and at the same time, a front silver electrode was fired. Thus, a solar battery cell having a selective emitter was formed.

  As the solar cell output characteristics of this solar cell, when photoelectric conversion efficiency (%) was measured and evaluated, the efficiency is about 0.5% to 1% higher than that of a normal solar cell having a uniform n-type diffusion layer. Conversion efficiencies of 16% to 17% were obtained.

  Therefore, in Example 2, by using the method for manufacturing a solar cell diffusion layer and the method for manufacturing a solar cell according to the embodiment, a solar cell having a selective emitter and having good light conversion efficiency. Could get.

  As described above, the method for manufacturing a solar cell diffusion layer according to the present invention is useful for manufacturing a solar cell diffusion layer having a selective emitter structure.

It is sectional drawing which shows schematic structure of the photovoltaic cell concerning embodiment of this invention. It is a bottom view which shows schematic structure of the photovoltaic cell concerning embodiment of this invention. It is a top view which shows schematic structure of the photovoltaic cell concerning embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Solar cell 11 Semiconductor layer part 12 p-type silicon substrate 13 n-type diffusion layer (phosphorus diffusion layer)
14 Antireflective coating 15 Front silver grid electrode 16 Front silver bus electrode 17 Back aluminum electrode 18 Back silver electrode 19 Low resistance diffusion layer 21a Phosphorus glass layer 21 Phosphorus glass layer 22 Water repellent layer 23 Phosphoric acid

Claims (5)

A water repellent layer forming step of forming a water repellent layer by applying a water repellent to the surface of the phosphor glass layer of a silicon substrate having a phosphorous diffusion layer and a phosphorous glass layer in this order on the substrate surface. When,
A removal step of removing a part of the water repellent layer and at least part of the phosphor glass layer in a predetermined pattern region by irradiating a laser on the silicon substrate on which the water repellent layer is formed;
A selective coating step in which phosphoric acid or a phosphoric acid solution is applied to the surface of the silicon substrate that has been subjected to the laser irradiation, and the phosphoric acid or the phosphoric acid solution is selectively applied to the predetermined pattern region;
By heat-treating the silicon substrate coated with the phosphoric acid or the phosphoric acid solution, phosphorus in the phosphoric acid or the phosphoric acid solution is diffused into at least a part of the phosphorus diffusion layer to form a low resistance diffusion layer. A low resistance diffusion layer forming step;
The manufacturing method of the diffusion layer for solar cells characterized by including. Using a silicone-based coating agent as the water repellent;
The manufacturing method of the diffusion layer for solar cells of Claim 1 characterized by these. The laser irradiation is performed using at least one of an infrared laser, a visible light laser, and an ultraviolet laser;
The manufacturing method of the diffusion layer for solar cells of Claim 1 or 2 characterized by these. Application of the water repellent is performed by any one of roller application, spray application, dip application, and ink jet application, or a combination thereof.
The manufacturing method of the diffusion layer for solar cells as described in any one of Claims 1-3 characterized by these. Forming the low-resistance diffusion layer by the method for manufacturing a solar cell diffusion layer according to any one of claims 1 to 4,
Removing the water repellent layer and the phosphorous glass layer;
Forming an antireflection film on the phosphorus diffusion layer;
Arranging an electrode paste on the surface opposite to the low resistance diffusion layer surface and the low resistance diffusion layer surface after forming the antireflection film;
Baking the electrode paste to form an electrode;
The manufacturing method of the photovoltaic cell characterized by including.

Images