JP2012204660A - Photovoltaic device, manufacturing method thereof, and photovoltaic module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photovoltaic device having a diffusion layer structure similar to a selective emitter structure capable of reducing connection resistance of a light reception face side electrode while increasing resistance of a light reception face, and excellent in photoelectric conversion efficiency.SOLUTION: A photovoltaic device comprises a first conductive type single crystal silicon substrate 1, on one face of which an uneven shape is formed; a plurality of first diffusion layers 2a that are dispersed at a peak part of a convex part of the uneven shape on an entire face on one side of the single crystal silicon substrate 1, and on which second conductive type impure elements are diffused at a first concentration; second diffusion layers 5 that are formed in a region other than the first diffusion layers 2a on one side of the single crystal silicon substrate 1, and on which the second conductive type impure elements are diffused at a second concentration lower than the first concentration; light reception face side electrodes 7 electrically connected to the first diffusion layers 2a and formed on one side of the single crystal silicon substrate 1; and a rear face side electrode 8 formed on the other side of the single crystal silicon substrate 1.

Description

  The present invention relates to a photovoltaic device, a manufacturing method thereof, and a photovoltaic module.

  In order to improve the performance of photovoltaic devices such as solar cells, it is important to efficiently incorporate sunlight into the substrate constituting the solar cells. For this reason, texture processing is performed on the substrate surface on the light incident side, and light once reflected on the substrate surface is incident again on the substrate surface, so that more sunlight is taken into the substrate and the photoelectric conversion efficiency is improved. ing. Here, the texture processing is processing for intentionally forming fine irregularities having dimensions of several tens of nanometers to several tens of micrometers on the substrate surface.

  As a method of texture formation on a substrate for solar cells, when the substrate is a single crystal substrate, anisotropic etching with an aqueous alkali solution such as sodium hydroxide or potassium hydroxide having a crystal orientation dependence on the etching rate is widely used. Used. For example, when this anisotropic etching is performed on the (100) substrate surface, a pyramidal texture with the (111) plane exposed is formed on the substrate surface.

  When a texture is formed on a single crystal substrate, an ideal inverted pyramid texture can be formed on the surface of the substrate by using an etching mask, and a method using an etching mask by a photoengraving method has been put into practical use. . However, the photoengraving method has drawbacks that the process cost is high and it is difficult to apply to a large substrate.

  Therefore, as a method for forming an etching mask that replaces photoengraving, for example, an etching mask film having an opening is formed on the surface of a silicon substrate, and a concave portion is formed in the mask opening by blasting the surface of the mask film. There has been proposed a method of forming a texture consisting of (see, for example, Patent Document 1).

  In addition, the method of forming an etching mask on the surface of the silicon substrate, blasting the mask surface to form an opening in the mask surface, and subsequently performing the etching process to form a texture. Inventors have proposed (for example, refer patent document 2).

  On the other hand, as a solar cell structure for increasing the photoelectric conversion efficiency, there is a selective emitter structure in which the impurity concentration in the other region on the light receiving surface side of the substrate is made lower than the impurity concentration just below the light receiving surface side electrode. In the selective emitter structure, since the impurity concentration directly under the light receiving surface side electrode is high, the contact resistance between the electrode and the silicon substrate can be reduced. Further, since the impurity concentration is low except for the electrode portion, the quantum efficiency on the short wavelength light side of the solar cell can be improved.

  In order to form such a selective emitter structure, for example, after forming a resist pattern on the light-receiving surface side of the substrate on which the silicon oxide film is formed, the silicon oxide film at the opening of the resist pattern is removed, and the light-receiving surface side Openings corresponding to the electrodes are formed in the silicon oxide film. Thereafter, by diffusing impurities, a high concentration diffusion layer is formed in the opening of the silicon oxide film, and a low concentration diffusion layer is formed in the other portion. And after electrode paste is printed according to a high concentration diffused layer, baking of electrode paste is performed and a light-receiving surface side electrode is formed (for example, refer to patent documents 3).

JP 2002-43601 A International Publication No. 2009/128324 JP 2004-193350 A

  However, according to the above conventional technique, there is a problem that the process becomes complicated because a resist mask printing process is required to form the selective emitter structure.

  Further, according to the above conventional technique, there is a problem that it is necessary to perform alignment in a region where a high-concentration diffusion layer is formed during electrode printing, which places a burden on the process.

  The present invention has been made in view of the above, and has a diffusion layer structure similar to a selective emitter structure capable of reducing the connection resistance of the light-receiving surface side electrode while increasing the resistance of the light-receiving surface, and improving the photoelectric conversion efficiency. It is an object of the present invention to obtain an excellent photovoltaic device, a manufacturing method thereof, and a photovoltaic module.

  In order to solve the above-described problems and achieve the object, a photovoltaic device according to the present invention includes a first-conductivity-type single-crystal silicon substrate having a concavo-convex shape formed on one side, and the single-crystal silicon substrate. A plurality of first diffusion layers which are dispersedly arranged on tops of the concavo-convex convex portions on the entire surface of the one surface side and in which a second conductivity type impurity element diffuses at a first concentration; and one surface side of the single crystal silicon substrate A second diffusion layer formed in a region other than the first diffusion layer, wherein the second conductivity type impurity element is diffused at a second concentration lower than the first concentration, and the first diffusion A light receiving surface side electrode electrically connected to the layer and formed on one surface side of the single crystal silicon substrate; and a back surface side electrode formed on the other surface side of the single crystal silicon substrate. To do.

  According to the present invention, a photovoltaic device having a diffusion layer structure similar to a selective emitter structure capable of reducing the connection resistance of the light receiving surface side electrode while increasing the resistance of the light receiving surface, and having excellent photoelectric conversion efficiency can be easily obtained. The effect is obtained.

FIG. 1-1 is a cross-sectional view of relevant parts for explaining the method of manufacturing a photovoltaic device according to the embodiment of the present invention. FIGS. 1-2 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic apparatus concerning embodiment of this invention. FIGS. 1-3 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic apparatus concerning embodiment of this invention. 1-4 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic apparatus concerning embodiment of this invention. FIGS. 1-5 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic apparatus concerning embodiment of this invention. FIGS. FIGS. 1-6 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic apparatus concerning embodiment of this invention. FIGS. FIGS. 1-7 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic apparatus concerning embodiment of this invention. FIGS. FIGS. 1-8 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic apparatus concerning embodiment of this invention. FIGS. FIGS. 1-9 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic apparatus concerning embodiment of this invention. FIGS. FIGS. 2-1 is principal part sectional drawing for demonstrating the manufacturing method of the selective emitter type photovoltaic apparatus using a resist pattern. FIGS. FIGS. 2-2 is principal part sectional drawing for demonstrating the manufacturing method of the selective emitter type photovoltaic device using a resist pattern. FIGS. FIGS. 2-3 is principal part sectional drawing for demonstrating the manufacturing method of the selective emitter type photovoltaic apparatus using a resist pattern. FIGS. 2-4 is principal part sectional drawing for demonstrating the manufacturing method of the selective emitter type photovoltaic apparatus using a resist pattern. FIGS. FIGS. 2-5 is principal part sectional drawing for demonstrating the manufacturing method of the selective emitter type photovoltaic apparatus using a resist pattern. FIGS. FIGS. 2-6 is principal part sectional drawing for demonstrating the manufacturing method of the selective emitter type photovoltaic device using a resist pattern. FIGS. FIGS. 2-7 is principal part sectional drawing for demonstrating the manufacturing method of the selective emitter type photovoltaic apparatus using a resist pattern. FIGS. FIGS. 2-8 is principal part sectional drawing for demonstrating the manufacturing method of the selective emitter type photovoltaic apparatus using a resist pattern. FIGS. FIGS. 2-9 is principal part sectional drawing for demonstrating the manufacturing method of the selective emitter type photovoltaic apparatus using a resist pattern. FIGS. FIG. 3A is a plan view schematically showing the state of the light receiving surface side of the substrate at the time when the second diffusion layer is formed in the method for manufacturing a photovoltaic device according to the embodiment of the present invention. . 3-2 is an enlarged view showing a part of FIG. 3-1. FIG. 4 is a plan view schematically showing the state of the light receiving surface side of the substrate at the time when the second diffusion layer is formed in the method of manufacturing the selective emitter type photovoltaic device using the resist pattern.

  Embodiments of a photovoltaic device, a manufacturing method thereof, and a photovoltaic module 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. Further, even a plan view may be hatched to make the drawing easy to see.

Embodiment FIGS. 1-1 to 1-9 are cross-sectional views of relevant parts for explaining a method of manufacturing a photovoltaic device according to an embodiment of the present invention. Hereinafter, a method for manufacturing the photovoltaic device according to the present embodiment will be described with reference to FIGS. First, in the first step, the first impurity diffusion layer 2a (hereinafter referred to as the first diffusion layer) is formed by diffusing impurities on the surface of the single crystal silicon substrate 1 (hereinafter sometimes referred to as the substrate 1). 2a) (FIG. 1-1).

  The single crystal silicon substrate 1 in the present embodiment is widely used for consumer solar cells. After slicing from a single crystal silicon ingot with a multi-wire saw, wet etching using an acid or alkali solution is performed. It removes damage when slicing. For example, the thickness of the substrate 1 after damage removal is 200 μm and the dimensions are 15 cm square. In addition, the dimension of the board | substrate 1 is not limited to this, It can change suitably.

  The polarity of the substrate 1 may be either p-type or n-type, and a pn junction is formed by forming a diffusion layer of the opposite type of the polarity of the substrate 1 as the first diffusion layer 2a. In general, phosphorous (P) is diffused when the first diffusion layer 2a is n-type, and boron (B) is diffused when the first diffusion layer 2a is p-type.

In the present embodiment, as an example, a p-type single crystal silicon substrate 1 having a specific resistance of 1 Ωcm to 3 Ωcm is used. The first diffusion layer 2a is an n-type impurity diffusion layer, and is a high concentration diffusion layer (low resistance region) in which phosphorus (P) is diffused at a first concentration. The substrate 1 is put into a thermal diffusion path, and the first diffusion layer 2a having a sheet resistance of, for example, 20Ω / □ to 40Ω / □ is formed by thermal diffusion of phosphorus (P) using phosphorus oxychloride (POCl ₃ ). . The sheet resistance of the first diffusion layer 2a is a value after formation of the second diffusion layer 5 described later.

  In the second step, a protective film 3a is deposited on the surface of the first diffusion layer 2a (FIGS. 1-2). As the protective film, a thermal oxide film formed by a thermal oxidation method in which an oxidation treatment is performed at a temperature of 800 ° C. to 1000 ° C., or about 400 ° C. to 700 ° C. by a normal pressure chemical vapor deposition (CVD) method. It is possible to use a low-temperature oxide film formed at this temperature, a silicon nitride film formed by a chemical deposition method such as plasma CVD, or a physical deposition method such as sputtering. Further, these films may be used in combination. In the thermal oxidation method, a protective film is formed on the entire surface of the substrate 1, but in the CVD method or the sputtering method, the film is usually formed on only one side, so that the film is formed on both sides as necessary. However, this does not apply when etching protection on the back side of the substrate is unnecessary.

In the third step, the protective film 3a formed on the light-receiving surface side (first diffusion layer 2a side) of the substrate 1 is subjected to blasting to form an opening 3b in the protective film 3a (FIG. 1-3). ). That is, a plurality of openings 3b are formed in the protective film 3a formed on the light receiving surface side (first diffusion layer 2a side) by blast processing. As the blasting, normal dry blasting in which abrasive powder such as alumina (Al ₂ O ₃ ), silicon carbide (SiC) or glass is blown with air, or abrasive such as alumina, silicon carbide (SiC) or glass is used. It is possible to use wet blasting or the like that sprays a mist in which granular powder is dispersed in water.

  Depending on the size of the abrasive grains used for the blast processing, the aperture diameter and aperture pitch of the apertures 3b change. For this blasting treatment, for example, abrasive grains of size # 500 to # 3000 can be used, and it is particularly preferable to use abrasive grains of size # 800 to # 2000. Thereby, a pyramid-shaped rough surface structure having a base length of about 10 μm to 30 μm can be formed in a later etching step. In addition, when formation of a rough surface structure is required on both surfaces, it is necessary to perform the said blasting process on both surfaces. Here, a case where a rough surface structure is formed only on the light receiving surface side of the substrate 1 will be described.

  In the fourth step, anisotropic etching is performed on one surface of the light-receiving surface side (first diffusion layer 2a side) of the substrate 1 using the protective film 3a in which the openings 3b are formed as a mask. The surface of the light receiving surface (the first diffusion layer 2a side) is roughened (FIGS. 1-4). As anisotropic etching, wet etching using an alkaline aqueous solution is performed under the condition that the protective film 3a has resistance.

  Any etching solution may be used as long as it dissolves silicon and has a small dissolving ability with respect to the protective film 3a. As such an etchant, for example, any one of an alkaline aqueous solution and an alkaline aqueous solution containing an additive such as isopropanol imparting etching anisotropy, or a combination thereof can be used. By using such an etching solution, it is possible to form a rough surface shape 4 having a concavo-convex shape called a random pyramid on the surface of the substrate 1. The size of the random pyramid at this time is determined by the aperture diameter and aperture pitch of the apertures 3b formed in the blast processing step as described above.

  In the etching, by controlling the etching conditions such as the concentration of the etching solution, the temperature of the etching solution, and the etching time, the etching progress state is controlled so that the unetched region 2b remains at the apex portion of the random pyramid. Such etching forms a rough surface shape 4 in which the concave portion reaches the inside of the substrate 1 and the unetched region 2b remains only at the apex portion of the random pyramid. The fine first diffusion layer 2a remaining without being etched remains only around the lower portion of the unetched region 2b and is distributed over the entire surface of the substrate 1 on the light receiving side.

  In the fifth step, the protective film 3a is removed by, for example, hydrofluoric acid to expose the rough surface shape 4 (FIGS. 1-5).

In the sixth step, the second impurity diffusion layer 5 (hereinafter referred to as the second diffusion layer 5), which is an n-type impurity diffusion layer, is formed on the light receiving surface side (first diffusion layer 2a side) of the substrate 1. (FIGS. 1-6). That is, the substrate 1 is put into a thermal diffusion path, and the second diffusion layer 5 having a sheet resistance of 80Ω / □ to 120Ω / □ is formed by thermal diffusion of phosphorus (P) using phosphorus oxychloride (POCl ₃ ), for example. Form. The thermal diffusion of phosphorus (P) is performed at a second concentration that is lower than the first concentration. Therefore, the second diffusion layer 5 is a low concentration diffusion layer (high resistance region) in which phosphorus (P) is diffused at a second concentration lower than the first concentration.

  Here, the second concentration is lower than the first concentration. For this reason, the second diffusion layer 5 which is a low concentration diffusion layer is formed only on the slope of the rough surface shape 4, and the first diffusion layer 2a remaining at the top of the random pyramid is directly used as the high concentration diffusion layer. It is said. The fine first diffusion layers 2a, which are high-concentration diffusion layers (low resistance regions), are distributed over the entire surface of the substrate 1 on the light receiving side.

  In the seventh step, an antireflection film 6 made of a silicon nitride film is formed, for example, by plasma CVD on the light receiving surface side (first diffusion layer 2a side) of the substrate 1 on which the rough surface shape 4 is formed (FIG. 1). -7). The silicon nitride film may be formed by other methods such as a sputtering method instead of the plasma CVD method.

  In the eighth step, a metal paste to be an electrode is applied to the substrate 1 by screen printing (FIGS. 1-8). On the front side (light-receiving surface side) of the substrate 1, for example, silver paste 7 a mixed with silver is applied in a comb shape in a grid electrode shape and a bus electrode shape with a line width of 100 μm. On the back side of the substrate 1, an aluminum paste 8a mixed with aluminum is applied to the entire surface by screen printing. In FIG. 1-8, only the silver paste 7a and the aluminum paste 8a applied to the grid electrode shape are shown.

  In the ninth step, the metal paste is fired to form the light-receiving surface side electrode 7 and the back surface electrode 8 (FIGS. 1-9). Firing is performed at 800 ° C. to 900 ° C. in an air atmosphere, for example. By baking, the silver paste 7a is solidified and corrodes the antireflection film 6, and electrical connection is formed with the first diffusion layer 2a and the second diffusion layer 5. At this time, since the electrode is formed in the rough surface shape 4, the contact area between the first diffusion layer 2a and the second diffusion layer 5 and the light receiving surface side electrode 7 is increased, and the connection resistance is reduced. At the same time, the mechanical connection strength increases. Thereafter, the shorted portion of the pn junction on the outer peripheral portion of the substrate 1 is removed by laser cutting. As described above, the photovoltaic device according to the present embodiment, which has a diffusion layer structure similar to the selective emitter structure, is manufactured.

  For comparison, a manufacturing method of a selective emitter type photovoltaic device using a resist pattern is shown in FIGS. In addition, the same code | symbol is attached | subjected about the same member as FIGS. 1-1 to FIGS. 1-9. First, in the eleventh step, the first diffusion layer 2a, which is a high-concentration diffusion layer (low-resistance region), is formed by diffusing impurities on the surface on one side of the substrate 1 (FIG. 2-1).

  In the twelfth step, a protective film 3a is deposited on the surface of the first diffusion layer 2a, and a resist pattern 11 is formed on the light receiving surface side electrode formation region thereon (FIG. 2-2).

  In the thirteenth step, the protective film 3a formed on the light-receiving surface side (first diffusion layer 2a side) of the substrate 1 is subjected to blast processing using the resist pattern 11 as a mask to form an opening 3b in the protective film 3a. (Fig. 2-3). Here, the opening 3b is not formed in the portion of the protective film 3a covered with the resist pattern 11, but the opening 3b is not formed.

  In the fourteenth step, after removing the resist pattern 11, one surface of the light-receiving surface side (first diffusion layer 2a side) of the substrate 1 using the protective film 3a having the opening 3b and the opening-unformed portion 3c as a mask In contrast, wet etching using an alkaline aqueous solution is performed as anisotropic etching to roughen the light-receiving surface side (first diffusion layer 2a side) of the substrate 1 (FIG. 2-4). By this etching, the first diffusion layer 2a is removed except in a region below the opening non-forming portion 3c. A first impurity diffusion layer 2c (hereinafter, referred to as a first diffusion layer 2c) having a flat surface serving as a formation region of the light receiving surface side electrode is formed in a lower region of the opening unformed portion 3c on the surface of the substrate 1. ) Remains. In addition, a rough surface shape 4 having a concavo-convex shape called a random pyramid is formed in the other region on the surface of the substrate 1.

  In the fifteenth step, the protective film 3a and the opening-unformed portion 3c are removed by, for example, hydrofluoric acid (FIGS. 2-5).

  In the sixteenth step, the second diffusion layer 5 which is a low concentration diffusion layer (high resistance region) is formed on the light receiving surface side of the substrate 1 (FIG. 2-6). Since the first diffusion layer 2c is already a high concentration diffusion layer, the second diffusion layer 5 which is a low concentration diffusion layer is formed only on the slope of the rough surface shape 4, and the first diffusion layer 2c is left as it is. It is a high concentration diffusion layer.

  In the seventeenth step, an antireflection film 6 made of a silicon nitride film is formed by, for example, plasma CVD on the light receiving surface side of the substrate 1 on which the rough surface shape 4 is formed (FIGS. 2-7).

  In the 18th step, a metal paste to be an electrode is applied to the substrate 1 by screen printing (FIGS. 2-8). On the front side (light-receiving surface side) of the substrate 1, for example, silver paste 7 a mixed with silver is applied in a comb shape in a grid electrode shape and a bus electrode shape with a line width of 100 μm. On the back side of the substrate 1, an aluminum paste 8a mixed with aluminum is applied to the entire surface by screen printing. In FIG. 2-8, only silver (Ag) paste 7a and aluminum paste 8a applied in a grid electrode shape are shown. Here, the silver paste 7a needs to be printed in accordance with the first diffusion layer 2c which is a high concentration diffusion layer.

  In the nineteenth step, the metal paste is fired to form the light-receiving surface side electrode 7 and the back surface electrode 8 (FIGS. 2-9). Thereafter, the shorted portion of the pn junction on the outer peripheral portion of the substrate 1 is removed by laser cutting. As described above, the selective emitter type photovoltaic device is manufactured.

  When the method for manufacturing a photovoltaic device according to the present embodiment is compared with the method for manufacturing a photovoltaic device using a resist pattern, in the method for manufacturing a photovoltaic device according to the present embodiment, the resist pattern 11 No formation is necessary. For this reason, the manufacturing method of the photovoltaic apparatus according to the present embodiment is simple to manufacture and low in manufacturing cost.

  FIG. 3-1 shows the light reception of the substrate 1 at the time when the second diffusion layer 5 is formed (sixth step, FIG. 1-6) in the method for manufacturing the photovoltaic device according to the present embodiment described above. It is a top view which shows the state of a surface side typically. 3-2 is an enlarged view showing a part of FIG. 3-1. FIG. 4 shows the light-receiving surface of the substrate 1 at the time when the second diffusion layer 5 is formed (16th step, FIGS. 2-6) in the method of manufacturing the selective emitter type photovoltaic device using the resist pattern described above. It is a top view which shows the state of the side typically.

  As shown in FIG. 3, in the method of manufacturing the photovoltaic device according to the present embodiment, the fine first diffusion layer 2a, which is a high concentration diffusion layer (low resistance region), is formed on the entire light receiving side of the substrate 1. Finely distributed. For this reason, no matter where the light receiving surface electrode is formed on the light receiving side of the substrate 1, the light receiving surface electrode is positioned on the fine first diffusion layer 2a which is a high concentration diffusion layer (low resistance region). Therefore, it is not necessary to strictly align the printing positions when printing the metal paste in the eighth step.

  On the other hand, in the method of manufacturing a selective emitter type photovoltaic device using a resist pattern as shown in FIG. 4, the first diffusion layer 2c, which is a high concentration diffusion layer (low resistance region), is a region where the light receiving surface side electrode is formed. It is made only for. For this reason, it is necessary to strictly align the printing position with the first diffusion layer 2c when printing the metal paste in the eighteenth step, and the load is large. Therefore, the method for manufacturing a photovoltaic device according to the present embodiment has a simpler process and less load than the method for manufacturing a photovoltaic device using a resist pattern.

  In the method of manufacturing a selective emitter type photovoltaic device using a resist pattern, a portion other than the electrode width (light receiving surface side electrode 7) is formed in the first diffusion layer 2c which is a high concentration diffusion layer (low resistance region). The portion that is not) becomes an electron recombination region, which is not preferable, but there is a limit to the alignment accuracy of the printing of the metal paste. Therefore, characteristic deterioration due to the first diffusion layer 2c is inevitable.

  On the other hand, in the method for manufacturing the photovoltaic device according to the present embodiment, the total area of the fine first diffusion layer 2a which is a high concentration diffusion layer (low resistance region) is a selective emitter using a resist pattern. The first diffusion layer in the region where the light receiving surface side electrode 7 is not formed on the light receiving surface side of the substrate 1 as long as it is equal to or less than the area of the first diffusion layer 2c in the manufacturing method of the photovoltaic device The characteristic degradation due to 2a can be ignored.

  In the photovoltaic device according to the present embodiment, the first diffusion layer 2a is a high-concentration diffusion layer (low resistance region), and phosphorus (P) is used in the first step and the sixth step. Is diffused twice, so that the sheet resistance is low with respect to other regions. The first diffusion layer 2a is scattered all over the light receiving side of the substrate 1, thereby reducing the connection resistance with the light receiving surface side electrode 7 formed thereon, and collecting electrons generated by light irradiation. Efficiency can be improved and photoelectric conversion efficiency can be improved.

  The first diffusion layer 2a is an electron recombination region other than the lower region of the light receiving surface side electrode. For this reason, there exists an optimum value that maximizes the photoelectric conversion efficiency as the area ratio of the area of the first diffusion layer 2a (unetched region 2b) to the area on the light receiving surface side of the substrate 1, and as a result of examination, 3% to We found 15% to be optimal. However, this value also differs depending on the size relationship (ratio) of the sheet resistance between the first diffusion layer 2a, which is a high concentration diffusion layer (low resistance region), and other regions. When the resistance ratio is small, the larger value is the optimum value.

  As described above, according to the present embodiment, the substrate 1 of the light-receiving surface side electrode 7 and the resistance of the light-receiving surface are increased by a simpler process than the method of manufacturing the selective emitter type photovoltaic device using the resist pattern. A photovoltaic device having a diffusion layer structure similar to the selective emitter structure capable of reducing the connection resistance of the light source and having a photoelectric conversion efficiency equal to or higher than that of the selective emitter structure is obtained. And according to this Embodiment, reduction of the manufacturing cost of a photovoltaic apparatus and reduction of electric power generation cost are possible.

  Next, the present invention will be described based on specific examples. The photovoltaic devices of Example 1 and Example 2 were manufactured by the method for manufacturing a photovoltaic device according to this embodiment described above. In the photovoltaic device of Example 1, the sheet resistance of the first diffusion layer 2a is 20Ω / □, and the sheet resistance of the other region (second diffusion layer 5) on the light receiving surface side of the substrate 1 is 120Ω / □. Produced. In the photovoltaic device of Example 2, the sheet resistance of the first diffusion layer 2a is 50Ω / □, and the sheet resistance of the other region (second diffusion layer 5) on the light receiving surface side of the substrate 1 is 80Ω / □. Produced.

  Here, a plurality of photovoltaic devices of Example 1 and Example 2 were produced by changing the area ratio of the area of the first diffusion layer 2a to the area on the light receiving surface side of the substrate 1, and the photoelectric conversion efficiency was increased. The optimum value of the maximum area ratio was examined. As a result, in the photovoltaic device of Example 1, the optimum area ratio was about 3% to 9%. In the photovoltaic device of Example 2, the optimum area ratio was about 10% to 15%.

  For comparison, a selective emitter type photovoltaic device of a comparative example was manufactured by the method of manufacturing a selective emitter type photovoltaic device using the resist pattern described above. In the selective emitter type photovoltaic device of the comparative example, the sheet resistance of the first diffusion layer 2c is 50Ω / □, and the sheet resistance of the other region (second diffusion layer 5) on the light receiving surface side of the substrate is 80Ω / □. As produced. In the selective emitter type photovoltaic device of the comparative example, the area ratio of the area of the first diffusion layer 2c to the area on the light receiving surface side of the substrate was set to 14%.

  Next, the photovoltaic device of Example 1 in which the area ratio is 5%, the photovoltaic device of Example 2 in which the area ratio is 12%, and the selective emitter type photovoltaic device of the comparative example are as follows. As characteristics, open circuit voltage Voc, short circuit current density Jsc, fill factor FF, and photoelectric conversion efficiency were examined. The results are shown in Table 1.

  As can be seen from Table 1, in the photovoltaic devices of Example 1 and Example 2, the open-circuit voltage Voc is lower than that of the photovoltaic device of the comparative example, but the short-circuit current density Jsc is increased to increase the comparative example. It can be seen that the photoelectric conversion efficiency is improved. Therefore, it can be said that the photovoltaic devices of Example 1 and Example 2 can obtain better photovoltaic characteristics while the manufacturing process is simpler than that of the selective emitter type photovoltaic device of the comparative example.

  In addition, a plurality of photovoltaic devices having the configuration described in the above embodiment are formed, and adjacent photovoltaic devices are electrically connected in series or in parallel, so that a solar cell with excellent photoelectric conversion efficiency is obtained. Modules can be realized at low cost. In this case, for example, one light receiving surface side electrode 7 and the other back surface electrode 8 of the adjacent photovoltaic device may be electrically connected.

  As described above, the photovoltaic device according to the present invention has a diffusion layer structure similar to the selective emitter structure, and is useful for realizing a photovoltaic device having excellent photoelectric conversion efficiency.

1 Single crystal silicon substrate (substrate)
2a First impurity diffusion layer (first diffusion layer)
2b Unetched region 2c First impurity diffusion layer (first diffusion layer)
3a Protective film 3b Opening 3c No opening forming part 4 Rough surface shape 5 Second impurity diffusion layer (second diffusion layer)
6 Antireflection film 7a Silver paste 7 Light receiving surface side electrode 8 Back surface electrode 8a Aluminum paste 11 Resist pattern

Claims (8)

A first-conductivity-type single crystal silicon substrate having a concavo-convex shape formed on one surface side;
A plurality of first diffusion layers that are dispersed and arranged on top of the convex portions of the concavo-convex shape over the entire surface on one surface side of the single crystal silicon substrate, and in which the impurity element of the second conductivity type diffuses at a first concentration;
A second diffusion formed in a region other than the first diffusion layer on one surface side of the single crystal silicon substrate, wherein the impurity element of the second conductivity type is diffused at a second concentration lower than the first concentration. Layers,
A light receiving surface side electrode electrically connected to the first diffusion layer and formed on one surface side of the single crystal silicon substrate;
A back side electrode formed on the other side of the single crystal silicon substrate;
A photovoltaic device comprising: The sheet resistance of the first diffusion layer is 20Ω / □ to 50Ω / □,
The sheet resistance of the second diffusion layer is 80Ω / □ to 120Ω / □,
The total area of the first diffusion layer is 3% to 15% with respect to the area of one surface side of the single crystal silicon substrate;
The photovoltaic device according to claim 1. A first step of diffusing a second conductivity type impurity element at a first concentration to form a first diffusion layer on the entire surface of one surface side of the first conductivity type single crystal silicon substrate;
A second step of depositing a protective film on the surface of the first diffusion layer;
A third step of subjecting the protective film to blasting to form a plurality of openings on the entire surface of the protective film;
One surface side of the single crystal silicon substrate is subjected to anisotropic etching with respect to the one surface side of the single crystal silicon substrate under the condition that the protective film is resistant with the protective film having the opening formed as an etching mask. The first diffusion layer is formed on the one surface side of the single crystal silicon substrate by forming the concavo-convex shape and leaving the first diffusion layer not subjected to the anisotropic etching in the lower region of the protective film. A fourth step of dispersively arranging the entire surface;
A fifth step of removing the protective film;
An impurity element of a second conductivity type is diffused at one surface side of the single crystal silicon substrate at a second concentration lower than the first concentration, so that other than the first diffusion layer on the one surface side of the single crystal silicon substrate. A sixth step of forming a second diffusion layer in the region;
A seventh step of forming an electrode on one side of the single crystal silicon substrate;
An eighth step of forming electrodes on the other surface side of the single crystal silicon substrate;
A method for manufacturing a photovoltaic device, comprising: In the fourth step, adjusting the etching conditions so that an unetched region not subjected to the anisotropic etching remains in the first diffusion layer in the lower region of the protective film;
The method for manufacturing a photovoltaic device according to claim 3. In the fourth step, wet etching is performed using at least one of an alkaline aqueous solution and an alkaline aqueous solution containing an additive as an etching solution;
The method for manufacturing a photovoltaic device according to claim 3 or 4, wherein: The sheet resistance of the first diffusion layer is 20Ω / □ to 50Ω / □, the sheet resistance of the second diffusion layer is 80Ω / □ to 120Ω / □, and the area of the unetched region is the single crystal silicon substrate 3% to 15% with respect to the area on the one surface side,
The method for manufacturing a photovoltaic device according to any one of claims 3 to 5, wherein: The protective film is any one of a silicon thermal oxide film, a silicon oxide film or a silicon nitride film formed by chemical deposition or physical deposition, or a combination thereof;
A method for manufacturing a photovoltaic device according to any one of claims 3 to 6. At least two or more of the photovoltaic devices according to claim 1 or 2 are electrically connected in series or in parallel;
A photovoltaic module characterized by.

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