TWI584486B - Solar cell and manufacturing method thereof - Google Patents

Description

Solar battery unit and method of manufacturing same

The present invention relates to a solar cell unit and a method of fabricating the same.

The solar cell is a semiconductor element that converts light energy into electric energy, and has a p-n junction type, a pin type, a Schottky type, etc., and in particular, a p-n junction type is most widely used. Further, when the solar cell is classified based on the substrate material, it is roughly classified into three types: a crystallization type solar cell, an amorphous 矽-type solar cell, and a compound semiconductor-type solar cell.矽 Crystalline solar cells are further classified into single crystal solar cells and polycrystalline solar cells. Since a ruthenium crystal substrate for a solar cell is relatively easy to manufacture, a ruthenium crystal solar cell is most popular.

The demand for solar cells as green energy has increased in recent years, and the demand for solar cells has increased. Further, from the viewpoint of energy efficiency, it is desirable to increase the conversion efficiency (hereinafter also referred to as conversion efficiency) of the solar cell unit from light energy to electric energy as much as possible. Further, in order to efficiently convert electric energy, it is desirable to increase the size of the solar cell, and when the solar cell is enlarged, the solar cell must be enlarged.

Non-patent documents 1 and 2 disclose a solar cell using a 1 cm angle of a p-type 矽 single crystal substrate having a conversion efficiency of 21.3% of the surface and 19.8% of the back surface, and further discloses a conversion efficiency of 16.3% for the surface and 15.0% for the back surface. A solar cell of 125 mm angle of a p-type 矽 single crystal substrate.

[prior technical literature] [Non-patent literature]

[Non-Patent Document 1] "Applied Neostructured Thin Film Solar Cell" commissioned by PVTEC (Solar Power Generation Technology Research and Development) by Hitachi, Ltd., Shinsei Manufacturing Co., Ltd., April 28, 2008, by Hitachi, Ltd., NEWS RIRSU NEDO (New Energy Industry Technology Development Organization) Manufacturing Technology Development

[Non-Patent Document 2] Japanese Society of Mechanical Engineering NEWS LETTER POWER & ENERGYSYSTEM No. 35 November 2007

However, in the solar battery cell described in Non-Patent Document 1, the conversion efficiency is 21.3% on the surface and 19.8% on the back surface. Therefore, the size of the solar battery cell can be reduced to a size of, for example, a small size of about 1 cm × 1 cm. For example, a solar cell having a size of about 12.5 cm × 12.5 cm has a conversion efficiency of only 16.3% on the surface and 15.0% on the back surface. (Refer to the above-mentioned non-patent document 1)

Therefore, in view of the above circumstances, it is an object of the present invention to provide a large-sized solar cell unit capable of achieving sufficient conversion efficiency and a method of manufacturing the same.

In order to achieve the foregoing objective, a solar cell unit is provided according to the present invention, which is directed to: n-type germanium single crystal substrate; formed in the former single crystal a p-type diffusion layer on one side of the substrate; an n-type diffusion layer formed on the other surface of the pre-recorded single crystal substrate; and one or a plurality of light-receiving surface gate electrodes and bus bars partially formed in the pre-p-type diffusion layer An electrode; and a solar cell partially formed of one or a plurality of light-receiving surface gate electrodes and a bus bar electrode of the n-type diffusion layer, wherein the p-type diffusion layer is formed with a plurality of high-concentration p-types In the field of diffusion; and in the field of low-concentration p-type diffusion between the high-concentration p-type diffusion fields, the n-type diffusion layer is formed with a plurality of high-concentration n-type diffusion fields; and in the high-concentration n-type diffusion field In the low-concentration n-type diffusion field, the light-receiving gate electrode and the bus bar electrode are adjacently formed in the high-concentration p-type diffusion field and the high-concentration n-type diffusion field, and the surface power generation capacity is 18% or more. The conversion efficiency of the other surface of the n-type diffusion layer is 93% or more of the conversion efficiency of the surface on which one of the p-type diffusion layers is formed.

According to the present invention, there is provided a solar cell unit comprising: an n-type germanium single crystal substrate; a p-type diffusion layer formed on a surface of one of the front single crystal substrates; and a surface formed on the other side of the front single crystal substrate a substantially uniform n-type diffusion layer; one or a plurality of light-receiving surface gate electrodes and bus bar electrodes partially formed in the pre-p-type diffusion layer; and one or a plurality of light-receiving surface gate electrodes partially formed in the n-type diffusion layer And a solar cell comprising a bus bar electrode, characterized in that: the p-type diffusion layer is formed with: a plurality of high-concentration p-type diffusion fields; and a low-concentration p-type diffusion field between the high-concentration p-type diffusion fields The light-receiving gate electrode and the bus bar electrode are adjacently formed in the high-density p-type diffusion field, and the surface power generation capability is a conversion efficiency of 18% or more, and an n-type diffusion layer is formed. The conversion efficiency of the other surface is 93% or more of the conversion efficiency of the surface on which one of the p-type diffusion layers is formed.

Moreover, in the above solar cell, the specific resistance of the pre-recorded single crystal substrate may also be 1 to 14 Ω. Cm. The high-concentration p-type diffusion field and the pre-recorded low-concentration p-type diffusion field are formed by boron diffusion. The sheet resistance of the high-concentration p-type diffusion field is 20~100Ω/□, and the sheet resistance of the low-concentration p-type diffusion field is noted. It is 30~150Ω/□. The high-density n-type diffusion field and the pre-recorded low-concentration n-type diffusion field are formed by phosphorus diffusion. The sheet resistance of the high-concentration n-type diffusion field is 20~100Ω/□, and the sheet resistance of the low-concentration n-type diffusion field is noted. It is 30~150Ω/□. Further, the n-type diffusion layer which is comprehensive and uniform in the foregoing is formed by diffusion of phosphorus, and the sheet resistance is 30 to 150 Ω/□.

Further, the p-type diffusion layer and the n-type diffusion layer may be covered with a protective insulating film, and the p-type diffusion layer and the n-type diffusion layer may be covered with an anti-reflection film, and the p-type diffusion layer and the pre-type n-type are described above. An insulating film for protection may be provided between the diffusion layer and the antireflection film.

Further, the front-receiving light-receiving gate electrode and the front-side bus bar electrode may be formed by overlapping two layers to form the first electrode layer and the second electrode layer. Here, the first electrode layer has a lower contact resistance with the tantalum single crystal substrate than the second electrode layer, and is preferably stronger than the tantalum single crystal substrate, and the second electrode layer and the first electrode are described above. Compared to the layer, the volume specific resistance value can also be low. Further, the light-receiving gate electrode and the front busbar electrode may be formed by screen printing. Further, the light-receiving gate electrode and the front bus bar electrode may be formed of only one layer of the first electrode layer.

Moreover, the present invention provides a method of manufacturing a solar battery cell according to another aspect of the invention, comprising: forming a plurality of high-concentration p-type diffusion fields on one side of an n-type single crystal substrate; a process for forming a p-type diffusion layer in a low-concentration p-type diffusion region between the high-concentration p-type diffusion domains; forming a plurality of high-concentration n-type diffusions on the other side of the n-type germanium single crystal substrate a process for forming an n-type diffusion layer in the field of low-concentration n-type diffusion between the high-concentration n-type diffusion domains; and forming a light-receiving surface adjacent to the high-concentration p-type diffusion field and the high-concentration n-type diffusion field The process of the gate electrode and the bus bar electrode.

Further, according to the present invention, there is provided a method of manufacturing a solar battery cell comprising: forming a plurality of high-concentration p-type diffusion regions on a surface of one of n-type germanium single crystal substrates; and providing the high concentration p a process for forming a p-type diffusion layer in the field of low-concentration p-type diffusion between the types of diffusion; forming a completely uniform n-type diffusion layer on the other side of the n-type single crystal substrate; and forming an abutment The process of the high-concentration p-type diffusion field and the light-receiving surface gate electrode and the bus bar electrode of the fully uniform n-type diffusion layer are described.

In the above manufacturing method of the solar cell, the specific resistance of the pre-recorded single crystal substrate may also be 1 to 14 Ω. Cm. Further, the p-type diffusion layer and the n-type diffusion layer may be coated or attached in advance to a liquid or a solid containing a boron element corresponding to the p-type diffusion layer and a liquid or solid containing a phosphorus element corresponding to the n-type diffusion layer. A single crystal substrate is formed simultaneously with heat treatment.

Further, the pre-recorded p-type diffusion layer and the n-type diffusion layer may also contain corresponding a liquid or a solid of boron element of the p-type diffusion layer, coated or adhered to a single crystal substrate, heat-treated, and secondly, a liquid or solid containing a phosphorus element corresponding to the n-type diffusion layer is coated or attached to the single crystal The substrate is then subjected to heat treatment to form a pre-p-type diffusion layer and an n-type diffusion layer, respectively.

Moreover, in order to simultaneously form a high-concentration p-type diffusion field or a high-concentration n-type diffusion field, a liquid or solid containing boron element may be changed or coated or adhered to a high-concentration p-type diffusion field and a low-concentration p-type diffusion field, respectively. Amount, or coating a different liquid (or solid) such as the amount of boron, or changing the liquid or solid containing phosphorus, respectively, coated or attached to the high-concentration n-type diffusion field and the low-concentration n-type diffusion field. The amount, or the application of different liquids (or solids) such as the amount of phosphorus, is simultaneously heat-treated to form a high-concentration p-type diffusion field and a low-concentration p-type diffusion field, a high-concentration n-type diffusion field, and a low-concentration n-type diffusion field.

In addition, in order to simultaneously form the high-density p-type diffusion field and the high-concentration n-type diffusion field, it is also possible to form a mask using screen printing on both sides in the field of forming a low-concentration p-type diffusion field and a low-concentration n-type diffusion field. Process. On the other hand, in order to simultaneously form the low-density p-type diffusion field and the low-concentration n-type diffusion field, it is also possible to form a mask using screen printing on both sides in the field of forming a high-concentration p-type diffusion field and a high-concentration n-type diffusion field. Process.

Further, the formation of the p-type diffusion layer by boron diffusion and the formation of the pre-type n-type diffusion layer by phosphorus diffusion are performed separately, and in the case of boron diffusion, the surface of the p-type diffusion layer on which the pre-recorded single crystal substrate is formed is performed. The mask process using screen printing is used to form a pre-recorded single crystal substrate during phosphorus diffusion. The surface of the n-type diffusion layer may be subjected to a mask process using screen printing.

Further, a method of forming a high-concentration p-type diffusion field or a high-concentration n-type diffusion field at the same time, or simultaneously baking a conductive paste having a self doping effect, thereby forming a diffusion field. Alternatively, each of the methods of forming a high-concentration p-type diffusion field or a high-concentration n-type diffusion field may be separately fired into a conductive paste having a self-doping effect, thereby forming a diffusion field.

Further, a method of forming a high-concentration p-type diffusion field or a high-concentration n-type diffusion field may be separately formed, and a diffusion layer may be formed by a laser doping method.

Further, the masking agent used in the pre-mask process can also have fluorine acid resistance and nitric acid resistance, and can be peeled off by an aqueous alkaline solution. The method of forming the masking agent can also utilize a screen printing method.

Further, in the process of forming the n-type diffusion layer, a film which can be removed by using a hydrofluoric acid aqueous solution formed on the surface of the p-type diffusion layer may be used as a masking agent. Here, the masking agent used is a borosilicate glass film or a phosphoric acid glass film, a thermal oxide film or a borophosphonate glass film, a titanium oxide film or a tantalum nitride film which can be removed by using a hydrofluoric acid aqueous solution. It is better. The method of forming the masking agent may be any one of heat treatment, thermal CVD treatment, and plasma CVD.

Further, in the process of forming the front surface of the light-receiving gate electrode and the front busbar electrode, the first light-receiving gate electrode and the front busbar electrode may be stacked in two layers to form the first electrode layer and the second electrode layer. The first electrode layer has a lower contact resistance with the tantalum single crystal substrate than the second electrode layer, and has a strong bonding strength with the tantalum single crystal substrate, and the second electrode layer is preceded by the first electrode layer. The ratio can be lower for a specific resistance value. Also, the front light receiving gate The electrode and the front bus bar electrode can also be formed by screen printing.

Further, the light-receiving gate electrode and the front bus bar electrode may be formed of only one layer of the first electrode layer.

The present invention provides a large-sized solar cell unit and a method of manufacturing the same that can achieve sufficient conversion efficiency.

Embodiments of the present invention will be described below with reference to the drawings. In the present specification and the drawings, constituent elements that have substantially the same functional configuration are denoted by the same reference numerals, and the description thereof will not be repeated.

(a) to (m) are explanatory views of a process for manufacturing the solar battery cell A using the semiconductor substrate W (hereinafter also simply referred to as the substrate W) of the n-type single crystal substrate. First, as shown in Fig. 1(a), for example, a crystal orientation (100), a 15.6 cm angle, a thickness of 100 to 300 μm, and a resistance ratio of 1 to 1 produced by the CZ method (Czochralski method) are prepared. 14.0Ω. An n-type semiconductor substrate W of a cm single crystal substrate.

Next, the semiconductor substrate W is immersed in a high concentration (for example, 10% by weight) aqueous sodium hydroxide solution to remove the damaged layer. Further, the substrate W is immersed in a low concentration (for example, 2 wt%) aqueous sodium hydroxide solution to form a texture structure on the entire surface of the substrate W. Then, the substrate W is washed.

The reason for forming the texture structure above is because solar cells are generally It is preferable that the surface has an uneven shape, and in order to reduce the reflectance of the visible light region by the formation of the texture structure, it is necessary to perform the reflection twice or more by the light receiving surface. Therefore, the semiconductor substrate W after the damage layer is removed is immersed in, for example, an aqueous solution of isopropyl alcohol in a 2 wt% aqueous sodium hydroxide solution, and wet etching is performed to form a texture structure on the surface of the semiconductor substrate W. Here, the size of the mountain of the texture structure is about 0.3 to 20 μm. Other representative surface uneven structures include V-shaped grooves and U-shaped grooves, and these shapes can be formed using a grinder. Further, in order to form an arbitrary concavo-convex structure, in addition to the above methods, for example, acid etching, ion reaction etching, or the like can be used.

Next, as shown in FIG. 1(b), an oxide film 5 is formed on both the front surface and the back surface of the substrate W by heat treatment at 980 ° C in an atmosphere containing oxygen. Further, a nitride film may be formed instead of the oxide film 5.

Next, as shown in Fig. 1(c), on the surface 10 of the oxide film 5, the photoresist film 7 is coated with a thickness of, for example, 10 to 30 μm in a predetermined pattern. Then, as shown in Fig. 1(d), the photoresist film 7 is used as a mask, and wet etching using, for example, a 10% HF aqueous solution is performed, and the oxide film 5 of the surface 10 is etched into a predetermined pattern. At this time, the oxide film 5 is etched to form a predetermined pattern of the photoresist film 7.

Next, as shown in Fig. 1(e), the resist film 7 on both the front and back surfaces is removed by peeling off with an aqueous alkaline solution.

Next, in a diffusion furnace set at 1000 ° C, as shown in Fig. 1 (f), an oxide film 5 etched into a predetermined pattern is used as a mask in an atmosphere containing boron tribromide (BBr ₃ ) gas. Boron diffusion is applied to the exposed portion of the surface 10 of the substrate W. Accordingly, a plurality of high-concentration p-type diffusion regions 15 are formed in stripes on the surface 10 of the substrate W. Further, the sheet resistance of the high-concentration p-type diffusion region 15 is preferably 20 to 60 Ω/□ (ohm/square). Further, although the method of diffusing boron is exemplified by a coating diffusion method under ambient gas of boron tribromide (BBr ₃ ) gas, it is not limited thereto, and for example, boron trichloride (BCl ₃ ) gas or The boron oxide (B ₂ O ₅ ) gas can also be diffused by spraying. Further, boron diffusion may be performed by using BN (boron nitride) as a source, or by screen printing, inkjet, spraying, spin coating or the like.

Next, as shown in Fig. 1(g), the oxide film 5 of the surface 10 is removed by wet etching using, for example, a 10% aqueous HF solution. Further, in the diffusion furnace set at 930 ° C, boron diffusion was performed on the entire surface 10 of the substrate W under an atmosphere containing a boron tribromide (BBr ₃ ) gas. Accordingly, in the surface 10 of the substrate W, as shown in FIG. 1(h), a low-concentration p-type diffusion region 16 is formed between the plurality of high-concentration p-type diffusion regions 15. Even here, a borosilicate glass film (not shown) may be formed on both the front and back surfaces of the substrate W. Further, the sheet resistance of the low-concentration p-type diffusion region 16 is preferably 30 to 150 Ω/□ (ohm/square).

Next, the masking agent was printed on the surface 10 by screen printing, and dried in a hot air drying oven at 180 °C. The borosilicate glass film (not shown) formed on the surface 10 of the substrate W is protected by the printing of the masking agent. The masking agent is preferably a material which has fluorine-resistant acidity and nitric acid resistance and can be peeled off by an aqueous alkaline solution.

Next, the substrate W in a state where the masking agent is printed on the surface 10 (after drying) is immersed in, for example, a fluorine-nitrogen nitrate aqueous solution or a hydrofluoric acid aqueous solution, and the other surface of the substrate W using the unprinted masking agent is removed (hereinafter referred to as The high concentration p-type diffusion field formed by the borosilicate glass film (not shown) or out-diffusion of the back surface 20). Then, the masking agent 18 is removed by using, for example, an aqueous solution of sodium hydroxide, and the substrate W is washed and dried.

Next, in an electric diffusion furnace set at 870 ° C, an oxide film 5 of a predetermined pattern formed by the same method as in the case of the surface 10 described above is etched under an atmosphere containing phosphorus oxychloride (POCl ₃ ) gas. For the mask, phosphorus diffusion is performed on the exposed portion of the back surface 20 of the substrate W. Further, even in the phosphorus diffusion of the back surface 20, the boron film is diffused in the same manner as the boron diffusion on the surface 10, and the oxide film 5 and the photoresist film 7 are patterned to form a diffusion region, but the oxide film 5 and the photoresist are related. The formation of the film 7 or the removal of the oxide film 5 and the photoresist film 7 after the phosphorus diffusion is the same as the case described in the above-described first drawings (b) to (f), and the description thereof will be omitted.

Accordingly, as shown in FIG. 1(i), a plurality of high-concentration n-type diffusion regions 25 are formed in stripes on the back surface 20 of the substrate W. Further, the sheet resistance of the high-concentration n-type diffusion region 25 is preferably 20 to 60 Ω/□ (ohm/square). Further, phosphorus diffusion is performed by an inkjet method, a spray, a spin coating, a laser doping method, or the like.

Further, in an electric diffusion furnace set at 830 ° C, phosphorus diffusion was performed on the entire back surface 20 of the substrate W under an atmosphere containing phosphorus oxychloride (POCl ₃ ) gas. Accordingly, as shown in FIG. 1(j), in the back surface 20 of the substrate W, a low-concentration n-type diffusion region 26 is formed between the plurality of high-concentration n-type diffusion regions 25. At this time, a phosphoric acid glass film (not shown) is formed on both the front surface and the back surface of the substrate W. Further, the sheet resistance of the low-concentration p-type diffusion field 26 is preferably 30 to 150 Ω/□ (ohm/square).

Next, the PN junction separation of the peripheral portion of the substrate W is performed by a plasma etcher, and in the above-described process, boron bismuth formed on the surface 10 and the back surface 20 of the substrate W is removed by etching using a hydrofluoric acid aqueous solution. A phosphate glass film (not shown) and a phosphoric acid glass film (not shown). Then, an anti-reflection film 35 such as a nitride film (SiNx film) is formed on the entire surface 10 and the back surface 20 by a plasma chemical vapor deposition (plasma CVD) apparatus. Here, other types of the anti-reflection film 35 include, for example, a titanium dioxide film, a zinc oxide film, a hafnium oxide film, and the like, and may be substituted. Further, the formation of the anti-reflection film 35 is performed by a direct plasma CVD method using a plasma CVD apparatus, but it is also possible to use, for example, a remote plasma CVD method or a vacuum evaporation method. Wait. However, from the economic point of view, it is most suitable to form a nitride film by a plasma CVD method. Further, in order to minimize the total reflectance on the anti-reflection film 35, for example, a film having a refractive index of between 1 and 2 of the magnesium fluoride film is formed to promote a decrease in reflectance and increase a current density. Further, a protective insulating film may be formed between the substrate W and the anti-reflection film 35.

Next, as shown in Fig. 1 (1), a first electrode layer 40 made of, for example, a conductive paste containing silver (Ag) is printed on the back surface 20 of the substrate W in a predetermined pattern by using a screen printing machine. High concentration n-type diffusion field 25 surface (lower in the figure), then dry. Further, for example, the second electrode layer 42 made of a silver-containing conductive paste is printed on the surface (lower side in the figure) of the first electrode layer 40 formed on the high-concentration n-type diffusion region 25 by screen printing. And dry. The first electrode layer 40 and the second electrode layer 42 are laminated to form a light-receiving surface gate electrode and a bus bar electrode (hereinafter collectively referred to as an electrode 45). Further, the first electrode layer 40 printed on the surface of the high-concentration n-type diffusion region 25 may be formed of a conductive paste having a self-doping effect in the calcination process, which may include a phosphorus element. Further, in the present embodiment, the electrode 45 is constituted by the first electrode layer 40 and the second electrode layer, but the electrode 45 may be formed of a single-layer conductive paste.

Next, as shown in Fig. 1(m), as in the case shown in Fig. 1 (1) above, for example, the first electrode layer 40 made of a conductive paste containing silver (Ag) is predetermined. The pattern was printed on the surface of the high concentration p-type diffusion field 15 (above in the figure) and then dried. Further, for example, the second electrode layer 42 made of a conductive paste containing silver (Ag) is printed on the surface of the first electrode layer 40 formed on the high-concentration p-type diffusion region 15 by screen printing (in the figure) Above), dry. Further, the first electrode layer 40 printed on the surface of the high-concentration p-type diffusion region 15 may be formed of a conductive paste having a boron element and having a self-doping effect in the firing process. Further, in the present embodiment, the electrode 45 is constituted by the first electrode layer 40 and the second electrode layer, but the electrode 45 may be formed of a single-layer conductive paste.

Here, the first electrode layer 40 has a lower contact resistance with the tantalum single crystal substrate (semiconductor substrate W) than the second electrode layer 42 and It is preferable that a material having a strong bonding strength of a single crystal substrate (semiconductor substrate W) is formed. Further, the second electrode layer 42 has a lower volume specific resistance value than the first electrode layer 40, and is excellent in conductivity. The electrode 45 has an object of efficiently extracting electrons generated in the substrate W. Therefore, it is desirable to increase the height of the electrode 45, or to reduce the contact resistance of the interface where the electrode 45 is in contact with the substrate W, the volume specific resistance of the electrode 45 is low, and the like. In these problems, the structure of the electrode 45 is a two-layer structure made of the first electrode layer 40 and the second electrode layer 42, and the height of the electrode 45 is increased, and the first electrode layer 40 is disposed at a position in contact with the substrate W. In this case, the contact resistance with the substrate W is lowered, and since the second electrode layer 42 is not in contact with the substrate W, the volume specific resistance value is lower than that of the first electrode layer 40.

Further, the application electrode 45 is formed in the high-concentration p-type diffusion region of the surface 10 and the substrate W in the high-concentration n-type diffusion region of the back surface 20 to form the solar battery cell A.

Fig. 2 is a schematic explanatory view of the solar battery unit A viewed obliquely from above. In addition, Fig. 2 is an enlarged view showing a part of the solar battery cell A, and a schematic cross section of the solar battery cell A is also shown. As shown in Fig. 2, a high-concentration p-type diffusion region is disposed on the surface 10 of the semiconductor substrate W, and electrodes made of two layers (the first electrode layer 40 and the second electrode layer 42) are formed on the front surface thereof. 45, and a high-concentration n-type diffusion field is disposed on the back surface 20, and an electrode 45 made of two layers is formed directly under the above-described process, and the in-plane uniformity of the sheet resistance is sufficiently ensured, and the surface and the back surface of the solar battery cell A are provided. Each of the power generation capabilities has a conversion efficiency of 18% or more of solar cells.

Further, a solar battery cell A having a larger ratio of a conversion efficiency (Bifaciality) to the back surface of the surface of the solar cell A is 93% or more, for example, a size of 15.6 cm.

In addition, the fabrication electrode 45 has a structure in which the first electrode layer 40 and the second electrode layer 42 are laminated, and the solar battery cells A of the electrons generated in the substrate W can be efficiently taken out.

Although an example of the embodiment of the present invention has been described above, the present invention is not limited to the illustrated embodiment. For those skilled in the art, it is to be understood that various changes and modifications may be made without departing from the scope of the invention.

In the above-described embodiment, the formation of the low-concentration diffusion region (p-type, n-type) is performed after forming the high-concentration diffusion region (both p-type and n-type), but the diffusion layer formation method is not necessarily limited. This method. For example, a method of forming a high-concentration diffusion region (p-type, n-type) and a low-concentration diffusion region (p-type, n-type) on the light-receiving surface of the semiconductor substrate W may form a low concentration on the light-receiving surface of the semiconductor substrate W. After the diffusion field, a portion of the phosphoric acid glass film (or borosilicate glass film) which is required to be in the high-concentration diffusion field is subjected to additional heat treatment to form a high-concentration diffusion field.

Further, in the method of boron diffusion and phosphorus diffusion, it is also conceivable to apply a liquid or a solid containing various elements to the surface (surface, back surface) of the substrate W in advance, and then perform heat treatment to simultaneously form a high-concentration p-type diffusion field and high. A method of concentration in the field of n-type diffusion. Therefore, the case where boron diffusion and phosphorus diffusion of the substrate W are simultaneously performed will be described below with reference to FIG. again The process other than the process of applying boron diffusion and phosphorus diffusion is the same as the above-described process in the first drawing. Therefore, only the process of performing boron diffusion and phosphorus diffusion is described in FIG.

As shown in Fig. 3 (a) and (b), a liquid or a solid containing a boron element is applied or adhered to the surface 10 of the substrate W, and then dried, and a phosphorus-containing element is applied or adhered to the back surface 20 of the substrate W. After the liquid or solid is dried and dried, for example, by heat treatment in a furnace set at 900 ° C, a high-concentration p-type diffusion field 15 is formed on the entire surface 10, and a high-concentration n-type diffusion field is formed on the back surface 20 in an all-round manner. 25.

Next, as shown in Fig. 3(c), in the surface 10 on which the high-concentration p-type diffusion region 15 is formed, the photoresist film 7 is coated with a thickness of, for example, 10 to 30 μm in a predetermined pattern, and dried at 180 ° C by hot air. The furnace is dried. Next, in the high-concentration n-type diffusion region 25, the photoresist film 7 is applied with a thickness of, for example, 10 to 30 μm in a predetermined pattern, and then dried in a hot air drying oven at 180 °C. It is preferred to use a material which is resistant to fluorine acid and nitrate, and which can be peeled off by an aqueous alkaline solution.

Next, the substrate W in a state where the photoresist film 7 is printed on the front surface 10 and the back surface 20 is immersed in, for example, a fluorine-nitrogen nitrate aqueous solution, and the high-concentration p-type diffusion region 15 and the surface of the substrate W on which the photoresist film 7 is not printed are etched. The concentration n-type diffusion field 25, as shown in Fig. 3(d), forms a low concentration p-type diffusion field 16 and a low concentration n-type diffusion field 26.

Next, the photoresist film 7 is removed from both the front and back surfaces by stripping with an alkaline aqueous solution, and as shown in FIG. 3(e), a high-concentration p-type diffusion field and a high-concentration n-type are simultaneously formed. Diffusion field.

Further, in the above-described embodiment, the case where the high-concentration diffusion region is formed on both the front surface 10 and the back surface 20 of the substrate W will be described, but the present invention is not limited thereto. It is also conceivable to form, for example, a uniformly uniform n-type diffusion layer in the back surface 20 of the substrate W, and to form a high-concentration diffusion field and a low-concentration diffusion field only on the surface 10 of the substrate W.

Fig. 4 is an explanatory view of the solar battery cell A in a case where a uniform and uniform n-type diffusion layer 26' is formed on the back surface 20 of the substrate W. Further, the solar battery cell A shown in Fig. 4 has the same configuration as that of the above-described embodiment except for the configuration of the n-type diffusion layer 26' of the back surface 20.

As shown in FIG. 4, a uniform and uniform n-type diffusion layer 26 is formed on the back surface 20, and the photoresist printing process and the photoresist removal process are reduced, whereby a larger cost reduction can be achieved. Further, it is also possible to reduce thermal damage to the substrate W by reducing the heat treatment process.

[Examples] (Example 1)

In Example 1, a crystal orientation (100), an angle of 15.6 cm, a thickness of 200 μm, and a resistance ratio of 2.8 Ω prepared by the CZ method were prepared. The n-type semiconductor substrate of the cm single crystal substrate was immersed in a 10 wt% aqueous sodium hydroxide solution to remove the damaged layer. Further, the substrate was immersed in a 2 wt% aqueous sodium hydroxide solution to form a texture structure on the entire surface of the substrate. The substrate is then washed.

Next, dry oxidation at 1000 ° C was carried out to form an oxide film on the light-receiving surface. Then, a portion of the low-concentration p-type diffusion region was formed as a mask, and the photoresist was printed by a screen printing machine to be dried in a hot air drying oven at 180 °C. After drying, it was immersed in a 10 wt% aqueous solution of hydrofluoric acid to remove the oxide film of the high-concentration p-type diffusion portion, and then the photoresist was removed by a 2 wt% aqueous sodium hydroxide solution to wash and dry the substrate. Then, the substrate is diffused by BBr ₃ gas to diffuse boron to form a high-concentration p-type diffusion field.

Next, the substrate was immersed in a 10 wt% aqueous solution of hydrofluoric acid to remove the oxide film of the low-concentration p-type diffusion portion, and after drying, the substrate was again diffused in a 930 ° C electric diffusion furnace using BBr ₃ gas to carry out boron. Diffusion forms a low concentration p-type diffusion field.

Next, in the formation of a high-concentration p-type diffusion field and a low-concentration p-type diffusion field, a photoresist is printed by a screen printing machine and dried in a hot air drying oven at 180 °C. After drying, it is immersed in a fluoro-nitric acid aqueous solution to remove a borosilicate glass film or a p-type diffusion field which forms a high-concentration n-type diffusion field and a low-concentration n-type diffusion field. Then, the photoresist was removed using an aqueous solution of sodium hydroxide, and the substrate was washed and dried.

Next, dry oxidation at 1000 ° C was carried out to form an oxide film on the light-receiving surface. Then, a portion of the low-concentration n-type diffusion field was formed as a mask, and the photoresist was printed by a screen printing machine to be dried in a hot air drying oven at 180 °C. After drying, it was immersed in a 10 wt% aqueous solution of hydrofluoric acid to remove the oxide film of the high-concentration n-type diffusion portion, and then the photoresist was removed by a 2 wt% aqueous sodium hydroxide solution, and the substrate was washed and dried. Then, the substrate is diffused in an electric diffusion furnace containing an atmosphere of phosphorus oxychloride to form a high-concentration n-type diffusion field.

Next, the substrate was immersed in a 10 wt% aqueous solution of hydrofluoric acid to remove the oxide film of the low-concentration n-type diffusion portion, and after drying, the substrate was again placed in an electric diffusion furnace at 830 ° C in an atmosphere containing phosphorus oxychloride. Diffusion is carried out to form a low concentration n-type diffusion field.

Next, the PN junction separation of the peripheral portion of the substrate is performed by plasma etching, and then the phosphoric acid glass film or the borosilicate glass film formed on the surface of the substrate or the borophosphonate glass film is removed by using a hydrofluoric acid aqueous solution to form a protection. An anti-reflection film is formed by depositing a nitride film on both surfaces of the substrate by a plasma CVD apparatus using an insulating film.

Next, a gate silver (Ag) electrode and a bus bar electrode were printed on a high-concentration n-type diffusion field on the back side using a screen printing machine, and dried. Above the gate silver (Ag) electrode and the bus bar electrode, the same electrode pattern is printed and dried to form a 2-layer electrode. Further, a gate silver (Ag) electrode and a bus bar electrode were printed on a surface of a high-concentration p-type diffusion field using a screen printing machine, and dried. Above the gate silver (Ag) electrode and the bus bar electrode, the same electrode pattern is printed and dried to form a 2-layer electrode. Then, firing is performed to form a gate electrode and a bus bar electrode, thereby producing a solar cell. Tables 1 and 5 show the results of the IV characteristics of the surface and the back surface of the solar cell.

Further, Fig. 6 is a view showing an angular base at 15.6 cm after boron diffusion is performed. An explanatory diagram of the measurement result of the in-plane distribution of the sheet resistance of the sheet. For the problem of increasing the size of the substrate, for example, it is difficult to homogenize the in-plane of boron diffusion. It is understood that in the present invention, the in-plane uniformity of boron diffusion is improved to solve the problem.

Further, the change in the conversion efficiency (Eff) when the resistance ratio of the substrate was changed was shown in Fig. 7 . The change in the ratio of the back surface conversion ratio (described as Bifaciality in the graph) to the surface conversion efficiency when the resistance ratio of the substrate was changed was shown in Fig. 8 .

As shown in Figure 7 and Figure 8, the resistance ratio is known to be 1~14Ω. The range of cm can maintain the surface conversion efficiency of 18% or more and Bifaciality of 93% or more.

[Industrial Availability]

The present invention is applicable to a solar cell unit and a method of manufacturing the same.

5‧‧‧Oxide film

7‧‧‧Photoresist film

10‧‧‧ surface

15‧‧‧High concentration p-type diffusion field

16‧‧‧Low concentration p-type diffusion field

20‧‧‧ inside

25‧‧‧High concentration n-type diffusion field

26‧‧‧Low concentration n-type diffusion field

26’‧‧‧Comprehensive uniform n-type diffusion layer

30‧‧‧Oxide film

35‧‧‧Anti-reflection film

40‧‧‧1st electrode layer

42‧‧‧2nd electrode layer

45‧‧‧Electrode

A‧‧‧Solar battery unit

W‧‧‧Semiconductor substrate

Fig. 1 is an explanatory view of a process for manufacturing a solar battery cell.

Fig. 2 is a schematic explanatory view of the solar battery cell viewed obliquely from above.

Fig. 3 is an explanatory view for the case where boron diffusion and phosphorus diffusion on the substrate W are simultaneously performed.

Fig. 4 is a schematic explanatory view showing a solar battery cell in a case where a substantially uniform n-type diffusion layer is formed on the back surface as viewed obliquely from above.

Fig. 5 is a graph showing the results of the IV characteristics of the surface and the back surface of the solar cell.

Fig. 6 is an explanatory view showing the measurement result of the in-plane distribution of the sheet resistance.

Fig. 7 is a graph showing the relationship between the conversion efficiency of the surface and the back surface and the specific resistance of the substrate.

Fig. 8 is a graph showing the relationship between the ratio of the back surface conversion efficiency (Bifaciality) and the substrate resistance ratio.

W‧‧‧Semiconductor substrate

5‧‧‧Oxide film

7‧‧‧Photoresist film

10‧‧‧ surface

15‧‧‧High concentration p-type diffusion field

16‧‧‧Low concentration p-type diffusion field

20‧‧‧ inside

25‧‧‧High concentration n-type diffusion field

26‧‧‧Low concentration n-type diffusion field

30‧‧‧Oxide film

35‧‧‧Anti-reflection film

40‧‧‧1st electrode layer

42‧‧‧2nd electrode layer

45‧‧‧Electrode

Claims (19)

A solar cell unit comprising: an n-type germanium single crystal substrate; a p-type diffusion layer formed on a surface of one of the front single crystal substrates; and an n-type diffusion layer formed on the other surface of the front single crystal substrate Partially forming one or a plurality of light-receiving surface gate electrodes and bus bar electrodes of the p-type diffusion layer; and partially forming a solar energy formed by one or a plurality of light-receiving surface gate electrodes and bus bar electrodes of the n-type diffusion layer The battery unit is characterized in that: the p-type diffusion layer is formed with: a plurality of high-concentration p-type diffusion fields; and a low-concentration p-type diffusion field between the high-concentration p-type diffusion fields, and the n-type diffusion layer is preceded by Formed by: a plurality of high-concentration n-type diffusion fields; and a low-concentration n-type diffusion field located between the high-concentration n-type diffusion fields, the pre-recorded light-receiving gate electrode and the bus bar electrode are adjacently formed in the high-concentration p-type In the diffusion field and the high-concentration n-type diffusion field, the surface power generation capability is a conversion efficiency of 18% or more, and the conversion efficiency of the other surface on which the n-type diffusion layer is formed is one of the p-type diffusion layers. 93% conversion efficiency of the surface; remember the previous resistance silicon single crystal substrate is 1 ~ 14Ω. Cm; the high-concentration p-type diffusion field and the pre-recorded low-concentration p-type diffusion field are formed by boron diffusion. The sheet resistance in the high-concentration p-type diffusion field is 20~100Ω/□, and the low-concentration p-type diffusion field The sheet resistance is 30~150Ω/□; the high-density n-type diffusion field and the pre-recorded low-concentration n-type diffusion field are formed by phosphorus diffusion. The sheet resistance of the high-concentration n-type diffusion field is 20~100Ω/□, and the pre-record Sheet resistance in low concentration n-type diffusion field It is 30~150Ω/□; the fully uniform n-type diffusion layer is formed by diffusion of phosphorus, and its sheet resistance is 30~150Ω/□. A solar cell unit comprising: an n-type germanium single crystal substrate; a p-type diffusion layer formed on a surface of one of the front single crystal substrates; and a uniform uniform surface formed on the other surface of the front single crystal substrate a diffusion layer partially formed on one or a plurality of light-receiving surface gate electrodes and a bus bar electrode of the p-type diffusion layer; and one or a plurality of light-receiving surface gate electrodes and bus bar electrodes partially formed in the n-type diffusion layer The solar cell unit is characterized in that: the p-type diffusion layer is formed with: a plurality of high-concentration p-type diffusion fields; and a low-concentration p-type diffusion field between the high-concentration p-type diffusion fields, and a light-receiving surface The gate electrode and the bus bar electrode are adjacently formed in the high-concentration p-type diffusion field, and the surface power generation capability is a conversion efficiency of 18% or more, and the conversion efficiency of the other surface on which the n-type diffusion layer is formed is formed with a p-type diffusion layer. The conversion efficiency of one side of the surface is more than 93%; the resistance ratio of the pre-recorded single crystal substrate is 1 to 14 Ω. Cm; the high-concentration p-type diffusion field and the pre-recorded low-concentration p-type diffusion field are formed by boron diffusion. The sheet resistance in the high-concentration p-type diffusion field is 20~100Ω/□, and the low-concentration p-type diffusion field The sheet resistance is 30~150Ω/□; the high-density n-type diffusion field and the pre-recorded low-concentration n-type diffusion field are formed by phosphorus diffusion. The sheet resistance of the high-concentration n-type diffusion field is 20~100Ω/□, and the pre-record Sheet resistance in low concentration n-type diffusion field It is 30~150Ω/□; the fully uniform n-type diffusion layer is formed by diffusion of phosphorus, and its sheet resistance is 30~150Ω/□. The solar battery cell according to the first or second aspect of the invention, wherein the p-type diffusion layer and the n-type diffusion layer are covered with a protective insulating film. The solar battery cell according to the first or second aspect of the invention, wherein the p-type diffusion layer and the n-type diffusion layer are covered with an anti-reflection film. The solar battery cell according to the first or second aspect of the invention, wherein the light-receiving surface electrode and the front bus bar electrode are formed by overlapping two layers to form a first electrode layer and a second electrode layer. The solar cell according to the fifth aspect of the invention, wherein the first electrode layer has a lower contact resistance with the tantalum single crystal substrate than the second electrode layer, and has a strong bonding strength with the tantalum single crystal substrate. . The solar battery cell according to claim 5, wherein the second electrode layer has a volume specific resistance value lower than that of the first electrode layer. The solar battery cell according to the first or second aspect of the invention, wherein the light-receiving surface electrode electrode and the front busbar electrode are formed by screen printing. A method of manufacturing a solar battery cell, comprising: forming a plurality of surfaces on one side of an n-type single crystal substrate a process of forming a p-type diffusion layer in a high-concentration p-type diffusion field and a low-concentration p-type diffusion field between the high-concentration p-type diffusion fields; forming a complex number on the other side of the n-type single crystal substrate Process of n-type diffusion layer formed by a high-concentration n-type diffusion field and a low-concentration p-type diffusion field located between the high-concentration n-type diffusion fields; and formation of adjacency in the high-concentration p-type diffusion field and high concentration n The process of the light-receiving surface gate electrode and the bus bar electrode in the diffusion field. A method of manufacturing a solar cell according to the invention, comprising: forming a plurality of high-concentration p-type diffusion regions on a surface of one of the n-type single crystal substrates; and lowering between the high-concentration p-type diffusion regions a process for forming a p-type diffusion layer in the p-type diffusion field; a process for forming a uniform and uniform n-type diffusion layer on the other side of the n-type single crystal substrate; and forming a high-concentration p-type diffusion in the vicinity The process of the field and the uniform uniform n-type diffusion layer of the light-receiving surface gate electrode and the bus bar electrode. The method for manufacturing a solar cell according to claim 9 or claim 10, wherein the electric resistance ratio of the pre-recorded single crystal substrate is 1 to 14 Ω. Cm. The method for producing a solar cell according to claim 9 or claim 10, wherein the p-type diffusion layer and the n-type diffusion layer are liquid or solid in which boron element corresponding to the p-type diffusion layer is previously added. A liquid or solid containing a phosphorus element corresponding to the n-type diffusion layer is coated or adhered to the tantalum single crystal substrate, and then formed by heat treatment. The method for producing a solar cell according to claim 9 or 10, wherein before the diffusion using boron is performed separately The formation of the p-type diffusion layer and the formation of the pre-type n-type diffusion layer by phosphorus diffusion, and the masking process of screen-printing the surface of the p-type diffusion layer on which the single-crystal substrate is formed before the boron diffusion is performed. In the case of phosphorus diffusion, a mask process for screen printing by forming a surface of an n-type diffusion layer on which a single crystal substrate is formed is described. The method for producing a solar cell according to claim 13, wherein the masking agent used in the pre-mask process has fluorine acid resistance and nitric acid resistance, and can be peeled off by an alkaline aqueous solution. The method for producing a solar cell according to claim 9 or 10, wherein in the process of forming the n-type diffusion layer, the hydrofluoric acid aqueous solution formed on the surface of the p-type diffusion layer can be removed. The film is used as a barrier film. The method for manufacturing a solar cell according to claim 9 or claim 10, wherein in the process of forming the front surface of the light-receiving surface electrode and the front-side bus electrode, the front-receiving surface electrode and the front bus are arranged. The electrodes are stacked in two layers to form a first electrode layer and a second electrode layer. The method for producing a solar cell according to claim 16, wherein the first electrode layer has a lower contact resistance with the tantalum single crystal substrate than the second electrode layer, and is different from the tantalum single crystal substrate. Then the intensity is strong. The method for producing a solar cell according to claim 16, wherein the second electrode layer has a volume specific resistance value lower than that of the first electrode layer. . Solar energy as stated in item 9 or item 10 of the patent application In the method of manufacturing a battery unit, the light-receiving surface electrode and the front bus bar electrode are formed by screen printing.