JPH05218466A - Manufacture of photovoltaic element - Google Patents

Abstract

PURPOSE:To enable a photovoltaic element, which is high enough in strength and where a V-shaped groove and a bulk layer are surely controlled in angle and thickness respectively, to be produced in a simple manufacturing process. CONSTITUTION:A large number of V-shaped grooves 1a, 1a,... are provided in parallel with each other onto the surface of a base material 1 of single-crystal silicon, and then an insulating film pattern 2 different from silicon in refractive index is formed thereon, and a single-crystal silicon thin film 3 of one conductivity type is formed thereon through a liquid growth method (LPE), and a silicon thin film 4 of another conductivity type is formed thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a photovoltaic device for converting light energy into electric energy.

[0002]

2. Description of the Related Art In a crystalline silicon thin solar cell, for the purpose of sufficiently absorbing light, for example, as in a corrugated solar cell shown in FIG. 4, a V-shape is formed on both sides of a p-type single crystal silicon substrate a. There is a structure in which a plurality of mold grooves b, b, ... Are formed in parallel, whereby the reflected light is effectively used to confine the light (Con.
f.Rec.20th IEEE Photovolt. Special.Conf. (1988), p
p 792 to 795 (Central Research Laboratory, Hitachi, Ltd.)). In FIG. 4, c is a p ⁺ type layer, d is an n ⁺ type layer,
Reference numeral e represents a silicon oxide film, f represents a front surface electrode, and g represents a back surface electrode.

[0003]

The V-grooves b, b, ... Are formed by subjecting both sides of the single crystal silicon substrate a to alkaline anisotropic etching. In the structure having the grooves b, b, ..., The manufacturing process is complicated, and it is difficult to control the angle of the V grooves b, b, ... And the thickness of the bulk layer of the solar cell. Moreover, since the thickness of the single crystal silicon substrate a after forming the V-grooves b, b, ... Is about 50 μm, there is a problem that the strength is insufficient and it is easily cracked.

The present invention has been made in view of the above conventional problems, is easy to manufacture, and is sure to control the angle of the V groove and the thickness of the bulk layer, and has sufficient strength. An object of the present invention is to provide a method for manufacturing a photovoltaic element having

[0005]

According to the method of manufacturing a photovoltaic element of the present invention, a substrate having a plurality of fine V-shaped grooves formed in parallel with each other on the surface of crystalline silicon has a refractive index of silicon and that of silicon. It is characterized in that patterns of different insulating films are formed, a silicon thin film of one conductivity type is formed thereon by a liquid phase growth method, and then a silicon thin film of another conductivity type is formed on this silicon thin film.

[0006]

According to the manufacturing method of the present invention, since it is only necessary to form the V groove only on the crystalline silicon surface of the base substrate,
The manufacturing process is simple. Therefore, the angle of the V groove and the thickness of the bulk layer can be reliably controlled.

Further, since the V groove is formed only on one surface of the base substrate, the thickness of the base substrate can be secured to a sufficient strength, and thus the base substrate can act as a supporting substrate,
It has a strong structure.

By forming a pattern of an insulating film such as a silicon oxide film (SiO ₂ ), it is possible to reduce the surface recombination rate by point contact and to confine light at the same time due to the difference in refractive index between silicon and the silicon oxide film. Furthermore, by setting the base substrate to have a low resistance, it is possible to achieve a back surface BSF (Back Surface Field).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a structural diagram of a solar cell including a photovoltaic element according to the present invention. Specifically, the solar cell is an amorphous silicon (a-Si) / single crystal silicon using a single crystal silicon film. It is a heterojunction solar cell.

In FIG. 1, reference numeral 1 is a base substrate made of low-resistance (n ⁺ ) single crystal silicon, on the surface of which a large number of V-shaped grooves 1a, 1a, ... Are formed in parallel. Reference numeral 2 is an insulating film having a refractive index different from that of silicon, such as silicon oxide (SiO ₂ ). The insulating film 2 is provided on the substrate 1 as shown in the figure and is patterned so that the surface of the substrate 1 is partially exposed. .. In this embodiment, patterning is performed so that the surface of the substrate 1 at the bottom of the V-shaped grooves 1a, 1a is exposed. Reference numeral 3 is an n-type single crystal silicon thin film, 4 is a p-type amorphous silicon thin film, and the junction interface between the n-type single crystal silicon thin film 3 and the p-type amorphous silicon thin film 4 contributes as a power generation layer. 5 is a transparent conductive film, 6 is a back electrode,
Reference numeral 7 is a front side extraction electrode. The incident direction of the light A is the side opposite to the base substrate 1 as shown in the figure.

Next, a method of manufacturing the photovoltaic element will be described with reference to FIGS. First, the V-shaped grooves 1a, 1 are formed on the surface of the base substrate 1 by mechanical etching.
After a large number of a, ... Are formed in parallel (see FIG. 2 (a)), an insulating film 2 made of silicon oxide is formed on this surface, and V
Patterning is performed so that the surface of the substrate 1 at the bottom of the V-shaped grooves 1a, 1a is exposed (see FIG. 2B). Then, n is formed on the insulating film 2 by liquid phase epitaxy (LPE) or the like.
A type single crystal silicon thin film is formed by lateral seeding epitaxy.
(See Figure 2 (c)). Then, the n-type single crystal silicon thin film 3
A p-type amorphous silicon thin film 4 is formed thereon by the LPCVD method or the like (see FIG. 3 (a)), and the junction interface between the n-type single crystal silicon thin film 3 and the p-type amorphous silicon thin film 4 becomes a power generation layer. After that, a transparent conductive film 5 such as TCO is provided on the p-type amorphous silicon thin film 4 (see FIG. 3).
(See (b)). Then, the extraction electrode 7 is formed on the transparent conductive film 5.
Then, the back electrode 6 is formed on the back surface of the substrate 1 to obtain the photovoltaic element shown in FIG.

By the way, since the electrode extraction on the n-type single crystal silicon thin film 3 side is performed through the region where the surface of the substrate 1 at the bottom of the V-shaped grooves 1a, 1a contacts the exposed portion, point contact is made. Therefore, the surface recombination rate is reduced. Further, it has an optical confinement effect due to the difference in refractive index between silicon and the silicon oxide film.

Next, Table 1 shows the results of the photovoltaic characteristic test conducted on the solar cell (invention product) having the above-mentioned structure in comparison with the solar cell by the conventional method (conventional product).

The product of the present invention used in this test has the structure shown in FIG. 1, and the p-type amorphous silicon film 4 is formed on the power generation layer 3 formed by the above method under the conditions shown in Table 2. It is formed by and joined. Further, the conventional product is one in which V-grooves are formed on both sides of an n-type single crystal silicon substrate by a conventional method, and an n-type amorphous silicon film is formed thereon to form a junction.

[0015]

[Table 1]

[0016]

[Table 2]

As is clear from Table 1, the product of the present invention is V
It was found that the conversion efficiency comparable to that of the conventional product can be obtained even though the V-shaped grooves 1a, 1a, ... Are formed only on the front surface side of the base substrate 1.

The present invention is not limited to the above-mentioned embodiment, and various design changes can be made. For example, in the illustrated example, a single crystal silicon substrate is used as the base substrate 1, but in addition to this, a cast polycrystalline silicon substrate can also be used, or after the surface of the metal plate is covered with an amorphous silicon film, A structure formed by crystallizing an amorphous silicon film may be used.

[0019]

As described in detail above, according to the present invention,
A pattern of an insulating film having a different refractive index from that of silicon is formed on a substrate in which a number of fine V-shaped grooves are formed in parallel on the surface of crystalline silicon, and a silicon thin film is laterally seeded epitaxially thereon. Since it is formed, it is possible to simplify the manufacturing process while ensuring the same conversion efficiency as that of the conventional method, and to control the angle of the V groove and the thickness of the bulk layer with certainty.

By forming the V groove only on one surface of the base substrate, the thickness of the base substrate can be secured to a sufficient strength, and the base substrate can be provided with a function as a supporting substrate. It is possible to obtain a strong structure.

Furthermore, by forming a pattern of an insulating film such as a silicon oxide film (SiO ₂ ), it is possible to reduce the surface recombination rate by point contact and simultaneously confine light by the difference in the refractive index of silicon and the silicon oxide film. In addition, the back surface BSF can be achieved by setting the underlying substrate to have a low resistance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a heterojunction solar cell which is an embodiment according to the present invention.

FIG. 2 is a cross-sectional view for each step for explaining a method for forming a power generation layer in the same heterojunction solar cell.

FIG. 3 is a cross-sectional view for each step for explaining a method for forming a power generation layer in the same heterojunction solar cell.

FIG. 4 is a view showing a structure of a corrugated solar cell which is a conventional crystalline silicon thin solar cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base substrate made of n-type single crystal silicon 1a V-shaped groove 2 Pattern of insulating film made of silicon oxide 3 Power generation layer made of single crystal silicon thin film 4 p-type amorphous silicon film 5 transparent conductive film 6 back electrode 7 surface Electrode A light

Claims (3)

[Claims] 1. A pattern of an insulating film having a refractive index different from that of silicon is formed on a substrate having a plurality of fine V-shaped grooves formed in parallel on the surface of crystalline silicon, and a pattern of one conductivity type is formed thereon. A method for manufacturing a photovoltaic element, comprising forming a silicon thin film by a liquid phase epitaxy method and then forming a silicon thin film of another conductivity type on the silicon thin film. 2. The method for manufacturing a photovoltaic element according to claim 1, wherein the substrate is a cast polycrystalline silicon substrate. 3. The method of manufacturing a photovoltaic element according to claim 1, wherein the substrate is obtained by covering the surface of a metal plate with an amorphous silicon film and then crystallizing the amorphous silicon film.