JPH0346377A - Solar cell - Google Patents

Abstract

PURPOSE:To set an electric field substantially perpendicular to a light incident direction and to eliminate weakening of the electric field even if the length of an optical path is increased by burying an I-type amorphous silicon layer between pyramidal P-type polycrystalline layers by using the pyramidal layers. CONSTITUTION:A transparent conductive film 2 having strong oxygen etching resistance of SnO2 formed on a transparent insulting board 1 made of glass, etc., is provided. A pyramidal P-type polycrystalline layer 3 is selectively formed on the film 2, an I-type amorphous silicon layer 4, an N-type amorphous silicon layer 5 and a rear surface metal electrode 6 are sequentially laminated on the film 2 and the layer 3, and the layer 3 is buried. Thus, an optical path is increased in length, light absorption amount is increased, and an electric field becomes substantially perpendicular as compared with a light incident direction. Thus, even if the length of the optical path is increased, the electric field is not weakened, thereby improving characteristics of a solar cell.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to an amorphous silicon solar cell using amorphous silicon.

(b) Conventional technology Solar cells are already known in which an amorphous silicon semiconductor layer with a semiconductor junction is used as a photoactive layer. An electrode layer, a semiconductor photoactive layer, and a back electrode layer are laminated in this order.

In order to improve the photoelectric conversion efficiency of such solar cells, Japanese Patent Laid-Open Nos. 58-57756 and 61-21817 have been proposed.
As disclosed in Publication No. 8, the surface of the light-receiving surface electrode layer on the light incident side is provided with irregularities of 0.1 μm or more and 2.5 μm or less to make the surface rough (textured) to lengthen the optical path length of the incident light. At the same time, there have been attempts to confine it in a photoactive layer.

(c) Problems to be Solved by the Invention In the above-described device, high effects are expected by making the photoactive layer thinner and lengthening the optical path. That is, it is important to make the electric field in the photoactive layer strong and to increase the amount of absorption, and it is desirable to make the unevenness as large as possible and to make the angle between the electric field and the incident direction large. For this reason, several μm
A transparent electrode with a prismatic structure is considered to be good.

However, when creating a prismatic structure as described above.

In particular, it is difficult to uniformly grow the thin film constituting the p-type layer.

An object of the present invention is to solve the above-mentioned problems and provide a solar cell in which large irregularities are formed on the light-receiving surface and a uniform thin film can be formed.

(d) Means for Solving the Problems The present invention selectively forms a prismatic p-type polycrystalline layer on a transparent conductive film provided on a transparent insulating substrate. It is characterized in that an i-type amorphous silicon layer, an n-type amorphous silicon layer, and a back metal electrode are sequentially laminated on the polycrystalline layer, and the p-type polycrystalline layer is embedded.

(e) Function The solar cell according to the present invention uses a prismatic p-type polycrystalline layer and an i-type amorphous silicon layer is embedded therebetween. Therefore, the electric field is approximately perpendicular to the direction of incidence of light, and the electric field does not become weaker even if the optical path length is increased.

(f) Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of the solar cell of the present invention.

In Figure 1, (1) is a transparent insulating substrate made of glass or the like, and (2) is a 5nOz substrate formed on the substrate (1).
This transparent conductive film (2) has a thickness of about 2000 Å. (3)
is a transparent p-type polycrystalline layer made of prismatic p-type silicon coverite or carbon selectively formed on the transparent conductive film (2). On this transparent conductive film (2) and p-type polycrystalline layer (3), a film with a thickness of 80 mm was formed by plasma CVD or the like.
I-type amorphous silicon layer (hereinafter abbreviated as a-5i) (4) N-type a-5i layer with a thickness of about 300A (
5) are sequentially laminated, and a p-type polycrystalline layer (3) is embedded. And Ag, AI.

A backside metal (6) consisting of Ti or a polycrystalline layer thereof is formed by vapor deposition.

In the solar cell of the present invention configured in this way, p
An i-type a-Si layer (4) is embedded between the type polycrystalline layers (3), and the electric field is approximately perpendicular to the direction of light incidence, so that the electric field does not weaken even if the optical path length is lengthened.

Next, an example of a method for manufacturing a solar cell according to the present invention will be explained with reference to FIG.

First, as shown in Figure 2 (a), a transparent conductive film (2) of 2000 mm thick with strong etching resistance such as SnO□ is formed on a transparent insulating substrate (11) made of glass etc. by CVD method etc. After that, p is applied on this transparent conductive film (2).
A transparent p-type polycrystalline layer (3) made of silicon carbide, carbon, or the like is formed by CVD. The thickness of this p-type polycrystalline layer (3) is 101 m.

Next, the substrate is transferred into a dry etching apparatus, and the p-type polycrystalline layer (3) is etched using oxygen plasma.

As a result of this etching, the polycrystalline layer (3) is etched from the top and interface, and as shown in Figure 2 (b), a prismatic p-type polycrystalline layer (3) is formed on the transparent conductive film (2). selectively formed.

Subsequently, as shown in FIG. 2(c), an i-type a-3i layer (4) with a thickness of 8000^, which is a photoactive layer, is formed, and a thick layer is formed on this i-type a-Si layer (4). 300 A n-type a
- Form a 3i layer (4). After that, Ag, A1. Or a back metal electrode made of Ti or a multilayer film thereof
(6) is formed by vapor deposition to form a solar cell according to the present invention.

A specific example of the above-mentioned manufacturing method will be described below.

First, a 5nOz film is formed as a transparent conductive film (2). The reaction conditions include a temperature of 500°C and a pressure cuff of 00T.
orr and using 5nC14 as the raw material gas, C
Formed by VD method.

Subsequently, a polycrystalline carbon layer is formed as a p-type polycrystalline layer (3). The reaction conditions were to keep the temperature at 650°C and the pressure at 100 Torr, and to use C1,
, Go, and H2 by microwave CVD. This output is 100W, and the gas mixture ratio is CH,・C
O□/H, was set to 1%. The p-type polycrystalline layer (3) is etched by oxygen plasma etching. The etching conditions are as follows: 02 is used as the etching gas at a temperature of 20° C., and the high frequency output is 50 W.

The formation conditions for the i-type a-3i layer (4) are: temperature 200°C;
The pressure was maintained at 0.3 Torr, and the flow rate was 101 as the raw material gas.
It was formed by plus CVD using SiH4 of 05e. The high frequency output at this time is 30W.

The n-type a-3i layer (5) is also maintained at a temperature of 200"C and a pressure of 0.3 Torr, and the flow rate of the raw material gas is 1010".
It was formed by plasma CVD using SiH4 and PH3 of 5e. The high frequency output at this time is 30W, PH
The mixing ratio of 3 was set at 1%.

The solar cell according to the present invention formed under the above conditions and n
The characteristics of each conventional solar cell using a type a-5i layer were measured. Figure 3 shows the output voltage characteristics of the solar cell of the present invention and the conventional solar cell under sunlight (AMl, 51). The results of comparing battery characteristics are shown.

Table 1 As is clear from FIG. 3 and Table 1, the solar cell of the present invention has (g
It can be seen that

(G) Detailed Description of the Invention As described above, according to the present invention, the optical path length is increased, the zero output of the light is increased, and the electric field is approximately perpendicular to the incident direction of the light, resulting in an increased optical path length. In other words, the electric field does not become weaker, and the characteristics of the solar cell are significantly improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of the solar cell of the present invention, FIG. 2 is a process diagram showing an example of the method for manufacturing the solar cell of the present invention, and FIG. 3 is a solar cell according to the present invention and a conventional solar cell. FIG. 3 is a characteristic diagram showing the output current-voltage characteristics of.

Claims (1)

[Claims] (1) A prismatic p-type polycrystalline layer is selectively formed on a transparent conductive film provided on a transparent insulating substrate, and an i-type amorphous silicon layer is formed on the transparent conductive film and the p-type polycrystalline layer. 1. A solar cell characterized in that a layer, an n-type amorphous silicon layer, and a back metal electrode are sequentially laminated, and the p-type polycrystalline layer is embedded.