JPH0456170A - Manufacture of thin-film solar cell - Google Patents

Abstract

PURPOSE:To obtain a sufficient open-circuit voltage by means of a thin microcrystalline p-layer and to increase a short-circuit current by a method wherein, after the surface of the p-layer has been plasma-doped with acceptors, an interface layer is laminated. CONSTITUTION:A microcrystalline silicon p-layer 3 is formed on a transparent electrode 2 on a glass substrate. Then, when a plasma-doping operation is executed, a plasma-doping layer 8 is produced. In succession, an a-SiC interface layer 4 is formed. In addition, an i-layer 5 and an n-layer 6 are formed. Lastly, a rear electrode 7 is formed. In this case, the surface of the layer 3 is plasma- doped with acceptors, and the layer 4 is laminated on it. Then, the acceptors are diffused to the layer 4 during the formation process of the layer 4, and the good-quality p-layer which does not contain any impurities is formed. Accordingly, even when the layer 3 is thin, it is possible to obtain a sufficient diffusion potential between it and the layer 5. As a result, a sufficient open circuit voltage value is obtained. Since the layer 3 is thin, a short circuit current is increased. Since also a curve factor is high, a high conversion efficiency can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a thin film solar cell mainly composed of amorphous silicon (hereinafter abbreviated as a-5i).

[Conventional technology]

Microcrystalline silicon has low light absorption and conductivity of a-
3i, amorphous silicon carbide (a-5ic)
Because it is extremely small compared to , it is attracting attention as a window layer on the light incident side of a-3i solar cells.

As shown in FIG. 2, such a solar cell is made of a transparent conductive material such as SnO□ on a transparent insulating substrate 1 such as glass, and a transparent electrode 2 coated with ZnO or the like to increase plasma resistance. Next, a p-type microcrystalline silicon layer 3 is formed by a plasma CVD method using Sih as a main gas, h as a diluent gas, and BIH& as a doping gas.

Next, use 5ine as main gas and H8 as diluent gas for 1l.
ia-5i layer 5 is formed, and SiH* is the main gas, h
n@a- with dilution gas and -Pus as doping gas.
In the structure shown in Fig. 0, which is fabricated by forming a 3i layer 6 and finally a metal back electrode 7, non-doping or a trace amount of boron doping is performed between the second layer 3 and the first layer 5. An interface layer 4 made of a-3iC is formed, which mainly improves the open circuit voltage.

[Problem to be solved by the invention]

When ordinary microcrystalline silicon obtained by plasma CVD method with high hydrogen dilution and high discharge power is applied to the window layer of the solar cell shown in Figure 2, the film thickness must be considerably thick to obtain a sufficient diffusion potential. For example, Figure 3 shows the film thickness dependence of 9 microcrystalline layers in a single cell with 5,000 people per layer. is required. This is because impurities are considerably diffused from the transparent electrode 2 into the microcrystalline p layer 3 when performing plasma CVD with high hydrogen dilution and high discharge power.
This seems to be based on the fact that a good quality p layer cannot be formed unless the 9 layer 3 is formed thickly. For this reason, a cell using microcrystalline silicon for the window layer has a higher fill factor (FF) than a cell using ordinary a-3iC for the window layer, but the short-circuit current (
Jse) was low, and as a result, the conversion efficiency was lower than that of a cell using a-5iC in the p layer.

An object of the present invention is to solve the above-mentioned problems and provide a method for manufacturing a thin film solar cell in which a sufficient open circuit voltage can be obtained with a thin microcrystalline p-layer and a short circuit current can be increased.

(Means for solving !l111) In order to achieve the above object, the present invention has a p1nil layer, and has one layer made of a-5i and a layer made of microcrystalline silicon on the light incident side of the layer. In a method for manufacturing a thin film solar cell in which an interface layer made of a-3iC is interposed between p-layers and is undoped or doped with a small amount of acceptor, a microcrystalline 99379 layer is formed on a transparent insulating substrate via a transparent electrode. Then, an acceptor is plasma-doped from the surface of the p-layer, and then an interface layer is laminated.

[Effect]

When acceptors are plasma-doped from the surface of the microcrystalline SIP layer and an a-5iC interface layer is laminated on top of it, the acceptors diffuse into the interface layer during the interface layer formation process, forming a high-quality p-layer free of impurities. Therefore, even if the microcrystalline 99379 layer is thin, a sufficient diffusion potential can be obtained between it and the i-layer.

(Example) Figure 1 shows a thin film solar cell according to an example of the present invention.
Parts common to those in the figures are given the same reference numerals. This solar cell is manufactured as follows.

First, 5IIO on the glass substrate l! Then, ZnO was evaporated to increase plasma resistance to form a transparent electrode 2, and a microcrystalline 99379 layer 3 was deposited on the transparent electrode 2 at 100% by plasma CVD using 5ide as a main gas, H2 as a diluent gas, and Bz[l* as a doping gas. Form to the thickness of a person.

Hydrogen dilution degree (H) / (Si
H#] is about 100 to 200 times higher, and the RF power is 5 to 10 times higher than that of normal a-5t layer formation. Plasma doping is performed by RF discharge for 30 seconds to 10 minutes, resulting in a plasma doped layer 8. Next, it's expensive ■. . In order to obtain
An interface layer 4 of a to SiC is formed to a thickness of 100 layers using CL as a main gas and H2 as a diluent gas. Furthermore, one layer 5 is 5
000 people, Sino as main gas, H2 as diluent gas, PH1
A solar cell is produced by forming the 0 layer 6 to a thickness of 150 mm using doping gas, and finally forming the back electrode 7 of Ag by vapor deposition.

The plasma doping time dependence of the cell characteristics of this solar cell is shown in FIG. It is known that even if plasma doping is performed for a longer period of time, the characteristics are saturated and will not deteriorate. Therefore, by increasing the plasma doping time to a certain extent, extremely uniform characteristics can be obtained. It is possible to create cells of Therefore, next time, the plasma doping time was set to 5 minutes, and the microcrystal 9
The film thickness dependence of 9379 layer 3 was investigated. From the results shown in FIG. 5, it can be seen that a sufficient p layer is formed with a microcrystalline silicon film thickness of 50 Å or more.

Since the microcrystalline silicon film thickness can be reduced to 100 Å or less,
A high short circuit current of mA/- or more can be obtained, and microcrystalline silicon has a low resistance, so the fill factor is as large as 0.76 or more.As a result, when the microcrystalline silicon film thickness is 50 and 75 people, , a conversion efficiency of 13% was obtained.

In wA61 of FIG. 6, a cell l according to another embodiment of the present invention is shown.
-V characteristics. In this case, a microcrystalline silicon carbide film having a thickness of 70 mm is applied to the p-type microcrystalline silicon film 3 shown in FIG. Microcrystalline silicon carbide uses StH*, Cut as main gas, H2 as diluent gas, and BAH.
, as the doping gas and hydrogen dilution (H) / (S
iH*) = 200 times. The optical absorption of this microcrystalline silicon carbide is about 1 that of microcrystalline silicon.
72, which results in a high J! of 19.7mA. c and conversion efficiency of 13.3% (Vac-0,8
9V, J sc"'19.7-^/aJ,
FF=0.76) was obtained. In addition,! The efficiency of the cell without plasma doping shown in i62 is 9
．． 0% (vo.

"0.75V, Jsc=18.4mA/d, FF-
0.65).

〔Effect of the invention〕

According to the present invention, microcrystals 2937 exist as a window layer of a pin structure with an a-SiC interface layer sandwiched therebetween.
After the formation of the 9 layers, acceptor plasma doping is performed to form a high-quality p-layer in the interface layer stacked on top of the acceptor. The influence of impurities could be avoided. As a result, a sufficient open circuit voltage is obtained, and the short circuit current is increased due to the thinness of the microcrystalline 29379 layer, and together with the high fill factor, a high conversion efficiency is achieved. Furthermore, since the plasma doping time can be extended, it is easy to produce cells with uniform characteristics. Therefore, it is extremely effective as a method for manufacturing large area A-5T solar cells for power use.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a thin-film solar cell according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a thin-film solar cell according to a conventional method, and FIG.
Figure 4 is a diagram showing the relationship between the characteristics of a thin-film solar cell and the thickness of a microcrystalline silicon layer according to a conventional method. FIG. 5 is a diagram showing the relationship between the characteristics of a thin film solar cell according to an embodiment of the present invention, plasma doping time, and the thickness of a microcrystalline silicon layer, and FIG. It is a current/voltage characteristic diagram of a solar cell. 1: glass substrate, 2: transparent electrode, 3: two microcrystalline silicon p
Layer, 4: Interface layer, 5: 1a-5i layer, 5
: n-a-3i layer, 7: Back electrode, 8: Plasma doped layer. Daiton Patent Attorney Yamaguchi Hoshi 2nd figure Atsushi I product Shiryun p4! 10 (persons) Figure 6

Claims (1)

[Claims] 1) It has a pin structure and is made of amorphous silicon carbide and is non-doped or doped with a trace amount of acceptor, existing on the light incident side of the i-layer made of amorphous silicon and between the p-layer made of microcrystalline silicon. In a method for manufacturing a thin film solar cell with an intervening interface layer, a microcrystalline silicon p layer is formed on a transparent insulating substrate via a transparent electrode, an acceptor is doped from the surface of the p layer, and then an interface layer is formed. A method for manufacturing a thin film solar cell characterized by stacking layers.