JPH03136380A - Manufacture of photovoltaic device - Google Patents

Abstract

PURPOSE:To improve the output characteristics of a photovoltaic device by forming a semiconductor layer of one conductivity type on an i-type semiconductor layer after processing the surface of the i-type semiconductor layer by plasma discharge in a hydrogen atmosphere. CONSTITUTION:A p-type layer 3, i-type layer 4, and n-type layer 5 are successively formed by the plasma CVD method which is carried out by appropriately using raw gases of SiH4 gas, CH4 gas, B2H6 gas, PH3 gas, etc. During the course of forming the layers, the surface of the i-type layer 4 is processed by plasma discharge in a hydrogen atmosphere before the n-type layer 5 is formed after the layer 4 is formed. The plasma discharge is performed for about 10 to 20 minutes under a condition where the flow rate of the hydrogen gas, pressure, RF power, and substrate temperature are respectively controlled to 10-1,000 SCCM, 0.1-1.0Torr, 5-500mW/cm<2>, and 100-400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for manufacturing a photovoltaic device in which a semiconductor layer of one conductivity type is formed on an i-type semiconductor layer.

(b) Conventional technology As a photovoltaic device that directly converts light energy into electrical energy, amorphous materials such as amorphous silicon are used because they require less manufacturing energy and can be manufactured at low cost. Products using semiconductors are attracting attention.

Photovoltaic devices made of such amorphous semiconductors currently have problems with their output characteristics, especially low conversion efficiency, but as a means to solve this problem, we are trying to improve the interface characteristics of semiconductor junctions. It is thought that it can be improved.

For example, in a photovoltaic device with a pin structure, in which an amorphous silicon carbide layer is used as the p-type semiconductor layer, Journal Applied Phys.
sics 56(2), 15 July, 1984
538-542, by interposing a Daley-Braddle type amorphous silicon carbide layer between the p-type layer and the i-type layer, the carbon concentration gradually decreasing from the p-type layer to the i-type layer, The junction characteristics between the p-type layer and the i-type layer are improved to improve output.

(c) Problems to be Solved by the Invention By the way, in a photovoltaic device made of a pintll structure, after forming an i-type layer, it is necessary to form a p-type layer or an n-type layer on this layer. . In this case, impurities in the p-type layer or n-type layer diffuse into the i-type layer during its formation, deteriorating the characteristics of the junction interface.

This hinders the improvement of the output characteristics of the photovoltaic device. Conventionally, no measures have been taken regarding this point.

Therefore, an object of the present invention is to improve the junction interface characteristics by suppressing the diffusion of impurities into this l-type layer, thereby improving the output characteristics of a photovoltaic device.

(d) Means for Solving the Problems Method for manufacturing a photovoltaic device of the present invention; The method is characterized by comprising a step of forming a semiconductor layer of one conductivity type.

(E) Function According to the present invention, the surface of the type layer is treated by plasma discharge in a hydrogen atmosphere, so that impurities in the one conductivity type semiconductor layer formed thereon are removed from the type 1 layer. \Diffusion is suppressed and the bonding interface characteristics between the type 1 layer and the layer of one conductivity type are improved.

(f) Example FIG. 1 is a sectional view showing a photovoltaic device manufactured by the method of the present invention.

1 is a substrate made of a translucent material such as glass or heat-resistant plastic; 2 is a substrate made of a single layer or a laminate of a translucent conductive oxide (TCO) such as ITO or SnO+ formed on the substrate 1; 1 electrode film, 3 is a p-type layer made of amorphous silicon or amorphous silicon carbide formed on the first electrode film 2, and 4 and 5 are amorphous silicon laminated on the n-type layer 3. A second electrode film 6 is formed on the n-type layer 5 and is made of Ag or the like.

The p-type layer 3, i-type layer 4 and n-type layer 5 are made of SiH, gas, C
They are sequentially formed by a well-known plasma CVD method using appropriate raw material gases such as H, gas, B r 1 (- gas, PH, gas, etc.).

Here, the feature of the manufacturing method of the present invention is that after the formation of the type 1 layer 4 and before forming the n type layer 5, the surface of the type l layer 4 is treated by plasma discharge in a hydrogen atmosphere. be. This plasma treatment is performed at a hydrogen gas flow rate of 10 to 1100, for example.
08CC, pressure 0.1-1.0Torr, RF power 5
It is performed for about 10 to 20 minutes under conditions of -500 mW/cm' and a substrate temperature of 100 to 400°C.

FIG. 2 is a characteristic diagram showing the TV characteristic (broken line), which is the output characteristic of the photovoltaic device manufactured by the method of the present invention. For the surface of 4,
The IV characteristic solid line of a conventional photovoltaic device that does not undergo plasma treatment in a hydrogen atmosphere is also shown.

As is clear from the figure, according to the present invention, the open circuit voltage and form factor are each improved by about 5 to 6 lλ compared to the conventional example, and as a result, the output is improved by about 10%.

By the way, the reason why the above-mentioned improvement in output characteristics can be obtained by treating the IQQ10 surface with plasma discharge in a hydrogen atmosphere as in the method of the present invention is as follows.
Although it has not been elucidated at present, the present inventors speculate as follows.

In other words, regarding the surface state of the l-type layer 4, hydrogen atoms that exist alone without bonding with other atoms on the surface of the l-type layer 4 combine with hydrogen in the plasma, causing the hydrogen atoms in the l-type layer 4 to After removing the debris, type 1 layer 4
It is believed that the crystal structure on the surface of the layer 4 is in a rigid state, and that the dangling bonds present on the surface of the il-type layer 4 are compensated by hydrogen. By being in such a state, diffusion of impurities in the n-type layer 5 to the l-type layer 4 is suppressed, and the interface characteristics between the l-type layer 4 and the n-type layer 5 are improved.
Therefore, it is presumed that the recombination of carriers at the junction interface with the l-type layer 4 and the 11-type layer 5 is reduced, and the output characteristics of the photovoltaic device are improved.

In this example, a photovoltaic device having a structure in which the p-type layer 3, the l-type layer 4, and the n-type layer 5 are formed in this order has been described. The present invention can also be applied to a photovoltaic device having a configuration in which the formation order is reversed and the p-type layer 3 is formed on the l-type layer 4.

In addition, in the above embodiment, the substrate l is transparent, but
The present invention is not limited to this, and the substrate 1 may be made of a non-transparent material. In this case, the second electrode film 6 is composed of TCO. Effects of the Invention According to the manufacturing method of the present invention, after the surface of the l-type semiconductor layer is treated by plasma discharge in a hydrogen atmosphere, l
Since the one conductivity type semiconductor layer is formed on the one conductivity type semiconductor layer, it is possible to suppress the diffusion of impurities into the L type semiconductor layer and improve the bonding interface between the L type semiconductor layer and the one conductivity type semiconductor layer. , the output characteristics of the photovoltaic device can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a photovoltaic device formed by the manufacturing method of the present invention, and FIG. 2 is a characteristic diagram showing the IV characteristics of the photovoltaic device of the present invention and the conventional photovoltaic device. Figure 1

Claims (1)

[Claims] (1) A photovoltaic device characterized by comprising a step of treating the surface of the i-type semiconductor layer by plasma discharge in a hydrogen atmosphere, and then forming a semiconductor layer of one conductivity type on the i-type semiconductor layer. manufacturing method.