JPS6030180A - Amorphous thin film photovoltaic element - Google Patents

Abstract

PURPOSE:To obtain a photovoltaic element of high efficiency at the photovoltaic element having P-I-N structure by a method wherein the element is so constructed as to make the P type layer and the N type layer to have optically forbidden band widths larger than any part of the I type layer. CONSTITUTION:A P type amorphous silicon layer 3 introduced with carbon atoms, an intrinsic amorphous silicon layer 4, an N type amorphous silicon layer 5 introduced with carbon atoms, and a metal electrode 6 of high reflectivity are formed on a transparently conductive film 2 consisting of an ITO film, an SnO2 film or two layer film of the ITO film and the SnO2 film on a glass substrate 1. The P type layer 3 and the N type layer 5 become to junction type photovoltaic elements having larger optically forbidden band widths as compared with the I type layer 4, when light enters from the P type layer 3, light of long wavelength not absorbed completely at the I type layer 4 is not almost absorbed at the N type layer 5, but reflected by the Ag electrode 6, and absorbed again at the I type layer. It can be made as possible to make thickness of only the I type layer thin, and optoelectric conversion efficiency is enhanced.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an amorphous thin film photovoltaic device.

Structure of conventional example and its problems Recently, a thin film photovoltaic device mainly made of amorphous silicon has attracted attention as an inexpensive hL photovoltaic device. However, since the diffusion length of generated electrons and holes in amorphous silicon is very short, increasing the thickness of the iJ type amorphous silicon layer, which contributes to photovoltaic force, reduces the photoelectric conversion characteristics. Furthermore, if the film is made too thin, the light absorption rate will decrease and the photoelectric conversion efficiency will also decrease.For this reason, photovoltaic elements mainly made of amorphous silicon are generally made of crystalline photovoltaic elements. The photoelectric conversion efficiency is lower than that of conventional solar cells, and practical application has been delayed.

Purpose of the Invention The present invention alleviates the above-mentioned problems and provides a novel configuration for obtaining a highly efficient photovoltaic device. In a photovoltaic device having a p-1-n structure, an amorphous silicon film of a certain conductivity type doped with atoms such as oxygen atoms, an amorphous silicon film of an intrinsic type or close to an intrinsic type, a p-type layer and It is characterized in that the n-type layer has a larger optical band gap than any part of the type-1 layer. More specifically, the intrinsic (il-type layer is about ↓6) of the intrinsic layer used in conventional photovoltaic elements, and the diffusion of ``;n electrons and holes generated by absorbing light. It should be long enough and thick enough to be collected.

DESCRIPTION OF EMBODIMENTS The structure of the present invention and its manufacturing method will be described below with reference to the drawings.

In the figure, 1 is a glass substrate, and 2 is an ITO or Sn substrate.
○2 or a transparent conductive film consisting of a two-layer film of ITO and S n O2. On this transparent conductive film 2, a p-type amorphous silicon layer 3 into which carbon atoms are introduced is formed as a thin film having a thickness of, for example, about 10○ to 2Q○. To form this layer, S I H
A mixture of CH4 gas and B2H6 gas, for example, is used as the raw material gas.

The conditions at this time are, for example, B2H6 is 0.1 voA% with respect to S I H4, CH4 is about 50 vot%, and high frequency glow discharge is performed at a substrate temperature of 200 to 250°C. 4 is an intrinsic amorphous silicon layer with a thickness of about 2,000 to 4,000 mm, but since the amorphous silicon layer without impurities is an intrinsic type slightly close to n-type, the raw material gas is SIH4vC. ~60ppm 8 degrees B
In some cases, 2H6 is mixed to form the true form in the original sense. 6 is an n-type amorphous silicon layer into which carbon atoms are introduced;
To form this layer, a mixed gas of S i H4° CHPH is used, PH3 is about 1 voA% with respect to 5IH4413, and CH4 is S I H4
The number of participants will be approximately 50 vot%, and the number of participants will be approximately 100 to 300. 6 is a metal electrode with high reflectance, for example Aq
is formed to a thickness of approximately 0.1 to 1 μm using a vacuum evaporation method. In this way, the desired highly efficient photovoltaic device can be completed.

By adopting such a configuration, the p-type layer 3 and the n-type layer 5
becomes a junction photovoltaic element with a larger optical forbidden band than the L-type layer 4, and the light that enters from the P-type layer 3 is partially absorbed by the 1-type layer 4, and the long wavelength light that is not completely absorbed becomes the N-type. It is hardly absorbed by the layer 5, reflected by the Aq electrode 6, and absorbed again by the i-type layer. As mentioned above, since reflection on the back surface can be fully utilized, it is possible to reduce the thickness of the l-type layer that was previously required, and it is possible to compensate for the small diffusion length of amorphous silicon. Thus, a photovoltaic element with high photoelectric conversion efficiency can be obtained.

In the example, a photovoltaic element was shown in which a transparent electrode was formed on a glass substrate and light entered from the glass side and from the p-type layer, but a transparent electrode formed on a metal plate was shown. Light may also be introduced through the electrodes. Furthermore, instead of forming the p-type layer 3, i-type layer 4, and n-type layer 5 in this order, the n-type layer 5.
The mold layer 3 may be formed in this order. In addition, in the example, p-1-
Although the n single layer structure is shown, the same effect can of course be expected when a large number of p-1-n layers are stacked. Further, although the thin film is formed of amorphous silicon, other amorphous thin films may be used.

Effects of the Invention According to the present invention, it is possible to improve the light utilization efficiency as described above, and also to reduce the rate of recombination of electrons and holes generated by light, resulting in high conversion efficiency. A photovoltaic device is obtained. Moreover, since the type 1 layer can be made thinner, the productivity of the photovoltaic device is improved and costs can be reduced.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view showing an example of the configuration of a photovoltaic device according to an embodiment of the present invention. 1 Glass substrate, 2--Transparent conductive film, 3--P type layer, 4--Intrinsic type layer, 5 N-type layer, 6 Metal electrode.

Claims (1)

[Claims] It has a p-1-n structure consisting of an amorphous thin film formed on a substrate, and is characterized in that its p-type layer and n-type layer have a larger optical band gap than any part of the i-type layer. Amorphous thin film photovoltaic device.