JPS616873A - Photovoltaic element - Google Patents

Abstract

PURPOSE:To improve photoelectric conversion efficiency and the quality of a product by increasing an optical band gap, reducing optical absorption and easily obtaining a low resistance layer by constituting a photovoltaic element by a hetero-junction between an oxide semiconductor film and an amorphous semiconductor film. CONSTITUTION:A transparent conductive film 2, an oxide semiconductor layer 3, an I type a-Si layer 4, a P type a-Si layer 5 and a back electrode film 6 are laminated, formed and constituted onto a light-transmitting insulating substrate 1 in the order, and structure containing a hetero-junction between the oxide semiconductor layer 3 and the I type a-Si layer 4 is shaped. Both the oxide semiconductor films have optical band gaps of 2.0eV or more, and both of resistivity thereof are set to order or less of 10<-1>OMEGAcm. Known methods, such as the mixing of an impurity, the alteration of a composition ratio, etc. may be adopted in order to reduce the resistivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photovoltaic element used as a solar cell or the like.

[Prior art]

Generally, an amorphous solar cell is constructed by laminating a transparent conductive film, an amorphous silicon layer, and a metal electrode film on a transparent insulating substrate. A p-type amorphous silicon layer (denoted as p-type a-5iC) is arranged to form a heterojunction with i-type amorphous silicon (denoted as l-type a-3i) jif.

By the way, in the case of an amorphous solar cell, it is desirable for the layer on the light incident side of the amorphous silicon layer to have low light absorption, in other words, a wide optical bandgap, and low resistance in order to improve the characteristics. In the case of P-type a-5iC as described above, increasing the C content widens the hand gap and reduces light absorption, but at the same time there is a problem in that the resistance increases. On the other hand, if the resistance is lowered by increasing the amount of doping with, for example, boron, there is a problem that the hand gap becomes smaller and light absorption loss increases.

〔the purpose〕

The present invention was made in view of the above circumstances, and its purpose is to focus on the fact that oxide semiconductors have a wide optical hand gap and have a low resistance of 117 J. It is an object of the present invention to provide a photovoltaic device whose characteristics can be significantly improved by configuring the dove surface on the incident side.

〔composition〕

The photovoltaic device according to the present invention is characterized by having a heterojunction between an oxide semiconductor layer and an amorphous semiconductor layer.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. The drawing shows a cross-sectional structural diagram of a photovoltaic device according to the present invention (hereinafter referred to as the "invention product") together with a hand structural diagram, in which 1 is a transparent insulating substrate made of glass or the like, and 2 is a transparent insulating substrate. A conductive film, 3 an oxide semiconductor layer, 4 an i-type a-
3i layer, 5 is a p-type a-3i layer, and 6 is a back electrode film.

In the photovoltaic device of the present invention, a transparent conductive film 2, an oxide semiconductor Jii 3, an l-type a-3i layer 4, a p-type a-5i layer 5, and a back electrode film 6 are formed on a transparent insulating substrate 1 in this order. It is configured by stacking layers, and has a structure including a heterojunction between an oxide semiconductor layer 3 and an i-type a-3i layer 4.

The oxide semiconductor layer has an optical band gap of 2.
OeV or more and TiO2, ZnO, CdO, MgO
.

Cu20. Fed, Fe20'3, n-type TiO2, n-type ZnO, n-type CdO, n-type made of NiO, etc.
Type MgO, p type Cu2O, p type Fed, 1) type Fe
It is formed using 2O3, p-type NiO, etc., using a thermal CVD method, a sputtering method, or the like.

All of these oxide semiconductor films have an optical band gap of 2. OeV or more, and their resistivities are all set to be on the order of 10-1 Ωσ or less. To reduce this resistivity, conventionally known methods such as mixing impurities or changing the composition ratio may be employed.

By the way, the bandgap of n-type TiO2 is 3.2 eV, which is larger than 1.9 to 2.0 for the a-3i layer, and the resistivity is on the order of 10-1 Ωcm, which is the resistance of the i-type a-3i layer. By using this, a doped layer with less light absorption and low resistance can be obtained.

Furthermore, when using n-type TiO2, the binding energy of Ti-0 (160ca A/mo1) is 132ca11/m of 5n-0 of 5n02 of transparent conductive film 2.
oj! Since it is larger, the diffusion of 0 atoms into the a-3i layer is smaller than that of the conventional one, resulting in less deterioration of photoelectric conversion performance.

Note that other layers, i.e., one layer when using n-type TiO2, etc.
1 when using pJiit or p-type Cu20, etc.
For both the layer and the 0 layer, a conventionally known layer such as an a-3i layer may be used.

On the lower side of the drawing, n-type TiO2 is used as the doped layer on the light incidence side, and the n-type TiO2 layer, i-type a-3 upper layer, and p-type a-5i
1 is a diagram showing an optical bandgap of a photovoltaic element according to the present invention formed by laminating layers, and is shown in correspondence with a cross-sectional structure diagram. In the figure, A indicates a transmission band B indicates a valence band, a dashed line indicates a fuel mile, black circles indicate electrons, and white circles indicate holes.

As is clear from this drawing, the optical energy gap of the n-type TiO2 doped layer is i-type a-3i.

It is larger than that of p-type a-5i, and therefore the incident light is not absorbed in the n-type TiO2 layer, and the i-type a-5i
It can be seen that the photoelectric conversion characteristics can be improved by making the light incident on the layer.

In the above embodiment, the oxide semiconductor film is arranged on the transparent conductive film 2 side, which is the light incident side. Of course, a configuration may also be used.

〔effect〕

As described above (because the product of the present invention is composed of a heterojunction between an oxide semiconductor film and an amorphous semiconductor film, it has a high optical hand gap, little light absorption, and a low-resistance layer). is easy to obtain, improves photoelectric conversion efficiency, and improves product 1.
The present invention has excellent effects such as improving quality.

[Brief explanation of the drawing]

The drawing is a drawing showing both a cross-sectional structure diagram and a band structure diagram of the product of the present invention.

Claims (1)

[Scope of Claims] 1. A photovoltaic device characterized by having a heterojunction between an oxide semiconductor layer and an amorphous semiconductor layer. 2. Claim 1, wherein the heterojunction is a junction between an n-type or p-type oxide semiconductor layer and an i-type amorphous semiconductor layer.
Term electromotive force element described in Term. 3. The photovoltaic device according to claim 1, wherein the n-type oxide semiconductor layer is an n-type TiO_2 layer.