JPS6242467A - Photoelectric conversion element - Google Patents

Abstract

PURPOSE:To obtain characteristics required for superior solar cell, by forming insulating films on the top and side faces at the peripheral part of a lower electrode so that the effect of leakage current at the peripheral part of a semiconductor film is remarkably reduced to increase an effective light-receiving area in comparison with the similar-sized substrate. CONSTITUTION:Amorphous semiconductor films 2, composed of a N-type layer 2a, non-doped layer 2b, and P-type layer 2c in the case of a pin-type element, are formed on a lower electrode 1 comprising a substrate of metal such as stainless steel, together with a transparent electrode 3 comprising a transparent electroconductive film like ITO, a metal collector pole 4, and an insulating film 5. The insulating film 5 is formed on the top and side faces at the peripheral part of the substrate 1. Because of the insulating film 5 in existence the P-type layer 2c does not come in direct contact with the lower electrode 1 even in case of its spreading, and therefore the leakage current at the end part can be remarkably suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an element structure for manufacturing a thin film photoelectric conversion element such as an amorphous solar cell with high conversion efficiency.

[Conventional technology]

FIG. 4 is a cross-sectional structural view of a photoelectric conversion element as a conventional amorphous solar cell formed on a metal substrate such as stainless steel, and FIG. 5 is an example of its surface view. In the figure, (1) is the lower electrode made of a metal substrate such as stainless steel, (
2) is an amorphous semiconductor film, for example, (2a) and (2b) in the case of a pin type element.

(2c) is an n-type layer, a non-bi layer, a p-type layer, and
(3) is I To (Induim -Tin-Oxi
(4) is a metal collecting electrode.

Usually, amorphous semiconductor Hf21 is produced by plasma CVD
Approximately I
The film is formed with about n remaining. Amorphous semiconductor film (2
), the n-type layer (2a) has a typical thickness of 200~
500 people, non-doped IW (2b) 4000-10
000 people, and the p-type layer (2c) has 100 to 300 people.

Next, the operation will be explained. Amorphous semiconductor film (2
) and the electrons generated by the light absorbed in the amorphous semiconductor film (2) are separated in opposite directions by the electric field present in the amorphous semiconductor film (2). In the case of a pin type element, holes are collected by a transparent electrode (3) and a metal collector electrode (4), and electrons are collected by a lower electrode (11), and are taken out as an external current.

In conventional photoelectric conversion elements, when the amorphous semiconductor film (2) is formed using a normal film formation method, it is inevitable that the film thickness will vary at the edges of the amorphous semiconductor film (2), and the film thickness will vary at the edges. This leakage current degrades the characteristics of the entire device. In particular, when forming the p-type layer (2c) under the conditions for plasma spreading in the plasma CVD method,
This results in a short circuit between the lower electrode (1) and the p-type layer (2c) or an increase in leakage current, which lowers the shunt resistance of the photoelectric conversion element and significantly deteriorates the characteristics of the photoelectric conversion element.

For the purpose of reducing series resistance and increasing VOC, a microcrystalline layer having a high conductivity of lo-1 to IOΩ-'IJ-' is used as a doping layer for the p-type layer (2c) and n-type layer (2a). is often used, but in this case the influence of the edges becomes even more noticeable. Even if the amorphous semiconductor film (2) is formed over the entire surface of the lower electrode (1) in order to eliminate fluctuations in film thickness at the edges, a similar effect will occur on the side surfaces of the lower electrode (1).

[Problem that the invention seeks to solve]

Since the conventional photoelectric conversion element is constructed as described above, when the element is manufactured only by a mask process, the transparent electrode (3) and the n-type layer (2a
) or the lower electrode (1), and in order to avoid this and to reduce as much as possible the influence of the leakage TL flow due to the edge of the amorphous semiconductor film (2), the transparent electrode (3) There was a problem in that the masking method was used to form the amorphous semiconductor film (2) more than 11 times further inside than the edge of the amorphous semiconductor film (2), thereby sacrificing the effective light-receiving area.

This invention was made to solve the above-mentioned problems, and it significantly reduces the influence of leakage current at the periphery of an amorphous semiconductor film, expands the effective light-receiving area for a substrate of the same size, and improves performance. The purpose of the present invention is to obtain a photoelectric conversion element that can obtain characteristics as a solar cell.

[Means for solving problems]

In the photoelectric conversion element according to the present invention, an insulating film is formed on the surface and side surfaces of the peripheral part of the lower electrode, so that the transparent electrode and the lower electrode do not come into direct contact in the peripheral part of the lower electrode. .

[Effect]

In the photoelectric conversion element of the present invention, by providing an insulating film around the lower electrode, leakage current at the edge of the amorphous semiconductor film is significantly reduced, and contact between the transparent electrode and the lower electrode is impossible. Therefore, it is possible to expand the transparent electrode to the size of the substrate, and by increasing the effective light-receiving area, it is possible to obtain device characteristics with high conversion efficiency.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, (11 is a lower electrode made of a metal substrate such as stainless steel, (2) is an amorphous semiconductor film, and pin
For type elements, (2a), (2b), (2c)
are an n-type layer, a non-doped layer, a p-type layer, and (3) is an I layer, respectively.
A transparent electrode made of a transparent conductive film such as TO, (4) a metal collector electrode, and (5) an insulating film. The insulating film (5) is the substrate (1)
It is formed on the surface and sides of the periphery. Due to this insulating film (5), even if the p-type layer (2c) spreads, it will not come into direct contact with the lower electrode (1), and leakage current at the ends can be significantly suppressed.

Furthermore, in the photoelectric conversion element of this example, the film formation region of the amorphous semiconductor film (2) and the region of the transparent electrode (3) can be expanded over the entire substrate fl1. FIG. 2 is an enlarged sectional view of the peripheral portion E in that case. It is assumed that the inside of the lower electrode +11 is covered by a length l from the end thereof with an insulating film (5), and this area is called I, and the effective area inside it is called mouth. Because the non-doped layer (2b) is inserted,
There is little possibility that the p-type layer (2c) or the transparent electrode (3) and the n-type layer (2a) will come into contact with each other at the end, but if the transparent electrode (3) comes into contact with the n-type JiJ (2a) and this Let us find the length of l as a sufficient condition that at least the device characteristics in the effective region (2) are not degraded when there is an individual current through the channel. Assuming that all the current generated in region ■ flows through the path shown by the dotted line and becomes a leakage current,
Since points A and B on the transparent electrode (3) are almost at the same potential, the above sufficient condition is that the potential at point B (potential at point A) is at least as low as the operating voltage of the element compared to the potential at point 0. The condition is that it should be higher than ゛. As the n-type layer (2a), a microcrystalline layer with a conductivity of 1Ω-'(J-'
Assuming that the operating voltage of the element when used in a human thin film is approximately 0.5 square meters, and the short circuit current in region P is J, co+A/cIIl, the above conditions are expressed by the following equation.

10'/3 ・1" XJsc≧0.5 ---
・+1! From this conditional expression fll, for example, Jsc is 5mA
/-, l is 1.7 XIQ-'cm or more, JIC
When is 10mA/cd, l is 1.2 XIQ-”am
Anything above this will lead to something good. Therefore, even if Jo is 5 mA/-, if β is set at 0.2, even if the transparent electrode (3) and the n-type layer (2a) are in contact, the characteristics of the effective area (2) will be adversely affected. There isn't.

In this way, with the photoelectric conversion element of the present invention, the effective area can be expanded to almost the entire surface, whereas in the past, the effective area could only be secured about 1 to 2 degrees inside from the periphery.
Since neither the amorphous semiconductor film (2) nor the transparent electrode (3) requires a mask during formation, there is an advantage that the manufacturing process can be simplified.

As the insulating film (5), for example, Sin! Membrane, S i 3
Na film etc. as the lower electrode! Alternatively, a polymer film such as polyimide may be formed on the lower electrode (1) in advance. It is desirable that the insulating film (5) has no pinholes and has a withstand voltage several times the open circuit voltage of the element. Therefore, the insulating film (5)
The film thickness is preferably about 100 to 1/Jm.

FIG. 3 shows a charging conversion element according to another embodiment of the present invention. In the photoelectric conversion element of the example shown in FIG.
The insulating film (5) is formed around and on the side of the lower electrode (1) before the amorphous semiconductor film (2) is formed.
After forming the amorphous semiconductor film (2), the transparent electrode (3)
The light of this example whose periphery and side surfaces were covered with an insulating film (5) before the formation of the light! Almost the same effect can be obtained with the conversion element.

In each of the above embodiments, a photoelectric conversion element was shown in which an n-type layer, a non-doped layer, and a p-type layer were formed in order from the lower electrode side as an amorphous semiconductor film. Exactly the same structure can be applied to a photoelectric conversion element in which a mold layer is formed, and also to an element using a Schittky junction or a heterojunction.

Furthermore, although amorphous St is currently most widely used as an amorphous semiconductor film, amorphous Si
Similar effects can be obtained when using alloys such as C, amorphous SiN, amorphous 5iGe, and amorphous Sign.

Further, in each of the above embodiments, the case of a single layer element has been described, but it is clear that the same effect can be achieved in the case of a multilayer structure element in which single layer elements are laminated.

Further, in each of the above embodiments, a metal substrate is used as the lower electrode, but a metal film formed on a non-metallic substrate may be used as the lower electrode.

〔Effect of the invention〕

As described above, according to the present invention, since the insulating film is provided in a small area around the lower electrode, the leakage current at the edge can be significantly reduced, and the effective area can be extended to the size of the substrate. This has the effect of making it possible to bring the photoelectric conversion element close to each other, resulting in a photoelectric conversion element with high output.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a photoelectric conversion element according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a main part of the photoelectric conversion element shown in FIG. 1, and FIG. 3 is a cross-sectional view of a photoelectric conversion element according to another embodiment of the present invention. A cross-sectional diagram of a photoelectric conversion element, FIG. 4 is a cross-sectional structural diagram of a conventional photoelectric conversion element,
FIG. 5 is a surface view of the photoelectric conversion element shown in FIG. 4. (11 is the lower electrode, (2) is the amorphous semiconductor film, (
2a) is an n-type layer, (2b) is a non-doped layer, (2c) is a p-type layer, (3) is a transparent electrode, (4) is a metal collector electrode, (5)
) is an insulating film. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A photoelectric conversion element having a metal substrate or a metal film formed on the substrate as a lower electrode, the photoelectric conversion element comprising an insulating film covering the periphery and side surfaces of the lower electrode.