JPS63287077A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE:To increase a photoelectric conversion efficiency, by making a contact region of an electrode collecting a small number of carriers and a semiconductor finger-shaped for increasing a contact area with the electrode surface. CONSTITUTION:The surface of a p-type semiconductor layer 11 and its back are oxidized to form oxide films 10 and 9. A resist mask is formed on the oxide film 9 on the back and having this as a mask, a finger-shaped groove for forming n<+>-type semiconductor regions 5 and the holes for forming p<+>-type semiconductor regions 6 are opened. Further, P and BF2 ions are implanted into the respective holes for forming conductors in order to form the regions n<+> and p <+>. Subsequently, heat treatment is performed for activation to form the regions 5 and 6. Next, composite finger-shaped electrodes of Ti/Ag are formed in the regions 5 and 6, while forming a reflection preventive film 10 on the light incident surface of the back. Thereby, the collection and the taking-in of a small number of carriers from a bulk semiconductor layer to the pn junction regions are effectively performed so as to increase the photoelectric conversion efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photoelectric conversion device, and particularly to the structure of a high-efficiency solar cell.

[Conventional technology]

In order to improve the photoelectric conversion efficiency of the photoelectric conversion device, positive and negative electrodes were provided on the surface where light does not enter, thereby eliminating loss due to absorption of incident light by the electrodes.

There are so-called back-side bonding photoelectric conversion devices, and
The contact area of the interface (contact) between the electrode and semiconductor, where minority carriers generated by incident light are likely to recombine, has been reduced. There is research on the so-called point contact type (
I.E.E., Electron Device Letters, No. ED-6, p. 405, 1985 (R,A,
5intonet al, I E E
E Electron Devices L
etters.

Vol. ED-6, No. 8. (1985) P.
405) and U.S. Pat. No. 4,234.352 (U.S.
See P4.234, 352)).

This solar cell has no electrodes that quickly cut off light or semiconductor regions containing high concentration of impurities on the light incidence side, and these are all formed on the back side opposite to the light incidence side, resulting in high conversion efficiency. , a plan view of the back surface thereof is shown in FIG. 3. Under the finger-shaped electrodes 3 and 4, a dotted N+ or P-decade semiconductor layer is formed, respectively, via an insulating layer (not shown), and the insulating layer The electrode and the semiconductor are in point contact through holes 1 and 2 provided in the electrode.

In this case, since the contact area between the semiconductor and the electrode is small, the amount of minority carriers annihilated at the electrode is reduced, resulting in improved efficiency.

[Problem that the invention seeks to solve]

In the above conventional technology, the electrode contacts that collect minority carriers (electrons in the case of p-type semiconductors, holes in the case of n-type semiconductors) are dot-like and have a small area, so the ability to collect electrons is small and sufficient efficiency is not achieved. There is a possibility that no improvement can be made.

An object of the present invention is to solve the above problems and propose a structure for a solar cell with higher efficiency.

[Means for solving problems]

The above object is achieved by forming one of the contact regions of the semiconductor with the electrode into a finger shape. In particular, the positive electrode contact is made dot-shaped to reduce recombination of electrons, and the negative electrode contact is made finger-shaped to increase the area and improve collection of electrons.

[Effect]

By making the contact area between the electrode and the semiconductor that collects minority carriers finger-shaped to increase the contact area between this and the electrode, a large amount of electrons that reach the electrode via this area flow into the electrode. be able to. Therefore, photoelectric conversion efficiency increases.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a back structure, and FIG. 2 is a sectional view taken along line AA' in FIG. 1.

Oxidizing the surface of the P-type semiconductor layer 11 with a specific resistance of 5 Ω·cm,
Oxide films 9 and 10 are formed on the front and back surfaces. Oxide film 9 on the back side
Form a resist mask using photolithography,
Using this as a mask, finger-shaped grooves for forming the N-type semiconductor region 5 and holes for forming the P-type semiconductor region 6 are created. Furthermore, using the resist mask as a mask, p and BF ions were implanted into each semiconductor region forming hole.
Form N+ and P small regions. Subsequently, a heat treatment is performed at 900° C. for 30 minutes to activate the implanted layer, and the N+ type semiconductor region 5 and the P+ type semiconductor region 6 are completed. Next, using photolithography and vacuum evaporation, each semiconductor region 5 is
and 6 to form a composite finger-shaped electrode of T i /A g. Furthermore, if efficiency is to be improved, a two-layer antireflection film of MgF2/TiO2 or a well-known textured surface is formed on the light incident surface on the back surface, and then an antireflection film 10 such as an oxide film and an antireflection film is formed. do.

〔Effect of the invention〕

According to the present invention, it is possible to provide a structure in which minority carriers are effectively collected and taken into the PN junction region from the bulk semiconductor layer and the series resistance is small.

Therefore, it is possible not only to provide a photoelectric conversion device with high conversion efficiency, but also to contribute to higher performance and smaller size.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining the present invention in detail,
and FIG. 3 are diagrams for explaining the prior art.

Claims (1)

[Claims] 1. A semiconductor substrate has an N^+ layer and a P^+ layer in an interdigital pattern on the surface opposite to the light incident surface (hereinafter referred to as the back surface), and the N^+ layer is formed on the back surface. On either the layer or the P^+ layer, there are point-like holes with an area smaller than the area of the layer, and on the other layer, there are finger-like holes (with an area smaller than the area of the layer). 1. A photoelectric conversion device comprising: an insulating film having an insulating film (a through hole), and interdigital electrodes on the insulating film, which contact the N^+ layer or the P^+ layer through the hole.