Browse Prior Art Database

Polycrystalline Semiconductor Solar Cell

IP.com Disclosure Number: IPCOM000082715D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 32K

Publishing Venue

IBM

Related People

Cuomo, J: AUTHOR [+3]

Abstract

Techniques are described herein for the fabrication of solar cells from polycrystalline films of semiconducting material.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Polycrystalline Semiconductor Solar Cell

Techniques are described herein for the fabrication of solar cells from polycrystalline films of semiconducting material.

The techniques involved include fabrication of the polycrystalline film in a way such that each grain extends through the thickness of the film to form a columnar structure. This is typically done by depositing the film onto a heated substrate. Examples of columnar growth include ZnO or CdS sputtered onto a substrate held at a temperature of about 300 degrees C. Columnar thin films can also be formed in any of the III-V compounds. The grain surfaces and boundaries are doped in a way such that minority carriers are repelled away from the grain boundary region.

The resulting structure is effectively a collection of several isolated single- crystal devices which are connected in parallel. The minority carrier lifetime is kept high by the electric field near the grain boundaries, which keeps these carriers away from the large number of recombination centers in the boundary region. Thus, each grain operates as a single-crystal device.

A junction can be produced by any of several techniques: ion implantation into the top surface; diffusion of a dopant from the substrate into the bottom surface of each grain; the growth of material of one doping type onto grains of another doping type; or the formation of a Schottky barrier at one of the film surfaces. In each case, the effect is to produce a junction parallel to the film surface.

To dope the grain boundary, a majority type dopant is diffused into the film at very low temperature at which grain boundary diffusion is dominant. The...