Radiant energy converter having sputtered CdSiAs.sub.2 absorber
OwnerLubna R. Ijaz, Larry C. Burtoninventors
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Abstract
Thin film radiant energy converter having a sputtered CdSiAs.sub.2 photovoltaic absorber layer and a thermally evaporated CdS top layer. The sputtering technique with multiple targets (Cd, Si, As) is used to obtain stoichiometric CdSiAs.sub.2 thin films which are polycrystalline and have large grain size to thereby reduce grain boundary recombinations of the photogenerated electrons.
Claims13
In the manufacture of a radiant energy conversion cell the improvement comprising,
- forming a polycrystalline layer with large grain size by stoichiometrically sputtering CdSiAs.sub.2 on a substrate using separate targets respectively comprising Cd, Si, and CdAs.sub.2, each said target having an ambient temperature of about 90.degree. C. to about 100.degree. C. with sputter bias voltages between about 0 to 1000 volts, said substrate having a closely controlled ambient temperature, the power for sputtering and temperature being limited to avoid evaporation of arsenic.
In a radiant energy converter including a thin film absorber layer formed as a p-type semiconductor material and a thin film collector layer of an n-type semiconductor material in contact with and forming a heterojunction with said absorber layer, and electrode means on the non-contacting surfaces of said layers, the improvement wherein said absorber layer is a polycrystalline material formed by a controlled sputtering process to have large grain size to reduce grain boundary recombinations of photogenerated electrons and wherein said absorber is stoichiometric CdSiAs.sub.2.
A thin film radiant energy conversion device comprising,
- (a) a conductive substrate,
- (b) a polycrystalline layer of CdSiAs.sub.2, having one surface conductively contacting the surface of said conductive substrate and constituting a p-type semiconductor layer,
- (c) a CdS layer constituting an n-type semiconductor formed in situ on the other surface of said polycrystalline layer,
- (d) a radiant energy transparent conducting layer conductively secured to said CdS layer, and
- (e) output conductor means connected to said conductive substrate and said radiant energy transparent conducting layer.
A method of making a thin film CdSiAs.sub.2 -CdS solar cell comprising,
- (a) forming a conductive substrate,
- (b) forming a polycrystalline layer with large grain size by stoichiometrically sputtering CdSiAs.sub.2 on said substrate, using separate targets respectively comprising Cd, Si, and CdAs.sub.2, each said target having an ambient temperature of about 90.degree. C. to about 100.degree. C., said substrate having an ambient temperature of about 225.degree. C..+-.5.degree. C., with sputter bias voltages between about 0 to about 1000 volts,
- (c) in situ forming said CdS layer on the surface of said CdSiAs.sub.2 layer, and
- (d) applying an electrode to the said CdS layer.
Dependencies are inferred from the claim text.