Process for fabricating polycrystalline semiconductor thin-film solar cells, and cells produced thereby
First Claim
1. Method of fabricating a thin-film semiconductor heterojunction photovoltaic device, comprising the steps of:
- a) depositing a layer of cadmium stannate on a transparent substrate by radio frequency sputtering at ambient temperature to act as a transparent conductive oxide (TCO) layer forming a front contact;
b) depositing a zinc stannate layer on said TCO layer by radio frequency sputtering at ambient temperature to form a buffer layer;
c) depositing a first semiconductor window layer upon said buffer layer;
d) depositing a second semiconductor layer upon said window layer to form a heterojunction; and
e) heat treating the device formed by steps (a)-(d) to convert said cadmium stannate layer to a substantially single-phase material with a spinel crystal structure.
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Abstract
A novel, simplified method for fabricating a thin-film semiconductor heterojunction photovoltaic device includes initial steps of depositing a layer of cadmium stannate and a layer of zinc stannate on a transparent substrate, both by radio frequency sputtering at ambient temperature, followed by the depositing of dissimilar layers of semiconductors such as cadmium sulfide and cadmium telluride, and heat treatment to convert the cadmium stannate to a substantially single-phase material of a spinel crystal structure. Preferably, the cadmium sulfide layer is also deposited by radio frequency sputtering at ambient temperature, and the cadmium telluride layer is deposited by close space sublimation at an elevated temperature effective to convert the amorphous cadmium stannate to the polycrystalline cadmium stannate with single-phase spinel structure.
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Citations
18 Claims
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1. Method of fabricating a thin-film semiconductor heterojunction photovoltaic device, comprising the steps of:
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a) depositing a layer of cadmium stannate on a transparent substrate by radio frequency sputtering at ambient temperature to act as a transparent conductive oxide (TCO) layer forming a front contact; b) depositing a zinc stannate layer on said TCO layer by radio frequency sputtering at ambient temperature to form a buffer layer; c) depositing a first semiconductor window layer upon said buffer layer; d) depositing a second semiconductor layer upon said window layer to form a heterojunction; and e) heat treating the device formed by steps (a)-(d) to convert said cadmium stannate layer to a substantially single-phase material with a spinel crystal structure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 18)
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14. A method of fabricating a thin-film CdS/CdTe heterojunction photovoltaic device, comprising the steps of:
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a) depositing a layer of cadmium stannate on a transparent substrate by radio frequency sputtering at ambient temperature to act as a TCO layer forming a front contact; b) depositing a zinc stannate layer on said TCO layer by radio frequency sputtering at ambient temperature to form a buffer layer; c) depositing a cadmium sulfide window layer upon said buffer layer by radio frequency splattering at ambient temperature; and d) depositing a layer of cadmium telluride upon said window layer by close space sublimination at elevated temperature, thus forming a heterojunction, wherein the temperature profile for the close space sublimation of said cadmium telluride is effective to convert said cadmium stannate layer to a substantially single-phase material with a spinel crystal structure. - View Dependent Claims (15, 16, 17)
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Specification