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Cadmium-free junction fabrication process for CuInSe.sub.2 thin film solar cells

United States Patent

5,948,176
September 7, 1999
View the Complete Patent at the US Patent & Trademark Office
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The present invention provides an economical, simple, dry and controllable semiconductor layer junction forming process to make cadmium free high efficiency photovoltaic cells having a first layer comprised primarily of copper indium diselenide having a thin doped copper indium diselenide n-type region, generated by thermal diffusion with a group II(b) element such as zinc, and a halide, such as chlorine, and a second layer comprised of a conventional zinc oxide bilayer. A photovoltaic device according the present invention includes a first thin film layer of semiconductor material formed primarily from copper indium diselenide. Doping of the copper indium diselenide with zinc chloride is accomplished using either a zinc chloride solution or a solid zinc chloride material. Thermal diffusion of zinc chloride into the copper indium diselenide upper region creates the thin n-type copper indium diselenide surface. A second thin film layer of semiconductor material comprising zinc oxide is then applied in two layers. The first layer comprises a thin layer of high resistivity zinc oxide. The second relatively thick layer of zinc oxide is doped to exhibit low resistivity.
Ramanathan; Kannan V. (Lakewood, CA), Contreras; Miguel A. (Golden, CA), Bhattacharya; Raghu N. (Littleton, CA), Keane; James (Lakewood, CA), Noufi; Rommel (Golden, CA)
Midwest Research Institute (Kansas City, MO)
08/ 939,844
September 29, 1997
CONTRACTUAL ORIGIN OF THE INVENTION The United States Government has rights in this invention pursuant to Contract No. DEAC36-83CH10093 between the United States Department of Energy and the Midwest Research Institute.