Development of copper sulfide/cadmium sulfide thin film solar cells. First technical progress report, 13 July 1979 to 12 October 1979

Abstract

Preparation of CdS films by evaporation from a single graphite source, as generally used by the Institute of Energy Conversion (IEC) group at the University of Delaware, has been implemented. Previously at Westinghouse, four evaporation sources were used to permit uniform coverage of large area substrates. The graphite source used in this period is somewhat smaller than the IEC design to permit accommodation to the heater geometry currently available. Initial efforts with the single source evaporation have been on characterizing the thickness profiles of the deposited films. This is needed to permit selection of conditions for obtaining films of about 30..mu..m thickness over the central 4 cm x 4 cm area of the substrate. Barrier processing according to the details of IEC method has been used on four-source CdS films. To date the best cells have only been about 1% efficient. Low short circuit current density values (approx. 5 mA/cm/sub 2/) have been the biggest problem. Annealing in 6% H/sub 2//Ar mixtures at 170/sup 0/C after electrode grid evaporation generally has resulted in reduced values of J/sub sc/. Plans for the next period include the use of single source films for cell processing and the use of small area diodemore » arrays to map cell performance parameters as a function of position on the substrate.« less