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 diode …

Initial studies of p-n heterojunctions formed between undoped trans-(CH)/sub x/ and n-CdS are reported. The junctions were characterized by measurements of current vs voltage (I-V), capacitance vs voltage (C-V), and photovoltaic response spectra. The results are analyzed in terms of the standard heterojunction equations. It is concluded that undoped as-grown films of trans-(CH)/sub x/ are p-type with a residual acceptor concentration of 2 x 10/sup 18/ cm/sup -3/, and that in spite of the complex fibril morphology the semiconductor properties can be inferred by treating (CH)/sub x/ as an effective homogeneous medium. Detailed studies of the photovoltaic response at energies below the energy gap for (CH)/sub x/ imply the existence of a well-defined deep trapping state in polyacetylene with an energy near the center of the gap.