THIN-FILMS OF CDTE PRODUCED USING STACKED ELEMENTAL LAYER PROCESSING FOR USE IN CDTE CDS SOLAR-CELLS

The stacked elemental layer (SEL) technique has been used to synthesize thin films of CdTe. This technique consists of depositing alternate layers of Cd and Te in the stoichiometric ratio needed to form CdTe and then annealing the stack to react the layers to form the compound. The Cd and Te layers were deposited using thermal evaporation and annealed in N2, vacuum or air to synthesize the CdTe. Transmittance and reflectance data, X-ray diffraction data and scanning electron microscopy observations of the surface topology are given for the layers produced. Post-synthesis annealing of the layers using CuCl2/CdCl2/methanol was also investigated. Such annealing was found to substantially increase the grain size of the layers produced. The CdS/CdTe solar cells produced using the large grain CdTe have open circuit voltages up to 0.68 V and short circuit currents greater than 11 mA cm-2 under AM0 illumination. A preliminary energy analysis has been carried out, and energy payback times and energy ratios are presented in conjunction with a discussion of the environmental costs of using such technology. The SEL technique promises to be a commercially realizable process for manufacturing CdS/CdTe solar cells.