Thermally evaporated CdS/CdTe thin film solar cells: Optimization of CdCl2 evaporation treatment on absorber layer

Abstract

CdCl2 treatment is crucial in the fabrication of highly efficient CdS/CdTe thin-film solar cells. This study reports a comprehensive analysis of thermal evaporated CdS/CdTe thin-film solar cells when the CdTe absorber layer is CdCl2 annealed at temperatures from 340 to 440 ◦C. Samples were characterized for structural, optical, morphological and electrical properties. The films annealed at 400 ◦C showed better crystallinity with a cubic zinc blende structure having large grains. Higher refractive index, optical conductivity, and absorption coefficient were recorded for the CdTe films annealed at 400 ◦C with CdCl2. Optimum photoactive properties for CdS/ CdTe thin-film solar cells were also obtained when samples were annealed at 400 ◦C for 20 min with CdCl2, and the best device exhibited VOC of 668.4 mV, JSC of 13.6 mA cm􀀀 2, FF of 53.9% and an efficiency of 4.9%.