Effect of CdCl2 annealing treatment on structural and optoelectronic properties of close spaced sublimation CdTe/CdS thin film solar cells vs deposition conditions

CdTe/CdS thin films were deposited by close-spaced vacuum sublimation at substrate temperatures 250-500 °C. The effect of substrate temperature in conjunction with CdCl2 heat treatment on the properties of CdTe/CdS thin films and devices is reported. X-ray diffraction measurements of structural properties of the films were carried out to study their phase composition and texture. Surface morphology, grain size and growth mechanism of the films were determined by the scanning electron microscopy. The photoluminescence measurements allowed us to establish the correlation between the point and extended defect structure on the one hand and the growth conditions on the other. The CdTe/CdS solar cells fabricated at high substrate temperature, exhibited improved electrical characteristics compared to cells fabricated at low substrate temperature, yielding a high efficiency.