Optical properties of CdS thin films obtained by CSVT under different growth conditions and their influence in prototype PV devices

Abstract

We present in this work studies of photoluminescence at room temperature, AFM and optical transmission measurements of Cadmium Sulphide (CdS) films grown by the Closed Space Vapor Transport (CSVT) technique. Normally as-grown CdS-CSVT thin film samples do not show luminescence at room temperature, due mainly to the high density of deep non-radiative recombination centers at the band gap, thus in principle it is logic to think that a change of the critical growth parameters allows us to promote a reduction of the density of defects giving rise to a better quality of CdS-CSVT films, which can show luminescence at room temperature and are also suitable for PV-applications. Morphological changes in the films are also showed by AFM measurements, when we use different kinds of atmospheric molecular species (Ar, N 2 and O 2 /Ar) in the growth chamber. Our PV-devices in the superstrate configuration, using these CdS thin films as windows layer, present also a relative increment in the conversion efficiency, when the pressure in the growth chamber increases. The comparative J-V measurements of the solar cells processed in this work are also illustrated and discussed.