Optical and Photoelectrical Properties of (CdTe)100-x(SbS)x thin films

The present work deals with the effect of the addition of SbS at the expense of CdTe content on the optical, electrical and photo electrical properties of polycrystalline (CdTe)(100-x)(SbS)(x) (0 <= x <= 28 at.%) thin films. Increasing the SbS content is found to affect the dispersion parameters and energy gap of the films. The transmission spectra, T(lambda), of the films at normal incidence were obtained in the spectral region (400-2500 nm). A straightforward analysis proposed by Swanepoel has been applied to derive the complex index of refraction (real and imaginary parts) and the film thickness with high accuracy. The optical absorption mechanism in the films under study obeys the allowed direct transitions. The optical band gap of (CdTe)(100-x)(SbS)(x) films are decreased from 1.58 to 1.33 eV with increasing SbS content from 0 to 28 at.%. Both of Wemple-DiDomenico and Solomon dispersion relationships were used to obtain the dispersion parameters of the films. The composition dependence of steady state dark and photo conductivities at room temperature shows that the dark and the photo conductivities increase while the activation energies for dark and photoconduction decrease with increasing the SbS content.