Optical, morphological and electrical studies of thermally vacuum evaporated CdTe thin films for photovoltaic applications

Abstract

Cadmium telluride (CdTe) semiconductor thin films were obtained by thermal vacuum evaporation (TVE) on optical glass substrates. The optical characterizations of CdTe thin films were made by spectroscopic ellipsometry (SE) and optical spectrophotometry. The optical constants (refractive indices and extinction coefficients) were obtained for CdTe thin films of different thicknesses. High absorption coefficients of order 105cm−1 and suitable optical bandgaps values of 1.5eV were obtained. The surface morphology of the obtained films was investigated by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) techniques. The influences of post-deposition thermal treatment on CdTe morphological properties were discussed. The current–voltage characteristics of CdTe films were recorded at temperatures in the range 150–280K. An electrical analysis of the conduction mechanisms specific for different voltage ranges was also employed.