Investigation of Physical Properties of e-Beam Evaporated CdTe Thin Films for Photovoltaic Application

CdTe thin films with 2.8 µm thickness were deposited by electron beam evaporation method. X-ray diffraction, scanning electron microscopy, UV-Vis-NIR spectroscopy and atomic force microscopy (AFM) were used to characterize the films. The results of AFM analysis revealed that the CdTe films have uniform surface. CdTe thin films were heat-treated by SnCl2 solution. Structural analysis using XRD showed that heat treatment by SnCl2 solution improves thin film crystallinity. Three-dimensional AFM images show that CdTe films have grown as nanocone arrays with maximum height of ~21 nm. The average roughness of the film surface on area of 2×2 µm2 is ~2.28 nm. The resultant films are closely packed and has smooth surface which is suitable for photovoltaic applications. A solar cell device was fabricated based on electron beam deposited poly-crystalline CdTe and CdS thin film as absorber and window layer on ITO coated soda lime glass as substrate. The electrical characteristics of CdS/CdTe thin film solar cells were investigated under illumination. From the current-voltage characteristics of fabricated device a typical rectifying photovoltaic behavior was obtained.