Comprehensive study of physical properties of cadmium telluride thin films: effect of post-deposition high annealing temperature

Abstract

Abstract Thin films of cadmium telluride (CdTe) with a thickness of 550 nm were prepared using the thermal evaporation method. The resulting films were annealed in air atmosphere at 200 °C, 300 °C, 400 °C and 500 °C. The annealed films were subjected to x-ray diffraction (XRD), micro-Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), ultraviolet-visible spectroscopy and transverse current–voltage (I–V) test analyses to investigate the structural, surface morphological, optical and electrical properties of films, respectively. The XRD patterns reveal the zinc blende structure of the pristine and treated film with the preferred (111) orientation. In addition, the crystallite size increases with the rise in annealing temperature. The Raman spectra reveal a redshift with annealing as well as the formation of Te precipitates in CdTe films. The SEM images show the uniformity and homogeneity of the as-prepared films. The AFM studies show an increase in the surface roughness of the annealed films. The optical energy band gap is found to decrease with the annealing temperature. The I–V measurement indicates the ohmic behavior of CdTe films. The experimental results indicate that the annealed CdTe thin films at 400 °C have optimized physical properties for solar cell applications as an absorber layer.