Thermally evaporated CdTe thin films for solar cell applications: Optimization of physical properties

Abstract Microstructure and other physical properties of CdTe thin films are directly affected by the deposition conditions as well as post deposition treatments. In this respect, CdTe films were fabricated using thermal evaporation technique at different substrate temperatures from 125 to 300 °C and subjected to post deposition air annealing and chemical etching to observe the alterations of structural, optical and electrical properties. Larger crystallite size, lowest strain and dislocation density were observed for the films fabricated at a substrate temperature of 250 °C. Lowest Urbach energy, refractive index, optical conductivity, extinction coefficient and dielectric constants were also found for films deposited under a substrate temperature of 250 °C. Additionally, lower resistivity was observed for the films etched with NP etchant compared to the un-etched films. According to the results, films fabricated at a substrate temperature of 250 °C can be concluded as the best films for potential photovoltaic applications.