Characterization of Cu2ZnSnS4 Thin Films Formed by Flash Evaporation PVD

In the present work Cu2ZnSnS4 semiconducting thin films were synthesized by deposition of Cu-Zn-Sn alloy films on glass substrate using flash evaporation PVD followed by annealing the films in sulfur containing atmosphere. The influence of process parameters on chemistry, structure, morphology and optical absorption of as-deposited and annealed films was investigated by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy, and UV-visible spectroscopy. Xray diffraction and Raman spectroscopy results showed that the annealed films were mainly composed of Kesterite CZTS. However, UV-visible spectroscopy results revealed that secondary phases affect the optical behavior of the films. In order to reach the optimum properties it is necessary to properly select the process parameters such as PVD source powder composition, sulfur content, temperature and duration of sulfurization. Due to the complex effect of these parameters on structure and properties of the films, the Taguchi design of experiment method was utilized to determine to what extend each parameter is important as well as to predict the best combination of process variables to achieve the optimal bandgap in CZTS thin films. The sample prepared according to the variables suggested by the Taguchi method showed the smallest optical bandgap of 1.56 eV.