Mechanosynthesis, deposition and characterization of CZTS and CZTSe materials for solar cell applications

Abstract

Mechanosynthesis of nanocrystalline powders of CZTS and CZTSe by ball milling technique and the physical properties of thermally evaporated CZTS and CZTSe thin films as a function of substrate temperature are investigated. Nanocrystalline Cu–Zn–Tin–Sulphide (CZTS) and Cu–Zn–Tin–Selenide (CZTSe) powders synthesized by ball milling at different milling time using the source materials of Cu, Zn, Sn, S (or) Se in the ratio 2:1:1:4 are investigated. The above synthesized powder was thermally evaporated on glass substrate kept at room temperature and 673K under a vacuum of 10−6mbar to prepare quaternary compound semiconducting thin films in a single step process. The synthesized powder and deposited CZTS and CZTSe thin films belong to tetragonal crystal system. Raman spectra reveal that the synthesized nanocrystals are pure without any secondary phases. A gradual reduction in optical bandgap of films was observed with increasing substrate temperature due to increased crystallinity of the films. The changes in surface morphology of the films with respect to substrate temperature were studied by scanning electron microscopy and atomic force microscopy. Electrical studies indicate that the deposited films have p-type conductivity.