Sulfurization and annealing effects on thermally evaporated CZTS films

Abstract Thermally evaporated Cu 2 Zn 1.5 Sn 1.2 S 4.4 (CZTS) films are annealed and sulfurized at different temperatures to study the structural modifications. The kesterite phase formation and phase purity of the CZTS films are compared and confirmed by X-ray diffraction and Raman spectroscopic technique. Surface oxidation state of the elements in the sulfurized film is studied by XPS. The calculated optical band gap of the 550 °C sulfurized CZTS film is found to be 1.56 eV; however getting modified due to annealing and sulfurization. The carrier concentration, resistance and mobility of the sulfurized films are found to be 2.8×10 14  cm −3 , 2686 Ω/square and 8.2 cm 2 V −1 s −1 respectively and the conduction type is p-type. This study sheds light on the effect of annealing and sulfurization on various phase-modifications and the light-harvesting capability of CZTS absorber layers for solar cell applications.