Sulfurization and annealing effects on thermally evaporated CZTS films

Thermally evaporated Cu2Zn1.5Sn1.2S4.4 (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 2.8×1014 cm−3, 2686 Ω/square and 8.2 cm2V−1s−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.