Defect chemistry and chalcogen diffusion in thin-film Cu_2ZnSnSe_4 materials

摘要

Selenium diffusion in polycrystalline thin-film Cu_2ZnSn(S,Se)_4 (CZTSe) on molybdenum-coated soda-lime glass substrates was investigated by in situ monitoring of the molybdenum back-contact resistance during high-temperature selenization treatments. In these measurements, selenium diffusion through the CZTSe layer results in conversion of the molybdenum layer to MoSe_2, increasing the sheet resistance of the film stack. By monitoring the rate of MoSe_2 formation as a function of annealing temperature, an activation energy of 0.5 ± 0.1 eV has been measured for selenium diffusion in CZTSe. The partial pressure dependence of chalcogen diffusion suggests that chalcogen vacancies are not the defect controlling chalcogen diffusion in thin-film CZTSe.