Properties of Cu₂ZnSnS₄ films obtained by sulfurization under different sulfur-vapor pressures in a sealed ambient

Thin-films of Cu₂ZnSnS₄ (CZTS), a promising photoabsorber for photovoltaics, were obtained by sulfurization of the precursor films at 550 °C in evacuated and sealed quartz ampoules under various partial pressures (22.3–232.5 kPa) of sulfur-vapor, and its effects on the morphological and optical properties were studied. The precursor films were obtained on the molybdenum (Mo) coated soda-lime glass substrate via solution-chemistry. The observed changes in the morphology have been explained based on the amount of CuS formed and its conversion to sulfur-poor Cu₂S. A decrease in the grain size from 448 to 223 nm was observed with the increase in partial pressure of sulfur-vapor. The thickness of the molybdenum sulfide (MoS₂) layer that forms at the CZTS – Mo interface during sulfurization, increased from 62 to 479 nm. The structural disorder, estimated using Raman spectroscopy, increased with the increase in the partial pressure of sulfur-vapor.