Structural, optical, and electrical tuning of CZTSe thin films prepared from sintered powder by one-step thermal evaporation

Cu 2 ​ZnSnSe 4 ​ (CZTSe) thin films were deposited by one-step thermal evaporation using a sintered CZTSe powder source, and the effects of post-deposition annealing on their compositional, structural, morphological, optical, and electrical properties were systematically investigated. The results demonstrate that heat treatment significantly influences the structural, morphological, optical, and electrical characteristics of the films. The film annealed at 400 °C exhibited the highest crystalline quality and the strongest formation of the kesterite CZTSe phase, together with a substantial reduction in Cu 2−x Se-related secondary-phase content. AFM analysis revealed progressive surface coarsening with increasing annealing temperature, with pronounced morphological heterogeneity at 500 °C. The optical band gap gradually decreased with increasing annealing temperature, reaching 1.15 eV for the film annealed at 400 °C. Four-point-probe measurements showed that the resistivity increased with annealing temperature and reached its maximum value at 400 °C. The results highlight both the processing simplicity and compositional limitations of single-source thermal evaporation and identify 400 °C as the optimum annealing temperature for enhancing kesterite phase formation and the overall material properties of the CZTSe thin films.