One-pot hydrothermal synthesis and fabrication of kesterite Cu2ZnSn(S,Se)4 thin films

Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) powder was synthesized by a hydrothermal process. The thin films were fabricated by physical vapor deposition of CZTSSe powder followed by a thermal annealing process. The kesterite microstructure was identified by the X-ray diffraction and Raman spectroscopy. The morphology and elemental composition of CZTSSe thin films were also investigated. The dependence of resistance on the temperature of CZTSSe film was measured and the thermal activation energy of conductivity was estimated to be 0.33 eV based on Arrhenius plot of resistance versus temperature. A high absorption coefficient (> 104 cm−1) of CZTSSe was found in the visible and NIR regions of the spectrum. A direct band gap structure with band gap energy of 1.46 eV was also estimated for CZTSSe films. The photoconductivity was measured under both AM 1.5G and NIR illumination and a stable and fully recoverable photoconductivity was observed for both as-deposited and annealed CZTSSe films. The annealed films show a higher photoconductivity than the as-deposited films under both AM 1.5G and NIR lights.