Photoluminescence study of Cu2ZnSnS4 thin film solar cells

Cu 2 ZnSnS 4 (CZTS) is considered as a non‐toxic and low‐cost absorber material for solar cells, which has optimum direct bandgap energy for solar energy absorption and high absorption coefficient. In order to achieve higher solar cell efficiencies of CZTS, a better understanding about its defect structure is required. In this study, the defect levels of CZTS are investigated by means of photoluminescence measurements. At temperatures lower than 150 K, a broad emission band around 1.17 eV was observed. The emission band around 1.38 eV was observed at temperatures higher than 125 K. Measurements of PLE spectra for these two emissions have been performed. The emission at 1.17 eV is found to be from the CZTS layer, and its thermal activation energy of 40 ± 9 meV was obtained from the temperature dependence of PL spectra. The emission at 1.38 eV is found to be from the CdS layer.