Dependence of photoluminescence on sulfurization temperature of Cu2SnS3 thin films

The dependence of photoluminescence (PL) on sulfurization temperature of the Cu2SnS3 (CTS) thin films was investigated. CTS thin films were prepared at various sulfurization temperatures in the range of 500-600 celcius, and differences in the conversion efficiency of solar cells with the CTS thin films as absorption layer and the crystal structure of the CTS thin films were observed. In low-conversion-efficiency CTS films, which were a mix of monoclinic and cubic crystals, the PL spectrum only showed donor-acceptor pair (DAP) recombination luminescence due to deep defects. In high-conversion-efficiency CTS thin films, which contained only monoclinic crystals, the PL spectrum showed DAP recombination luminescence originating from the same deep defects. In addition band-edge luminescence was observed at room temperature. Thus, it was found that the conversion efficiency and crystal structure of CTS thin film can be easily estimated from PL measurements.