A hybrid functional study of native point defects in Cu₂SnS₃: Implications for reducing carrier recombination

The native point defects in the earth-abundant solar material Cu₂SnS₃ are studied using the hybrid functional. To generate more accurate formation energies of defects, the extended Freysoldt, Neugebauer, and Van de Walle (FNV) method is used for finite-size corrections in the charged supercell calculations. According to the calculated defect energetics, it is found that the usual experimental conditions can lead to abundant deep centers that deteriorate solar cell performance. To reduce the carrier recombination caused by the deep centers, Sn-rich and S-poor conditions should be attempted. The present calculations also give satisfactory explanations for a recent experimental work on the defect levels in Cu₂SnS₃.