Elucidation of electrical properties of undoped and Sb-induced Cu₂SnS₃(CTS) thin films and degradation properties on CTS thin films and solar cells by intentional proton irradiation

The fundamental electrical properties of undoped and Sb-induced Cu2SnS3 (CTS) thin films were evaluated. Furthermore, the relationship between defect properties during intentional degradation and thin film/solar cell properties was investigated. The carrier concentration decreased after Sb induction in the CTS film, and the resistivity increased by one order of magnitude. These values were independent of the Sb volume. These results imply that a small quantity of Sb atoms passivates the defects, such as Sb atoms at Sn or Cu sites that compensate for the intrinsic acceptors at Cu vacancies. In addition, the number of defects around the grain boundary tended to decrease with Sb induction because of passivation. The carrier concentration of the CTS layer remained unchanged following proton irradiation at 1 × 1014 cm-2. Furthermore, the number of defects increased, independent of the Sb induction.