The examination of stable charge states of vacancies in Cu2ZnSnS4

TL;DR

This study investigates the stable charge states of vacancies in Cu2ZnSnS4 using hybrid functional calculations, revealing their stable charge states and emphasizing the importance of examining these states prior to charge transition energy level analysis.

Contribution

The paper provides a detailed analysis of stable vacancy charge states in Cu2ZnSnS4 using hybrid functional methods, highlighting their significance for defect level calculations.

Findings

Cu, Zn, and S vacancies have only one stable charge state each.

Sn vacancy has three stable charge states, potentially explaining charge transition levels.

Stable charge state analysis is crucial before calculating charge transition energy levels.

Abstract

The stable charge states of vacancies in the solar cell absorber material Cu2ZnSnS4 are investigated using Kohn-Sham (KS) defect-induced single particle levels analysis by concerning the screened Coulomb hybrid functional. We found out that the Cu, Zn and S vacancies (denoted by VCu, VZn, VS) do not induce single particle defect levels in the vicinity of the band gap thus each of them has only one stable charge state corresponding to the fully occupied valence band VCu1-, VZn2- and VS0, respectively (and therefore cannot account for any defect transition energy levels). The Sn vacancy (VSn) has three stable charge states VSn2-, VSn3- and VSn4-, which may account for two charge transition energy levels. By comparing with previous charge transition energy levels studies, our results indicate that the examination of stable charge states is a necessary and important step which should be done before charge transition energy levels calculations.