The effect of different Cu/Sn ratios on the properties of monoclinic Cu2SnS3 thin films and solar cells fabricated by the sol–gel method

Ternary Cu 2 SnS 3 (CTS) is a promising material for thin-film solar cells because it consists of nontoxic and earth-abundant elements. The present paper reports the preparation of monoclinic CTS thin films by a sol–gel solution-based method. The effects of the Cu/Sn atomic ratio on the structure and morphology were investigated. As the atomic ratio of Cu/Sn varied from 1.6 to 2.0, the compactness of the CTS films improved; furthermore, secondary phases, such as SnS, gradually disappeared; and the grain size of the films decreased. The CTS film with a Cu/Sn ratio of 1.9 showed a monoclinic structure with homogeneous morphology and a band gap of 1.12 eV, yielding a power conversion efficiency of 0.58%. These results could pave the way for the development of CTS thin-film solar cells.