Direct solution coating of pure-phase Cu2SnS3 thin films without sulfurization

Abstract

In this paper, we report a solution method to fabricate Cu2SnS3 thin films without involving post sulfurization. The effects of thiourea/metal radios in the precursor solution and the annealing temperatures on the structural, compositional and optical properties of Cu2SnS3 thin films were investigated. The results of X-ray diffraction patterns, Raman spectroscopy and field-emission scanning electron microscopy indicate that the S-rich condition is preferred to suppress the growth of secondary phase Cu4SnS4. Furthermore, to avoid the over evaporation of volatile SnS, a medium annealing temperature was proved critical to obtain phase-pure Cu2SnS3 film. The UV–Vis spectroscopy shows the excellent absorption behavior in the visible light region for Cu2SnS3 prepared at the annealing temperature of 540 °C with the thiourea/metal ratio of 6, which corresponds to a direct band gap of ~1.02 eV.