Cu2SnS3 thin films were prepared by crystallization in a sulfur/tin mixing atmosphere from stacked NaF/Cu/Sn precursors deposited by the sequential evaporation of Sn, Cu elements, and NaF. The NaF mole ratio was changed at (x = 0 to 0.12). From X-ray diffraction patterns and Raman spectra, the Cu2SnS3 thin films were considered to have a monoclinic structure. The grain size of the Cu2SnS3 thin films decreased with increasing NaF/Cu mole ratio. The band-gap energies of the Cu2SnS3 thin films determined from quantum efficiency spectra were 0.93 and 1.02 eV. The solar cell with x = 0.075 demonstrated the best performance, namely, Voc = 283 mV, Isc = 37.3 mA/cm2, FF = 0.439, and η = 4.63%.

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Cu2SnS3 thin films were prepared by crystallization in sulfur and tin mixing atmosphere from the stacked Cu/Sn precursors deposited by sequential evaporation of Sn and Cu elements. From EPMA analysis, the composition of the thin film was approximately constant regardless changing Sn mole ratio in the precursor. However, the composition of inside of the thin films and Mo layer had gradation. The Raman analysis showed that the spectrum corresponded to monoclinic Cu2SnS3. Cu2SnS3 thin films were applied to the fabrication of Cu2SnS3 solar cells. The values of Voc and Isc increased with decreasing Sn mole ratio in the precursor. The largest Voc of 247.5 mV was achieved in sample of Cu/Sn mole ratio of 2/1.2, which is comparable with early reported value of Voc. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)