Fabrication of Cu₂SnS₃ thin films by sulfurization of evaporated Cu‐Sn precursors for solar cells

Abstract The ternary compound semiconductor Cu 2 SnS 3 (CTS) is formed from non‐toxic materials that are abundant in Earth's crust and other low‐cost elements. CTS has also been reported to a band gap energy range of 0.93–1.77 eV and an absorption coefficient of 1.0×10 4 cm –1 . Consequently, CTS is a potential material for the p‐type absorber layer of thin film solar cells. In this study, we examined the dependence of the optical, electrical and photovoltaic properties of CTS thin films on the Cu/Sn composition ratio. CTS thin films were fabricated by sulfurizing evaporated Cu‐Sn precursors with different Cu/Sn composition ratios at 560 °C for 2 h in a N 2 atmosphere and sulfur vapor. The Cu/Sn composition ratios of the sulfurized films were determined to be 1.6–2.5 by X‐ray fluorescence. The solar cell comprising a CTS thin film with a Cu/Sn composition ratio of 1.77 exhibited the best performance among the cells examined, an open‐circuit voltage of 242 mV, a short‐circuit current density of 28.9 mA/cm 2 , a fill factor of 41.7% and a conversion efficiency of 2.92% were obtained. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)