Enhancement of grain growth in Cu₂SnS₃ thin films prepared by the addition of Au and fabrication of solar cells using Au-added CTS thin films

Abstract

Cu2SnS3 (CTS) obtained by depositing Au on an Sn/Cu metal stacked precursor fabricated by electron beam deposition and sulfurization was investigated. In thin films obtained by sulfurization at 560 °C of the precursor with SLG/Mo/Sn/Cu/Au/NaF structures fabricated on Soda lime glass substrates containing alkali metals, a significant increase in the CTS grain size was observed in the Au deposition thickness range of 525 nm. By contrast, no crystal growth was observed in thin films with a precursor without an NaF layer fabricated using alkali-free glass (EAGLE XG), regardless of the thickness of the Au-deposited film. Therefore, appropriate amounts of Au and Na promote the crystal growth of CTS. In addition, at the sulfurization temperature of 570 °C, the crystal grains were larger than those of the thin film fabricated at 560 °C. In the fabricated CTS thin-film solar cells, with sulfurization temperature of 570 °C and Au deposition thickness of 10 nm, open circuit voltage of 0.261 V, short circuit current density of 25.4 mA/cm2, fill factor of 0.425, and power conversion efficiency of 2.82% were obtained.