Effect of Rb addition on Cu₂SnS₃ thin-film solar cells

Abstract Copper tin sulfide (Cu 2 SnS 3 , CTS) thin films were fabricated by depositing RbF via thermal evaporation onto Cu/Sn precursors prepared via electron-beam evaporation, followed by sulfurization of the RbF/Cu/Sn precursors inside a quartz ampoule. The amount of deposited RbF varied between 0 and 100 mg. Thin-film evaluation through Raman spectroscopy revealed that Rb addition promoted the formation of single-phase monoclinic CTS, whereas surface scanning electron microscopy images showed an increase in grain size. Furthermore, a solar-cell performance evaluation indicated increases in the short-circuit current density ( J sc), open-circuit voltage ( V oc), fill factor (FF), and power-conversion efficiency (PCE) with the addition of Rb. Notably, a PCE of 3.91% was achieved when 80 mg of RbF was deposited.