This work demonstrates a straightforward strategy to develop the copper-indium-sulfide (CIS) quantum dot-sensitized solar cells (QDSSCs) consisting of ionic liquids (ILs) as electrolyte instead of any volatile solvent. The power conversion efficiency (PCE) of the solar cell yielded with 0.36% in the presence of 1-butyl-3-methylimidazolium sulfide ([BMIm][S2−/Sn 2−]) as electrolyte. Furthermore, binary mixture of [BMIm][S2−/Sn 2−] and 1-butyl-3-methylimidazolium thiocyanate ([BMIm][SCN]) exhibited an improvement of J SC and FF yielding with 0.75% (J SC: 8.69 mA cm−2, V OC: 0.32 V, FF 26.8%). It exhibited long-term stability within 20% drops after 72 h-continuous photo-irradiation and subsequent storage for more than 1300 h in dark. It is due to suppression of the volatilization of solvent and decomposition of sulfide/polysulfide (S2−/Sn 2−) anions. The solar cell performances were found to promote as an increase of interfacial charge transfer efficiency between electrolyte and electrodes by means of electrochemical impedance spectroscopy.