Binary ionic liquid electrolytes for copper indium sulfide quantum dot sensitized-TiO2 solar cell to achieve long-term durability

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−/Sn2−]) as electrolyte. Furthermore, binary mixture of [BMIm][S2−/Sn2−] and 1-butyl-3-methylimidazolium thiocyanate ([BMIm][SCN]) exhibited an improvement of JSC and FF yielding with 0.75% (JSC: 8.69 mA cm−2, VOC: 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−/Sn2−) 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. This work demonstrates a straightforward strategy to improve the durability of the copper-indium-sulfide (CIS) quantum dot-sensitized solar cells (QDSSCs) consisting of ionic liquids (ILs) as electrolyte instead of any volatile solvent. The binary of [BMIm][S2−/Sn2−] with [BMIm][SCN] exhibited the PCE yielding with 0.75%, and its stability was maintained within 20% drops after 72 h-continuous photo-irradiation and subsequent storage for more than 1300 h in dark. [Display omitted] •Copper-indium-sulfide quantum dot-sensitized solar cells (QDSSCs) were fabricated.•Imidazolium ionic liquids (ILs) involving S2−/Sn2− ions were employed.•Binary of [BMIm][S2−/Sn2−] with [BMIm][SCN] exhibited high ionic conductivity.•ILs with non-volatilization makes highly stable solar cell performance.