Inhibiting formation of Zn2+/N179 molecules insulation layer and degradation of ZnO-based dye-sensitized solar cells via quasi-solid-state electrolytes

Abstract

ZnO dye-sensitized solar cells (DSSCs) have been deemed as one of promising solar devices. However, ZnO DSSCs with liquid electrolyte always surfer from dissolution of ZnO film and formation of ZnO2+/Ru-based dye molecules insulation layer, thus weakens conversion efficiency and long-tern stability of the devices. To overcome these obstacles, quasi-solid-state iodine-based electrolytes based on PVDF-HFP, and filled with functionalized multi-walled carbon nanotube (FMWCNT) improve its ionic conductivity via increasing charge transport channels and free volume of iodine/tri-iodine. It is found that optimal conversion efficiency of 3.87% was achieved in ZnO nanosheets (NSs) DSSC with 0.5 wt%-FMWCNT quasi-solid-state electrolyte. Namely, it achieves approximate conversion efficiency of the DSSC with typical liquid iodine-based electrolyte (3.94%) under ~ half of ionic conductivity of liquid electrolyte. Moreover, this device remains 86.65% of original conversion efficiency after 1008 h, which is higher than that of the device with liquid electrolyte (50.37%). The result confirms that quasi-solid-state electrolyte inhibits dissolution of ZnO film and formation of ZnO2+/N719 molecules insulation layer.