Polymer Electrolytes For Solid-state Dye-sensitized Solar Cells And Their Photoelectrochemical Mechanism

Dye-sensitized solar cells(DSSCs) have received wide academic attention as a kind ofphotovoltaic device with low cost and easy fabrication.By virtue of non-volatility, easypackage and long-term stability, solid-state polymer electrolyte has become one of thesignificant research areas in DSSCs.In this study, a comb-like copolymer poly(N-propyl-vinylimidazoliumiodide-co-poly(ethylene glycol) methyl ether methacrylate) (poly(VImI-co-PEGMA)) wassynthesized. Quasi-solid state DSSCs were fabricated using the copolymer gel as theelectrolyte. Results show that chain segments with the imidazolium cations decrease electronrecombination at the TiO2/electrolyte interface effectively. Moreover, the copolymer not onlygives rise to the upward movements of the conduction band edge of TiO2, but also increasesthe transport resistance of TiO2film. Quasi-solid state DSSCs have obtained an energyconversion efficiency of 4.10% given that the weight fraction of the copolymer is 50% andthe mole ratio VImI to PEGMA is 5.0. In addition, all-solid-state DSSCs, prepared by usingthe copolymer/ PEO blend electrolyte, have received an energy conversion efficiency of3.46%.The WAX and DSC meseasurments indicate that the copolymer can decrease thecrystallinity of PEO and improve the ionic conductivity.All-solid-state DSSCs based on PEO /PEG blend electrolyte were assembled with theaddition of DMAP. Experiments were conducted for investgating the action mechanismbetween DMAP and TiO2surface. It is shown that DMAP significantly improve theopen-circuit voltage of DSSCs, owing to the interaction of DMAP and I3-/I-as well as themodification of the surface distribution of TiO2conduction band, through the analyses ofimpedance and photoelectrochemistry. The high open-circuit voltage of 0.85V is achieved,and the conversion efficiency reaches 4.07%.