Polyether Polyurethane-based Ionic Liquid Solid Electrolyte For DSSCs

Dye-sensitized solar cell(DSSC)has attracted more attention from researchers because of its high conversion efficiency,low cost of raw materials and simple process operation.Electrolyte,as a key component of the DSSC,bears the role of dye regeneration and electron transport affecting the overall performance of the cell.In this paper,a kind of polyether urethane solid electrolyte with side chain containing ionic liquid structure was studied.It was thought that the charge transport capacity of the solid electrolyte can be improved by introducing ionic groups into the polymer molecular chain.The conductivity of solid electrolyte can be further improved by adding flexible PEG and iodine-containing ionic liquid.In addition,the electrolyte can also be used to assemble DSSC by in situ polymerization.This assembly mode solves the poor contact problems of interface between the solid electrolyte and TiO2 electrode,which is contributed to the DSSC performance.Firstly,a series of imidazoles polyionic liquids(PECHICI)with different molecular weights were synthesized.The results of FTIR and 'H-NMR showed that the preparation product was a polymer with side groups of ionic liquids.Subsequently,the effects of preparation influences,such as different molecular weight of PECHICI,different ratio of PECHICI5000 and PEG10000,different structure of ionic liquid,different proportion of ionic liquid and inorganic salt NaI,on the conductivity of polyurethane ionic liquid solid electrolyte were explored.It was found that the highest conductivity of electrolyte reached 2.42 mS·cm-1 when the ratio of PECHICI5000 and PEG 10000 was 1:1.The results of SEM and DMA showed that the solid electrolyte had a three-dimensional network structure with high elastic modulus.The DSC curves showed that the electrolyte had a good thermal stability in the range of-50??150?.Solid DSSCs were assembled by in situ polymerization based on the four series of electrolytes prepared.The results of photoelectric performance of DSSCs showed that the best efficiency of 4.93%under the light intensity of 100mW·cm-2 was achieved in the cell based on the electrolyte prepared with the ratio 3:1 of PECHICI5000 and PEG10000.The SEM figures and AC impedance spectra of the cross-section of the DSSC showed that the increase of the flexible segment in the solid electrolyte was helpful to improve the wettability between the electrolyte and the TiO2 electrode and reduce the interfacial impedance.The imidazolium ion group on the PECHICI side not only reduced the transmission impedance of the electrolyte,but also improved the open circuit voltage of the DSSC,which improved the cell performance.