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The charge recombination at the TiO2 photoelectrode/electrolyte interface plays a crucial role in determining the efficiency of solid-state dye-sensitized solar cells (DSSCs) because of the poor interface contact at the TiO2 photoelectrode/electrolyte interface. In this work, we report the surface co-grafting of surfactants onto the surface of the TiO2 photoelectrode, and their effects on the photovoltaic performance of solid-state DSSCs. Three ionic surfactants, including anionic surfactants, sodium 2-ethylhexyl sulfosuccinate (AOT) and chenodeoxycholic acid (CDCA), and a cationic surfactant, dodecyltrimethylammonium bromide (DTAB), were applied for the modification of the TiO2 photoelectrode/electrolyte interface. The results show that co-grafting of surfactants AOT or CDCA on the TiO2 photoelectrode surface, and post heat treatment (above the melting point of solid-state electrolytes) could drastically improve the interfacial contact properties of the TiO2 photoelectrode/electrolyte interface, increase the penetration of the electrolytes into the porous TiO2 photoelectrode, and thus enhance the photovoltaic performances of the solid-state electrolyte DSSCs. With the surface modification of AOT/N719, the succinonitrile based solid-state DSSCs exhibited superior long-term stability, and showed power conversion efficiencies of 6.75% and 7.92% under 1.5 solar spectrum illuminations at 100 and 50 mW cm−2, respectively.

A new family of organic ionic plastic crystals (OIPCs) based on bis-quaternary ammonium cations was synthesized and characterized. The synthesized bis-quaternary ammonium salts with bis(trifluoromethanesulfonyl) imide (TFSI−) anions exhibit plastic crystal properties as determined by differential scanning calorimetry (DSC). The high ionic conductivity of the compounds in the solid-state indicated that this new family of OIPCs can be promising solid-state electrolytes for electrochemical devices. Cyclic voltammetry characterization of OIPCs in the liquid-state revealed their wide electrochemical windows and highly reversible lithium metal electrodeposition properties.