Surface Functionalization of TiO₂ Nanoparticles Influences the Conductivity of Ionic Liquid-Based Composite Electrolytes

As one of the main components of ionic liquid-based composite electrolytes, nanoparticles play a major role in determining the performance of such electrolytes. In this study, four different TiO2-based nanoparticles are introduced into ionic liquid electrolytes to systematically investigate the influence of their conductivities and surface chemistries on the performance of composite electrolytes. Compared with conventional insulating nanoparticles, high-conductivity nanoparticles are free of blocking junctions, and the surface region of the nanoparticles can act as an additional pathway for ionic conduction. Meanwhile, the surface chemistry of the nanoparticle strongly determines the viscosity, network stability, and microscopic morphology of an ionic liquid-based composite electrolyte, thus affecting the ionic conductivity. Therefore, the highest conductivity of 4.29 mS cm–1 is achieved by the ionic liquid-based composite electrolyte with the SC-HC-TiO2 nanoparticle at a weight of 10 wt %, which has high conductivity and rich amino functional groups. DSCs using SC-HC-TiO2 show a high efficiency of 8.12% due to the simultaneous improvement of photocurrent density (Jsc), open-circuit voltage (Voc), and fill factor (FF).