Organic ionic plastic crystal, 1-propyl-1-methylpyrrolidinium iodide (P13I), which possesses a broad plastic phase from −36 to 135 °C, was doped with silica nanoparticles (SiO2 NPs) and 1-ethyl-3-methylimidazolium iodide (EMII), for the preparation of SiO2/EMII/P13I solid-state electrolytes for dye-sensitized solar cells (DSSCs). The thermal properties of all the electrolytes, including solid–solid phase transitions and melting temperatures, were investigated by differential scanning calorimetry (DSC). The effect of silica particles on the ionic conductivity, diffusion of I–/I3– redox couple in electrolytes, and photovoltaic performance for solid-state DSSCs were investigated. The fabricated solid-state DSSCs yielded a high power conversion efficiency of 5.25% under simulated air mass 1.5 solar spectrum illuminations at 50 mW cm–2. Furthermore, the DSSCs based on SiO2/EMII/P13I solid-state electrolytes show good stability after an accelerating aging test, demonstrating potential practical applications.Keywords: dye-sensitized solar cells; plastic ionic crystals; SiO2 nanoparticles; solid-state electrolyte; stability;