A new series of electrolytes composed of LiI and acetamide have been investigated in dye-sensitized solar cells (DSSCs). These electrolytes melt at about 50°C and their ionic conductivities vary drastically below and above the melting points (T m). They tend to form large crystals at low temperature, leading to poor penetration and contact within porous TiO2 anode film. This shortage is improved by introducing nano-SiO2 particles into the electrolyte. A total conversion efficiencies (η) of 0.3% at 35°C and 4.2% at 75°C are achieved respectively under AM 1.5 simulated solar light illumination when a LiI/acetamide (1:16) electrolyte with 8wt% nano-SiO2 is used. It is expected that the DSSC using phase transition electrolyte could show high efficiency for operation at high temperature and high stability for storage at low temperature.