The sunlight is the largest single available source of clean and renewable energy to ensure human society's sustainable development. Owing to their low production cost and high energy conversion efficiency, dye-sensitized solar cells (DSSCs) have been regarded as good alternatives to conventional photovoltaic devices. Herein, a series of composite electrolytes based on poly(ethylene oxide) (PEO) and the binary ionic liquids 1-propyl-3-methy-imidazolium iodide ([PMIm]I) and 1-ethyl-3-methylimidazolium thiocyanate ([EMIm][SCN]) were prepared and then applied to fabricate six DSSCs. The composite electrolytes were characterized by fourier transform infrared spectroscopy (FTIS), X-ray diffraction (XRD), and electrochemical impedance spectra (EIS). It was shown that the addition of binary ionic liquids would reduce the degree of crystallinity of PEO, thus improving the ionic conductivities of the electrolytes by about 2 orders of magnitude. Investigation on the photovoltaic performances of these DSSCs showed that the fill factor (FF) could reach up to 0.67 and energy conversion efficiency (η) could reach up to 4.04% under AM 1.5 full sunlight (100 mW/cm2).
