Polyvinyl Butyral-Based Thin Film Polymeric Electrolyte for Dye-Sensitized Solar Cell with Long-Term Stability

Polyvinyl butyral (PVB), a polymer used world-wide in laminated glass, has been incorporated into dye-sensitized solar cells (DSSCs) as a quasi-solid polymeric electrolyte (SPE) thin film. SPE thin films soaked with different amounts of liquid electrolyte were prepared. The surface morphologies, the diffusion coefficients, and the ionic conductivities of the SPE thin films were analyzed as a function of the liquid electrolyte content (in weight percent). The optimal ionic conductivity was measured to be approximately 1.1×10^-3 S/cm, which is approximately six orders of magnitude higher than that of the original PVB thin film. The effective resistance of DSSC devices incorporating these thin films was measured using electrochemical impedance spectroscopy (EIS). The EIS spectra show a unique pattern consisting of four semi-circles, which is different from the three-semi-circle pattern observed for DSSCs with a liquid electrolyte. The SPE devices exhibited a high conversion efficiency of 5.46% at 100 mW/cm², approximately 94% that of corresponding liquid-electrolyte cells. The devices' long-term durability was tested to be over 3000 hrs.