High efficiency and stability of quasi-solid-state dye-sensitized ZnO solar cells using graphene incorporated soluble polystyrene gel electrolytes

We report on the preparation of highly effective composite electrolytes by combining the two-dimensional graphene (Gra) and soluble polystyrene (PS) nanobeads on Pt counter electrode for the quasi-solid-state electrolytes of ZnO based dye-sensitized solar cells (DSCs). Under an optimized Gra/electrolyte ratio of 12 mg mL(-1), the ionic conductivity (a) of Gra-PS electrolyte was significantly improved from 32.8 mS cm(-1) to 39.8 mS cm(-1). And the electrochemical impedance spectroscopy (EIS) analysis proved that the ZnO-DSC with the optimized composite electrolyte possessed the lowest impedance value. As a result, the overall power conversion efficiencies (PCEs) of quasi-solid-state ZnO-DSCs significantly enhanced to 5.08% from initial 4.09%. Moreover, the results of long-term stability assays showed that the gel-state Gra-PS ZnO-DSC could retain over 90% of its initial PCE after radiation of 1000 h under full sunlight outdoors. It is anticipated that this work may provide an effective way to increase the cell efficiency by the introduction of Gra into gel electrolyte as well as a great potential for practical application. (C) 2014 Elsevier B.V. All rights reserved.