Environmental effects on the ionic conductivity of poly(methyl methacrylate) (PMMA)-based quasi-solid-state electrolyte

Quasi-solid-state dye-sensitized solar cells (QS-DSSCs) using polymer electrolytes display excellent long-term stability with comparable light to electricity conversion efficiency (PCE). In this paper, poly(methyl methacrylate) (PMMA) is chosen as the template polymer, and polymer viscosity and its weight percentage of PMMA in the I-3 (-)/I- electrolyte system are optimized considering the competitive factors of the ionic conductivity (sigma) and gel dimension stability. A systematic study is carried out to study the environmental factors on the ionic conductivity of quasi-solid electrolytes in terms of storage time, thermal stress, and light soaking. In the different temperature range, the polymer presents different aggregation states and molecular motion forms, which results in different conductive mechanism of the gel electrolyte. It could be described by the Arrhenius equation in the sol state and the Vogel-Tammann-Fulcher (VFT) equation on the gel state, respectively. Both the cyclic voltammetry curve and the Tafel polarization curve indicate that the quasi-solid electrolyte exhibits a lower ion diffusion and transport capacity (1.83 x 10(-6) cm(2)/s) than that of the liquid electrolyte (9.15 x 10(-6) cm(2)/s). This work provides new insights about the degradation mechanism of polymer electrolytes for QS-DSSC application.