Mono-ion transport electrolyte based on ionic liquid polymer for all-solid-state dye-sensitized solar cells

Ionic liquid polymers, poly(1-alkyl-3-(acryloyloxy)hexylimidazolium iodide), are synthesized and used as mono-ion transport electrolytes for all-solid-state dye-sensitized solar cells. For these ionic liquid polymers, imidazolium cations are tethered on polymer main chain and only iodide species is mobile. Such a mono-ion transport feature is favorable as solid-state electrolyte in dye-sensitized solar cells. High thermal stability up to 200 °C for these ionic liquid polymers is confirmed by thermogravimetric analysis. Among these ionic liquid polymers, poly(1-ethyl-3-(acryloyloxy)hexylimidazolium iodide) (PEI) exhibits the highest ionic conductivity (3.63 × 10−4 S cm−1) at room temperature. The dye-sensitized solar cell based on PEI electrolyte without the addition of iodine exhibits the open-circuit voltage of 838 mV, the short-circuit current density of 9.75 mA cm−2 and the conversion efficiency of 5.29%, measured at AM 1.5 illumination (100 mW cm−2). Incorporating iodine into PEI electrolyte results in the decrease of both the open-circuit voltage and the photocurrent density due to the visible light adsorption by iodine and the enhancement of the recombination between conduction band electrons and the triiodide.