Effect of substituents in the imidazolium ring on the performance of solid-state dye-sensitized solar cells

Three solid-state imidazolium iodides have been designed and synthesized for use as all-solid-state electrolytes in solid-state dye-sensitized solar cells (ssDSSCs). The effect of substituents in the imidazolium ring on the ionic conductivity and solar cell performance of ssDSSCs has been investigated. As compared to the methyl-ethyl-substituted imidazolium iodide, replacement of one alkyl group (the methyl group) with an ester group increases the ionic conductivity and solar cell performance significantly, and further replacement of the other alkyl group (the ethyl group) with a hydroxyethyl group further increases the ionic conductivity and solar cell performance significantly. A power conversion efficiency of 7.45% has been achieved under the irradiation of simulated AM1.5G solar light (100 mW cm^-2) with the ssDSSC using the hydroxyethyl and ester co-functionalized imidazolium iodide based solid-state electrolyte and a metal-free organic dye sensitizer.