A poly(styrene-co-acrylonitrile) gel electrolyte for dye-sensitized solar cells with improved photoelectrochemical performance

A polymer gel electrolyte (PGE), using poly(styrene-co-acrylonitrile) (SAN) as a gelator, 1-butyl-3-methylimidazolium iodide (BMIMI) as the ionic liquid, and lithium iodide (LiI) as a source of iodide ions, is synthesized and investigated for its performance while employing it in a quasi-solid-state dye-sensitized solar cell using a N719 sensitizer and an I−/I3− redox couple. The PGEs are synthesized using different wt% of SAN and the relative amounts of LiI and I2 are optimized for iodide ion (I−) and triiodide ion (I3−) generation and their influence on the photovoltaic performance of the devices was investigated. On optimizing the PGE composition, the device gives an ionic conductivity of 7.00 mS cm−1, with a triiodide diffusion coefficient of 7.28 × 10−5 cm2 s−1, ensuring efficient polymer networks for the mobility of ionic species. The absorption edge for all PGEs lies close to ∼420 nm having transparency of more than 80% in the visible and NIR region. Impedance analysis evidently supports 17 wt% SAN as the optimum composition for PGE with better charge transfer and a decrease in recombination rate and considerable improvement in the electron lifetime. The highest photovoltaic conversion efficiency is 6.72% with the 17 wt% SAN PGE.