Hydrogen sulphate-based ionic liquid-assisted electro-polymerization of PEDOT catalyst material for high-efficiency photoelectrochemical solar cells.

This work reports the facile, one-step electro-polymerization synthesis of poly (3,4-ethylenedioxythiophene) (PEDOT) using a 1-ethyl-3-methylimidazolium hydrogen sulphate (EMIMHSO4) ionic liquid (IL) and, for the first time its utilization as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). Using the IL doped PEDOT as CE, we effectively improve the solar cell efficiency to as high as 8.52%, the highest efficiency reported in 150 mC/cm2 charge capacity, an improvement of ~52% over the control device using the bare PEDOT CE (5.63%). Besides exhibiting good electrocatalytic stability, the highest efficiency reported for the PEDOT CE-based DSSCs using hydrogen sulphate [HSO4]- anion based ILs is also higher than platinum-(Pt)-based reference cells (7.87%). This outstanding performance is attributed to the enhanced charge mobility, reduced contact resistance, improved catalytic stability, smoother surface and well-adhesion. Our experimental analyses reveal that the [HSO4]- anion group of the IL bonds to the PEDOT, leading to higher electron mobility to balance the charge transport at the cathode, a better adhesion for high quality growth PEDOT CE on the substrates and superior catalytic stability. Consequently, the EMIMHSO4-doped PEDOT can successfully act as an excellent alternative green catalyst material, replacing expensive Pt catalysts, to improve performance of DSSCs.