Dye solar cells combining a TiO2 surface-blocking organic sensitizer and solvent-free ionic liquid-based redox electrolyte

Abstract

A surface-blocking triphenylamine-based organic dye (named as D35) is utilized for the fabrication of efficient dye solar cells (DSCs) employing solvent-free ionic liquid electrolytes. The prepared DSCs present power conversion efficiencies of 5.2% under 1 sun AM 1.5G illumination conditions, a performance very similar to solar cells using a reference electrolyte with identical amount (0.2 M) of iodine dissolved in a standard acetonitrile–valeronitrile solvent mixture. Despite the high concentration of recombining species inside the electrolyte, the IL-based cells are able to afford a photopotential (V_oc) of 0.76 V. Electrochemical Impedance Spectroscopy (EIS) has explored the recombination dynamics and conduction band edge shifts, proving the role of the dye's molecular structure on attaining such a high value of V_oc. The obtained short-circuit photocurrent (J_sc) values are discussed and justified in terms of mass-transport limitation processes in the viscous ionic liquid electrolyte.