Abstract
A promising redox system, offering an alternative to the widely used iodide/triiodide couple, based on the stable organic radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) has been employed in dye-sensitized solar cells. The photovoltaic performance of this new redox couple has been evaluated by employing nanocrystalline TiO2 films with different thickness. Judicious selections of a 5.0 mu m photoanode made from TiO2 mesoscopic particles and an organic sensitizer with a high molar extinction coefficient yield an overall solar-to-electric power conversion efficiency of 5.4 % under AM 1.5 illumination at 1 00 MW cm(-2), which is unprecedented for an iodine-free mediator system.