The 2,2,6,6-tetramethyl-l-piperidinyloxy radical: An efficient, iodine-free redox mediator for dye-sensitized solar cells

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-piperidinytoxy (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 μm photoanode made from TiO 2 mesoscopic particles and an organic sensitizer with a high molar extinction coefficient yield an overall sokr-to-electric power conversion efficiency of 5.4 % under AM 1.5 illumination at 100 mW cm-2, which is unprecedented for an iodine-free mediator system. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA,.