Elimination Of 50% Iodine And Excellent Performance Of Dye-Sensitized Solar Cell Enabled By Tempo Radical Dendrimer-Iodide Dual Redox Systems

Detrimental effect of counter electrode corrosion, electrolyte leakage problem, and sublimation of iodine ions affect the performance and stability of dye-sensitized solar cells (DSSCs) based on a liquid redox electrolyte system. TEMPO/TEMPO+ is the most desirable one to replace the existing redox couples in liquid electrolyte owing to its rapid and reversible one electron kinetics, high diffusion coefficient, and electrochemical stability. In the present study, a fifth generation polyurethane dendrimer end-capped with 2,2,6,6-tetrame-thylpiperidin-1-oxyl (TEMPO) was prepared and employed as an active redox mediator to replace up to 75% of iodine ions in the standard liquid iodide electrolyte system to elucidate the effect of a quick self-exchange reaction in DSSCs. In this concern, quasi-gel type electrolytes were prepared by incorporating different amounts of a newly prepared TEMPO radical dendrimer to a liquid I-/I-3(-) redox system and were used as a dual redox mediator for DSSCs. Blending of 50 wt % of I-/I-3(-) electrolyte with 50 wt % of the radical dendrimer improved the device performance (eta) unprecedentedly from 6.56 to 9.54% upon illumination with 1 sun intensity. Thorough electrochemical characterization of cells was carried out and all such parameters authenticated this remarkable enhancement. Stability of the device was also found to be good, which retained its >80% efficiency after 30 days.