Imidazolium Functionalized Bis-2,2,6,6-Tetramethyl-piperidine-1-oxyl (TEMPO) Bi-redox Couples for Highly Efficient Dye-Sensitized Solar Cells

•We synthesize imidazolium functionalized bis-TEMPO redox couple.•We prepare PMII/Im-bisTEMPO based hybrid electrolyte.•The PMII/Im-bisTEMPO based hybrid electrolyte shows high redox potential.•The dye-sensitized solar cells achieve a power conversion efficiency of 8.8%.

Imidazolium functionalized mono- and bis-TEMPO, 1-methyl-3-(4-(2,2,6,6-tetramethyl- 1-oxyl-4-piper-idoxyl)butyl)imidazolium bis(trifluoromethanesulfonyl) imide ([Im-TEMPO][TFSI]) and 1,3-bis(4-(2,2,6,6-tetramethyl-1-oxyl-4-piper-idoxyl)butyl)imidazolium bis(trifluoromethane- sulfonyl) imide ([Im-bisTEMPO][TFSI]), are synthesized and characterized. The prepared TEMPO based hybrid electrolyte shows negligible absorption in the visible region. Compared with the traditional I3−/I−, TEMPO/I−, Im-TEMPO/I− redox couples, [Im-bisTEMPO][TFSI]/I− hybrid redox couple displays the highest short circuit current density (Jsc), open circuit voltage (Voc) values, and exhibited an overall power conversion efficiency of 8.8% under simulated AM 1.5 solar spectrum irradiation at 100 mW cm-2. The enhanced photovoltaic performance might due to the lower electron recombination dynamics, negligible absorption in visible region of hybrid electrolytes and higher redox potential of the Im-bisTEMPO based redox couple.

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