Spiro‐sulfone‐based Auxiliary Acceptor in D‐A‐π‐A Dye‐sensitized Solar Cells Application under Indoor/Outdoor Light

다국어 초록 (Multilingual Abstract)

Novel D−A‐π‐A type organic sensitizers (YS‐1 & YS‐2) with spiro[fluorene‐9,9′‐thioxanthene]‐10′,10′‐dioxide as an auxiliary acceptor were synthesised and effectively fabricated in dye‐sensitised solar cells (DSSCs). The sensitizer structures were modified by introducing an auxiliary acceptor of spiro[fluorene‐9,9′‐thioxanthene]‐10′,10′‐dioxide between the donor and the π‐bridge moieties. The bulky auxiliary acceptor can suppress intermolecular aggregation, and the sulfone group can enhance Li+ ions trapping to retard charge recombination. The sensitizer YS‐2 performed power conversion efficiency of 4.21% under AM1.5 solar condition. Both YS‐1 and YS‐2 displayed higher light conversion efficiency than N719 in the wavelength range of 300∼500 nm. Therefore, mixing N719 with YS‐2 in a co‐sensitized test displayed an efficiency of 8.66% under one sun (AM 1.5G). While operated under CWF and TL84 indoor light, the efficiency was boosted to 22.45% and 24.72%, respectively, at 2500 lux illumination. The high co‐sensitization performance of mixing N719 and YS‐2 can be ascribed to the high absorption efficiency of YS‐2 at short‐wavelength, which is a shortcoming of N719 sensitizer. The high performance of N719 and YS‐2 co‐sensitization is mainly due to a better surface coverage on TiO2 surface. The durability test of the device co‐sensitized with N719 and YS‐2 showed a mild decay of PCE from 24.7% to 16.8% (68% maintenance) after 336 h in ambient atmosphere without encapsulation. In a comparison, the device made with bare‐N719 starting with a PCE of 19.49% dropped to 3.87% (20% maintenance) under the same condition.
Through co‐sensitization of YS‐2 and N719, the DSSCs exhibited a PCE of 8.66% under one sun (AM 1.5G) illumination and 24.72% under 2500 lux indoor light, respectively, using a TL84 fluorescent lamp.