Efficient visible-to-ultraviolet(UV)triplet-triplet annihilation upconversion(TTA-UC)with large anti-Stokes shift is highly promising for solar-powered and indoor applications.Nonetheless,the excitationwavelengthis co...Efficient visible-to-ultraviolet(UV)triplet-triplet annihilation upconversion(TTA-UC)with large anti-Stokes shift is highly promising for solar-powered and indoor applications.Nonetheless,the excitationwavelengthis confined to the blue region(<450 nm),mainly due to large energy loss during triplet sensitization,resulting in reduced photon utilization efficiency in practical scenarios.Herein,a series of multiple resonance thermally activated delayed fluorescence(MR-TADF)compounds are developed as purely organic sensitizers for the purpose of energy-loss reduction,which also feature intense absorbance in the visible region,high intersystem crossing efficiencies,and long triplet lifetimes.By pairing the MR-TADF sensitizers with appropriate acceptors,green-to-UV TTA-UC systems were realized with an anti-Stokes shift up to 1.05 eV,upconversion quantum yield up to 8.6%,and threshold excitation intensity as low as 9.2 mW cm^(−2) in solution.The TTA-UC pairs were applied as internal or external sources of UV photons to trigger energy-demanding photopolymerization and photoligation reactions even under excitation of low-power-density green light-emitting diode light,revealing the broad utility of thesemolecular upconverters.This work unlocks the huge potential of MR-TADF-type sensitizers in upconversion applications.展开更多
基金This research was made possible as a result of several generous grants from the National Natural Science Foundation of China(grant nos.51903159 and 91833304)the Shenzhen Science and Technology Program(grant nos.KQTD20170330110107046 and JCYJ20190808151209557).
文摘Efficient visible-to-ultraviolet(UV)triplet-triplet annihilation upconversion(TTA-UC)with large anti-Stokes shift is highly promising for solar-powered and indoor applications.Nonetheless,the excitationwavelengthis confined to the blue region(<450 nm),mainly due to large energy loss during triplet sensitization,resulting in reduced photon utilization efficiency in practical scenarios.Herein,a series of multiple resonance thermally activated delayed fluorescence(MR-TADF)compounds are developed as purely organic sensitizers for the purpose of energy-loss reduction,which also feature intense absorbance in the visible region,high intersystem crossing efficiencies,and long triplet lifetimes.By pairing the MR-TADF sensitizers with appropriate acceptors,green-to-UV TTA-UC systems were realized with an anti-Stokes shift up to 1.05 eV,upconversion quantum yield up to 8.6%,and threshold excitation intensity as low as 9.2 mW cm^(−2) in solution.The TTA-UC pairs were applied as internal or external sources of UV photons to trigger energy-demanding photopolymerization and photoligation reactions even under excitation of low-power-density green light-emitting diode light,revealing the broad utility of thesemolecular upconverters.This work unlocks the huge potential of MR-TADF-type sensitizers in upconversion applications.
