Controlling excited state properties to achieve fast reverse intersystem crossing rates of over 107 s-1 is still challenging for intramolecular through-space charge transfer (TSCT) based delayed fluorescent materials. To gain further insight into the relationship between through-space and through-bond charge transfer (TSCT/TBCT), herein, three compounds DPS-24Ac, DPS-25Ac and DPS-OAc were prepared and characterized via NMR, MS and single crystal, in which the diphenylsulfone (DPS) is used as the acceptor group and acridine (Ac) as the donor moiety. Intense emissions from blue to yellow with high emission efficiency of 70-100% are detected for all emitters. Both computations and experiments suggest that compounds DPS-24Ac and DPS-25Ac have a clear TSCT effect and also an inverted adiabatic singlet-triplet gap which can be explained by the kinetic exchange mechanism. Notably, compound DPS-24Ac achieves the highest reverse intersystem crossing rate constant (krISC) of over 107 s-1 via manipulation of both TSCT and TBCT effects. The solution-processed devices display maximum external quantum efficiencies of 21.73, 12.14 and 4.96% for DPS-24Ac, DPS-25Ac and DPS-OAc, respectively. Overall, this work provides a novel avenue to achieve highly-efficient OLED materials with fast rISC by controlling both TSCT and TBCT effects.
Ultrafast terahertz spectroscopy provides insight into charge transfer efficiency and dynamics in artificial photosynthesis
