具有快上转化速率的窄光谱蓝光多重共振发光材料

Blue multiple resonance emitters exhibiting fast spin flip

如何提高蓝光多重共振发光材料的反隙间窜跃速率(kRISC),并维持较快的辐射跃迁速率(kR)是促进其进一步发展和应用的关键.本论文报道了一种简单且高效的“空间限制的受体-供体-受体(SCADA)”策略,旨在加速蓝色多重共振发光分子的上转化过程.在多重共振中心骨架的最高占据轨道(HOMO)分布位点引入两个氰基苯受体,并在最低位占据轨道(LUMO)引入一个叔丁基咔唑给体,使发射波长蓝移的同时,减小发射的半峰宽(FWHM).此外,供体单元和受体单元呈现近距离的面对面取向,产生分子内给受体相互作用,进而增强自旋轨道耦合,加速反隙间窜跃过程.基于“SCADA”策略,本文成功开发出蓝光多重共振发光分子2DCNCz-BN,其FWHM仅为19 nm,并同时具有较快的kRISC(1.8×10^(6) s^(−1))和kR(2.0×10^(8) s^(−1)).以2DCNCz-BN为发光分子的OLED器件,最大外量子效率(EQEmax)为30.2%,并展现出较低的效率滚降,在1000 cd m^(−2)的亮度下,EQE可以维持22.3%.

The ongoing pursuit of developing high-performance narrowband blue multiple resonance(MR)emitters that feature a fast reverse intersystem crossing(RISC)rate(kRISC)presents a significant challenge.To address this,we introduce an efficient approach:The“space-confined acceptor-donor-acceptor(SCADA)”strategy,aiming at accelerating the RISC process in the development of blue MR emitters.By integrating two cyanobenzene acceptors and one carbazole donor onto the MR skeleton results,we achieve a blue-shifted emission with a reduced full width at half maximum(FWHM).This structural arrangement encourages the donor and acceptor units to align face-to-face at close proximity,which leads to intramolecular noncovalent interactions and enhances spin-orbit coupling.Consequently,the“SCADA”strategy gives rise to a superior blue MR emitter characterized by a small FWHM of 19 nm,a fast kRISC of 1.8×10^(6) s^(−1),as well as a fast radiative decay rate(kR)of 2.0×10^(8) s^(−1).These attributes facilitate the assembly of high-performance narrowband blue organic light-emitting diodes with a high maximum external quantum efficiency of 30.2%and low efficiency roll-off.