Liao Chuanxin, Wang Shirong, Chen Bo, Xie Qi, Feng Jingyuan, Bai Jiaxu, Li Xianggao, Liu Hongli
School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, 300072, China.
Angew Chem Int Ed Engl. 2025 Jan 10;64(2):e202414905. doi: 10.1002/anie.202414905. Epub 2024 Oct 30.
Hybrid local and charge transfer (HLCT) excited state materials, which possess weak donor-acceptor (D-A) pure organic structures, deserve one of the most promising efficient and stable blue emitters. Through high-lying reverse intersystem crossing (hRISC) process, 75 % triplet excitons generated by electrical excitation could be harvested and utilized in organic light-emitting diodes (OLEDs). However, there are still significant challenges to achieve high-efficiency ultra-deep-blue HLCT emitters with low Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinate y values. Here, a series of novel blue HLCT emitters based on spiro[1,8-diazafluorene-9,2'-imidazole] structure were designed and synthesized by fine-tuning the spiro[fluorene-9,2'-imidazole] core structure in our previous work through heteroatom substitution and hyperconjugation effect. The target emitters were endowed with excellent photophysical and electrochemical merits, thermal stability and solution processibility. The solution-processed OLED based on 4',5'-bis(4-(9H-carbazol-9-yl)phenyl)spiro[1,8-diazafluorene-9,2'-imidazole] (NFIP-CZ) achieved efficient ultra-deep-blue emission (CIE=0.1581, 0.0422) with the maximum external quantum efficiency (EQE), maximum current efficiency (CE) and maximum power efficiency (PE) of 11.94 %, 4.07 cd ⋅ A and 2.56 lm ⋅ W. The record EQE is a breakthrough in both solution-processed and vacuum vapor deposition ultra-deep-blue HLCT OLEDs currently.
混合局域和电荷转移（HLCT）激发态材料具有较弱的供体-受体（D-A）纯有机结构，是最有前景的高效稳定蓝色发光体之一。通过高位反向系间窜越（hRISC）过程，电激发产生的75%的三重态激子可在有机发光二极管（OLED）中被收集和利用。然而，要实现具有低国际照明委员会（CIE）1931色度坐标y值的高效超深蓝光HLCT发光体仍面临重大挑战。在此，基于我们之前工作中通过杂原子取代和超共轭效应微调螺[芴-9,2'-咪唑]核心结构，设计并合成了一系列基于螺[1,8-二氮杂芴-9,2'-咪唑]结构的新型蓝色HLCT发光体。目标发光体具有优异的光物理和电化学特性、热稳定性以及溶液可加工性。基于4',5'-双（4-（9H-咔唑-9-基）苯基）螺[1,8-二氮杂芴-9,2'-咪唑]（NFIP-CZ）的溶液加工OLED实现了高效超深蓝光发射（CIE = 0.1581, 0.0422），最大外量子效率（EQE）、最大电流效率（CE）和最大功率效率（PE）分别为11.94%、4.07 cd·A和2.56 lm·W。该创纪录的EQE在目前的溶液加工和真空蒸镀超深蓝光HLCT OLED中都是一个突破。
