Enhancing Light-Emitting Efficiency of Blue Through-Space Charge Transfer Emitters via Fixing Configuration Induced by Intramolecular Hydrogen Bonding

Closely aligned configuration of the donor (D) and acceptor (A) is crucial for the light-emitting efficiency of thermally activated delayed fluorescence (TADF) materials with through-space charge transfer (TSCT) characteristics. However, precisely controlling the D–A distance of blue TSCT-TADF emitters is still challenging. Herein, an extra donor (D*) located on the side of the primary donor (D) is introduced to construct the hydrogen bonding with A and thus modulate the distance of D and A units to prepare high-efficiency blue TSCT emitters. The obtained “V”-shaped TSCT emitter presents a minimal D–A distance of 2.890 Å with a highly parallel D–A configuration. As a result, a high rate of radiative decay (>107 s–1) and photoluminescence quantum yield (nearly 90%) are achieved. The corresponding blue organic light-emitting diodes show maximum external quantum efficiencies (EQEmax) of 27.9% with a Commission Internationale de L’Eclairage (CIE) coordinate of (0.16, 0.21), which is the highest device efficiency of fluorene-based blue TSCT-TADF emitters. In addition, the TSCT-TADF emitter-sensitized OLEDs also achieve a high EQEmax of 29.3% with a CIE coordinate of (0.12, 0.16) and a narrow emission.给体（D）与受体（A）的紧密适配构型，对具备空间电荷转移（through-space charge transfer, TSCT）特性的热活化延迟荧光（thermally activated delayed fluorescence, TADF）材料的发光效率至关重要。然而，精准调控蓝色TSCT-TADF发光体的D-A间距仍颇具挑战。本研究通过在原生给体（D）的侧位引入额外给体（D*），使其与受体（A）形成氢键作用，进而调控D与A单元的间距，以此制备高效蓝色TSCT发光体。所得的"V"型TSCT发光体呈现出2.890 Å的最小D-A间距，且D-A构型高度平行。最终，该材料实现了超过10^7 s^-1的高辐射衰变速率，以及近90%的光致发光量子产率（photoluminescence quantum yield）。对应的蓝色有机发光二极管（organic light-emitting diodes, OLED）展现出27.9%的最大外量子效率，国际照明委员会（Commission Internationale de l’Eclairage, CIE）坐标为(0.16, 0.21)，这是基于芴的蓝色TSCT-TADF发光体的最高器件效率。此外，经TSCT-TADF发光体敏化的OLED也实现了29.3%的高最大外量子效率，CIE坐标为(0.12, 0.16)，且发射窄化。