Enhancing Light-Emitting Efficiency of Blue Through-Space Charge Transfer Emitters via Fixing Configuration Induced by Intramolecular Hydrogen Bonding
Quanwei Li, Zhennan Zhao, Haisong Zhao, Yumeng Guo, Xingwen Tong, Shouke Yan, Zhongjie Ren
Abstract
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 (>10 7 s –1 ) and photoluminescence quantum yield (nearly 90%) are achieved. The corresponding blue organic light-emitting diodes show maximum external quantum efficiencies (EQE max ) 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 EQE max of 29.3% with a CIE coordinate of (0.12, 0.16) and a narrow emission.