Hybridized through-bond/through-space charge transfer enables efficient blue emitters with the Rec. 2020 color gamut
Xihao Yang1, Yongxu Hu1, Xiaoyu Guo1
1Shenzhen Key Laboratory of New Information Display and Storage Materials, College of Materials Science and Engineering, Shenzhen University Shenzhen 518055 P. R. China liuhe001@szu.edu.cn.
None:
Achieving efficient deep-blue emission with high color purity remains a critical challenge for BT.2020-compliant OLEDs. Herein, we present a rational molecular design strategy by tuning the hybridization between through-bond charge transfer (TBCT) and through-space charge transfer (TSCT) in a series of A1-D1-D2-A2 structured TADF emitters. Two proof-of-concept emitters, BOtC and BOCC, were synthesized with symmetric and asymmetric 1,1'-bicarbazole donors, respectively. Comprehensive theoretical and photophysical analyses reveal that BOtC exhibits balanced TBCT/TSCT hybridization, leading to a small energy difference (ΔE ST) between the first singlet (S1) and triplet (T1) excited states, fast reverse intersystem crossing, and efficient triplet exciton utilization. In contrast, TSCT-dominated BOCC shows slower RISC and reduced exciton recycling. Consequently, BOtC-based OLEDs achieve deep-blue emission (CIE: 0.157, 0.047) and a high external quantum efficiency (EQE) of 14.4%, whereas BOCC-based devices display a lower EQE of 6.5%. This work establishes TBCT/TSCT hybridization control as a general strategy to simultaneously achieve high efficiency and ultrahigh color purity in blue TADF emitters, providing guidance for next-generation display applications.
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