Achieving Enhanced Thermally Activated Delayed Fluorescence Rates and Shortened Exciton Lifetimes by Constructing Intramolecular Hydrogen Bonding Channels

• DOI: 10.1021/acsami.9b16073
• Publication Date: 2019-11-13T13:38:21Z
• Authors: Liangying Wang; Xinyi Cai; BinBin Li; Mengke Li; Zhiheng Wang; Lin Gan; Zhenyang Qiao; Wentao Xie; Qiumin Liang; Nan Zheng; Kunkun Liu; Shi-Jian Su
• Keywords: 02 engineering and technology; 0210 nano-technology; 7. Clean energy

A fast radiative rate, highly suppressed nonradiation, and a short exciton lifetime are key elements for achieving efficient thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) with reduced efficiency roll-off at high current density. Herein, four representative TADF emitters designed synthesized based on the combination of benzophenone (BP) or 3-benzoylpyridine (BPy3) acceptors, dendritic 3,3″,6,6″-tetra-tert-butyl-9′H-9,3′:6′,9″-tercarbazole (CDTC) 10H-spiro(acridine-9,9′-thioxanthene) (TXDMAc) donors, respectively. Density functional theory simulation X-ray diffraction analysis validated formation CH···N intramolecular hydrogen bonds regarding BPy3-CDTC BPy3-TXDMAc compounds. Notably, construction bonding within significantly enhances charge transfer (ICT) strength while reducing donor–acceptor (D-A) dihedral angle, resulting in accelerated nonradiative processes. With lifetimes (τTADF) photoluminescence quantum yields (ϕPL), OLEDs employing dopants realized maximum external efficiencies (EQEs) up to 18.9 25.6%, Moreover, nondoped device exhibited EQE 18.7%, accompanied by an extremely small loss only 4.1% luminance 1000 cd m–2. In particular, operational sky-blue BPy3-CDTC-based was greatly extended 10 times contrast BP-CDTC-based counterpart, verifying idea that in-built strategy promising realization stable TADF-OLEDs.