Efficient Solid Emitters with Aggregation-Induced Emission and Intramolecular Charge Transfer Characteristics: Molecular Design, Synthesis, Photophysical Behaviors, and OLED Application

Abstract

Emissive electron donor–acceptor (D–A) conjugates have a wide variety of applications in biophotonics, two-photon absorption materials, organic lasers, long wavelength emitters, and so forth. However, it is still a challenge to synthesize high solid-state efficiency D–A structured emitters due to the notorious aggregation-caused quenching (ACQ) effect. Though some D–A systems are reported to show aggregation-induced emission (AIE) behaviors, most are only selectively AIE-active in highly polar solvents, showing decreased solid-sate emission efficiencies compared to those in nonpolar solvents. Here we report the triphenylamine (TPA) and 2,3,3-triphenylacrylonitrile (TPAN) based D–A architectures, namely, TPA3TPAN and DTPA4TPAN. Decoration of arylamines with TPAN changes their emission behaviors from ACQ to AIE, making resulting TPA3TPAN and DTPA4TPAN nonluminescent in common solvents but highly emissive when aggregated as nanoparticles, solid powders, and thin films owing to their highly twisted configurations. Both compounds also display a bathochromic effect due to their intramolecular charge transfer (ICT) attribute. Combined ICT and AIE features render TPA3TPAN and DTPA4TPAN intense solid yellow emitters with quantum efficiencies of 33.2% and 38.2%, respectively. They are also thermally and morphologically stable, with decomposition and glass transition temperatures ( T d / T g ) being 365/127 and 377/141 °C, respectively. Multilayer electroluminescence (EL) devices are constructed, which emit yellow EL with maximum luminance, current, power, and external quantum efficiencies up to 3101 cd/m 2, 6.16 cd/A, 2.64 lm/W, and 2.18%, respectively. These results indicate that it is promising to fabricate high efficiency AIE-ICT luminogens with tunable emissions through rational combination and modulation of propeller-like donors and/or acceptors, thus paving the way for their biophotonic and optoelectronic applications.