title: Tuning the singlet-triplet energy gap of AIE luminogens: crystallization-induced room temperature phosphorescence and delay fluorescence, tunable temperature response, highly efficient non-doped organic light-emitting diodes.
abstract: In this contribution, we finely tuned the singlet-triplet energy gap (ΔEST) of AIE-active materials to modulate their fluorescence, phosphorescence and delay fluorescence via rational molecular design and investigated the possible ways to harvest their triplet energy in OLEDs. Noteworthily, two molecules o-TPA-3TPE-o-PhCN and o-TPA-3TPE-p-PhCN with larger ΔEST values (0.59 eV and 0.45 eV, respectively) emitted efficient long-lived low temperature phosphorescence in their glassy solutions and exhibited efficient crystallization-induced room temperature phosphorescence (RTP). Meanwhile, it was the first time to observe a novel crystallization-induced delay fluorescence phenomenon in another AIE-active molecule p-TPA-3TPE-p-PhCN owing to its very small ΔEST value (0.21 eV). It was also found that molecules with various ΔEST values showed significantly different temperature sensitivity. Non-doped electroluminescent (EL) devices using these molecules as light-emitting layers were fabricated, exhibiting external quantum efficiencies (EQE) higher than theoretical values of purely singlet emitter type devices. Particularly, p-TPA-3TPE-p-PhCN showed outstanding device performances with high luminance and efficiencies up to 36,900 cd m(-2), 11.2 lm W(-1), 12.8 cd A(-1) and 4.37%, respectively, considering that its solid-state quantum yield was only 42%. All the above observations suggested that tuning the ΔEST values of AIE materials is a powerful methodology to generate many more interesting and meaningful optoelectronic properties.
authors.affiliation: Department of Chemistry, Institute for Advanced Study, Division of Life Science, Institute of Molecular Functional Materials, Division of Biomedical Engineering and State Key Laboratory of Molecular Neuroscience, the Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong, China. tangbenz@ust.hk.
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Yibin
authors.initials: Y
authors.lastname: Jiang
authors.forename: Juan
authors.initials: J
authors.lastname: Cheng
authors.forename: Yilin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Huimin
authors.initials: H
authors.lastname: Su
authors.forename: Jacky W Y
authors.initials: JW
authors.lastname: Lam
authors.forename: Herman H Y
authors.initials: HH
authors.lastname: Sung
authors.forename: Kam Sing
authors.initials: KS
authors.lastname: Wong
authors.forename: Hoi Sing
authors.initials: HS
authors.lastname: Kwok
authors.forename: Ben Zhong
authors.initials: BZ
authors.lastname: Tang
mesh_terms: D002911:Chrysenes / Q000737:chemistry*; D003460:Crystallization; D004579:Electron Transport; D005453:Fluorescence; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D012666:Semiconductors; D013696:Temperature
chemical_list: D002911:Chrysenes; C009590:triphenylene