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Issue 2, 2015
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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

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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.

Graphical abstract: 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

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Publication details

The article was received on 10 Sep 2014, accepted on 13 Nov 2014 and first published on 14 Nov 2014


Article type: Paper
DOI: 10.1039/C4CP04052J
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Citation: Phys. Chem. Chem. Phys., 2015,17, 1134-1141

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    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

    J. Li, Y. Jiang, J. Cheng, Y. Zhang, H. Su, J. W. Y. Lam, H. H. Y. Sung, K. S. Wong, H. S. Kwok and B. Z. Tang, Phys. Chem. Chem. Phys., 2015, 17, 1134
    DOI: 10.1039/C4CP04052J

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