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Issue 29, 2011
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Construction of efficient solid emitters with conventional and AIE luminogens for blue organic light-emitting diodes

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Abstract

9,9-Bis(9-heptyl-3-carbazolyl)fluorenes (BPyBCF, BAnBCF, BTPABCF, and BTPEBCF, where B = Bis, Py = pyrene, C = carbazole, F = fluorene, An = anthracene, TPA = triphenylamine, and TPE = tetraphenylethene) with different chromophoric units at the 2,7-positions are synthesized in moderate to high yields (52–89%) by Suzuki coupling reactions of 9,9-bis(9-heptyl-3-carbazolyl)-2,7-dibromofluorene with the corresponding arylboronic acid and utilized as active layers for the construction of blue organic light-emitting diodes (OLEDs). BPyBCF, BAnBCF and BTPABCF emit intense blue light with high fluorescence quantum yields (ΦF = 75–94%) in solution. However, they exhibit much lower ΦF values (30–61%) in the film state, revealing that aggregate formation has quenched their light emission. On the contrary, BTPEBCF is weakly emissive in solution (ΦF = 0.3%) but becomes a strong emitter (ΦF = 100%) when fabricated into solid film, demonstrating a phenomenon of aggregation-induced emission (AIE). Restriction of intramolecular rotation and suppression of intermolecular interactions due to the propeller-like tetraphenylethene unit are responsible for the AIE phenomenon. All the luminogens are thermally and morphologically stable, showing high glass-transition (Tg = 109–147 °C) and thermal-degradation temperatures (Td = 396–478 °C). Non-doped OLEDs using BPyBCF, BAnBCF, and BTPABCF as light-emitting layers are constructed, which give blue electroluminescence with maximum current (ηC,max) and external quantum (ηext,max) efficiencies of 4.8 cd A−1 and 2.3%. With the same device configuration, BTPEBCF shows higher ηC,max and ηext,max values of 7.9 cd A−1 and 2.9%, respectively, thanks to its AIE feature.

Graphical abstract: Construction of efficient solid emitters with conventional and AIE luminogens for blue organic light-emitting diodes

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Publication details

The article was received on 15 Jan 2011, accepted on 05 May 2011 and first published on 22 Jun 2011


Article type: Paper
DOI: 10.1039/C1JM10221D
Citation: J. Mater. Chem., 2011,21, 10949-10956
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    Construction of efficient solid emitters with conventional and AIE luminogens for blue organic light-emitting diodes

    Z. Zhao, S. Chen, C. Deng, J. W. Y. Lam, C. Y. K. Chan, P. Lu, Z. Wang, B. Hu, X. Chen, P. Lu, H. S. Kwok, Y. Ma, H. Qiu and B. Z. Tang, J. Mater. Chem., 2011, 21, 10949
    DOI: 10.1039/C1JM10221D

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