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Issue 44, 2019
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Highly efficient deep-blue light-emitting copolymers containing phenoxazine: enhanced device efficiency and lifetime by blending a hole transport molecule

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Abstract

A series of deep-blue light-emitting copolymers with an emission peak at 455 nm and narrow full width at half-maximum (FWHM) of about 40 nm were synthesized by incorporating a small amount of 10-(4-hexylphenyl)-10H-phenoxazine (PO) unit into the backbone of poly(9,9-dioctylfluorene). All the copolymers exhibit good thermal stability, high photoluminescent quantum yield and appropriate electrochemical energy levels. The copolymer PF-TD2PO1 which contains 1 mol% PO unit shows a maximum luminous efficiency (LEmax) of 3.07 cd A−1 and 5.18 cd A−1 based on single-layer and double-layer devices, respectively, with deep-blue Commission Internationale de L’E’clairage (CIE) coordinates of (0.15, 0.11). To improve the hole transport of the emissive layer, a hole transport molecule N-([1,1′-biphenyl]-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazo-yl)-phenyl)-9H-fluorene-2-amine (BCFN) was blended into PF-TD2PO1. As a result, the best electroluminescence performance with a low turn-on voltage of 3.0 V, a superior LEmax of 6.20 cd A−1 (corresponding to a maximum external quantum efficiency of 6.22%), an unprecedented luminance of 44 685 cd m−2 and deep-blue CIE coordinates of (0.15, 0.11) were obtained from the blended PF-TD2PO1:BCFN light emitting device. It is particularly important that PF-TD2PO1:BCFN based devices exhibit very slow efficiency roll-off and a more than 14 times enhanced lifetime compared with the devices without BCFN. The results indicate the great potential of this class of copolymers for application in solution processed deep-blue light-emitting diodes with high efficiency and long lifetime.

Graphical abstract: Highly efficient deep-blue light-emitting copolymers containing phenoxazine: enhanced device efficiency and lifetime by blending a hole transport molecule

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Publication details

The article was received on 27 Aug 2019, accepted on 04 Oct 2019 and first published on 07 Oct 2019


Article type: Paper
DOI: 10.1039/C9TC04721B
J. Mater. Chem. C, 2019,7, 13859-13866

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    Highly efficient deep-blue light-emitting copolymers containing phenoxazine: enhanced device efficiency and lifetime by blending a hole transport molecule

    J. He, Z. Huang, Z. Huang, S. Liao, F. Peng, Z. Zhong, T. Guo, L. Ying and Y. Cao, J. Mater. Chem. C, 2019, 7, 13859
    DOI: 10.1039/C9TC04721B

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