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Crafting 1,4-diaryl spirobifluorene hosts in OLEDs interannular C-H arylation: synergistic effects of molecular linearity and orthogonality

In this work, we present a design concept of introducing linear structures into the orthogonal configuration of 9,9′-spirobifluorene (SBF), aiming to enhance carrier mobilities while maintaining high triplet energies ( E T ), which are two critical parameters for optimizing host materials in organic...

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Bibliographic Details
Published in:Chemical science (Cambridge) 2024-07, Vol.15 (27), p.1547-1555
Main Authors: Li, Qian, Yu, Zhiqian, Liu, Qianhui, Guo, Yusong, Fu, Zhangyi, Yang, Yudong, Bin, Zhengyang, Wu, Di, Lan, Jingbo
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Summary:In this work, we present a design concept of introducing linear structures into the orthogonal configuration of 9,9′-spirobifluorene (SBF), aiming to enhance carrier mobilities while maintaining high triplet energies ( E T ), which are two critical parameters for optimizing host materials in organic light-emitting diodes (OLEDs). To validate our proposed design, four pivotal model molecules of 1,4-diaryl SBFs were synthesized via interannular C-H arylation of bi(hetero)aryl-2-formaldehydes, a task challenging to accomplish using previous synthetic methodologies. The orthogonal configuration and the steric hindrance of SBF lead to high E T through the conjugation breaking at C1 and C4 positions, rendering 1,4-diaryl SBFs suitable as universal pure hydrocarbon (PHC) hosts for red, green, and blue (RGB) phosphorescent OLEDs (PhOLEDs). Meanwhile, the linearity and relatively good planarity of the para -quaterphenyl structure promote high carrier mobilities through orderly intermolecular packing. The synergistic effects of linearity and orthogonality in 1-( para -biphenyl)-4-phenyl-SBF result in exceptional device performance with external quantum efficiencies (EQEs) of 26.0%, 26.1%, and 22.5% for RGB PhOLEDs, respectively. Notably, the green PhOLED exhibits minimal efficiency roll-off, positioning its device performances among the state-of-the-art in PHC hosts. Design concept of introducing linear structure into orthogonal configuration is presented. To validate this concept, 1,4-diaryl spirobifluorenes are synthesized via interannular selective C-H arylation, proving to be excellent pure hydrocarbon hosts.
ISSN:2041-6520
2041-6539
DOI:10.1039/d4sc02178a