A sp2-carbon-linked covalent organic framework containing tetraphenylethene units used as yellow phosphors in white light-emitting diodes

• Published in: Polymer (Guilford) 2022-02, Vol.241, p.124474, Article 124474
• Main Authors: Li, Xianghua, Tang, Huaijun, Gao, Long, Chen, Zeyu, Li, Haoju, Wang, Yuhong, Yang, Kaixin, Lu, Shiyou, Wang, Kaimin, Zhou, Qiang, Wang, Zhengliang
• Format: Article
• Language: English
• Subjects: Carbon; Chromaticity; Color; Color temperature; Covalent organic framework; Epoxy resins; Ethene; Ethylene; Gallium nitrides; Light emitting diodes; Luminous efficacy; Monomers; Phosphor; Phosphors; sp2-carbon-linkage; Tetraphenylethylene; Thermal decomposition; Thermal stability; White light; White light-emitting diode; X ray powder diffraction; X-ray diffraction
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2021.124474

A sp2-carbon-linked covalent organic framework (COF) containing tetraphenylethene units was successfully synthesized by using 2,2'-(1,4-phenylene)diacetonitrile and 4′,4‴,4‴'',4‴'''-(Ethene-1,1,2,2-tetrayl)tetrakis(([1,1′-biphenyl]-4-carbaldehyde)) as monomers. After being investigated by powder X-Ray diffraction (PXRD), nitrogen adsorption-desorption and theoretical calculations, the dual-pore eclipsed Kagome structure (AA-K) of the COF was confirmed. The COF emitted bright yellow light with a solid-state photoluminesce quantum yield (PLQY) of 39.2%. It exhibited high thermal stability with a thermal decomposition temperature (Td) of ca. 610 °C, and its relative emission intensity at 90 °C was nearly 80.0% of that at 30 °C. The COF was blended in epoxy resin at different concentrations and used as phosphors, excited by GaN-based blue-emitting chips (λem,max ≈ 455 nm), a series of white light-emitting diodes (WLEDs) with different correlated color temperature (CCT) can be obtained. At 1.5 wt%, a cold WLED was obtained, its CCT was 6125 K, color rendering index (CRI) was 83.4, Commission Internationale de L'Eclairage (CIE) chromaticity coordinate was (0.32, 0.29), luminous efficiency (ηL) was 20.31 lm·W−1. At 2.0 wt%, a neutral WLED was obtained, its CCT was 4293 K, CRI was 79.6, chromaticity coordinate was (0.36, 0.34) and ηL was 19.71 lm·W−1. At 2.5 wt%, a warm WLED was obtained, its CCT was 3348 K, CRI was 69.4, chromaticity coordinate was (0.42, 0.42) and ηL was 18.81 lm·W−1. The results suggested the COF can be used promising metal-free phosphors in WLEDs. [Display omitted] •A sp2-carbon-linked covalent organic framework (COF) containing tetraphenylethene units was synthesized.•The COF emitted bright yellow light with a solid-state photoluminesce quantum yield (PLQY) of 39.2%.•The thermal decomposition temperature (Td) of the COF was as high as 610 °C.•Cold/neutral/warm white LEDs with high performances were prepared by using the COF and blue-emitting chips.