Acta Chimica Sinica ›› 2020, Vol. 78 ›› Issue (2): 140-146.DOI: 10.6023/A19100372 Previous Articles     Next Articles



王志强a, 白美丹b, 张明b, 张智强c, 冯勋a, 郑才俊b   

  1. a 洛阳师范学院化学化工学院 河南省功能导向多孔材料重点实验室 洛阳 471934;
    b 电子科技大学光电科学与工程学院 成都 610054;
    c 郑州轻工业大学材料与化学工程学院 郑州 450001
  • 投稿日期:2019-10-16 发布日期:2019-12-31
  • 通讯作者: 王志强, 张智强, 郑才俊;;
  • 基金资助:

Synthesis and Properties of Two Novel Thermally Activated Delayed Fluorescence Materials with 1,3,5-Tribenzoylbenzene as Electron-Acceptor

Wang Zhiqianga, Bai Meidanb, Zhang Mingb, Zhang Zhiqiangc, Feng Xuna, Zheng Caijunb   

  1. a College of Chemistry and Chemical Engineering and Henan Key Laboratory of Function-Oriented Porous Materials, Luoyang Normal University, Luoyang 471934;
    b School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China(UESTC), Chengdu 610054;
    c Department of Material and Chemical Engineering, Zhengzhou University of Light Industry, Zhengzhou 450001
  • Received:2019-10-16 Published:2019-12-31
  • Supported by:
    Project supported by the National Natural Science Foundation of China (No. 51773029) and the Henan Natural Science Foundation (No. 182300410230).

Two thermally activated delayed fluorescence (TADF) materials TBP-DmCz and TBP-TmCz were successfully synthesized using 1,3,5-tribenzoylbenzene (TBP) as electron-acceptor, 1,8-dimethylcarbazole (DmCz) and 1,3,6,8-tetra-methylcarbazole (TmCz) as electron-donor, respectively. Thermal gravimetric analysis show that the thermal decomposition temperatures (Td) are 479℃ for TBP-DmCz and 484℃ for TBP-TmCz and no glass transition was found for both materials during the differential scanning calorimetry investigations. The highest occupied molecular orbitals (HOMO) are confined on the carbazole unit, while the lowest unoccupied molecular orbitals (LUMO) are located on the 1,3,5-tribenzoylbenzene unit, and there is almost no overlap between HOMO and LUMO, which is the typical molecular orbital character of TADF materials. Meanwhile, TBP-DmCz and TBP-TmCz possess degenerated HOMO and LUMO, which would promote the radiative transitions as the transitions could take place from all degenerated LUMOs to HOMOs. The HOMO level of TBP-TmCz is obviously higher than that of TBP-DmCz due to increasing the number of methyl groups at the electron-donor carbazole, and the LUMO levels of TBP-DmCz and TBP-TmCz only show a small difference because these materials have the same electron-acceptor 1,3,5-tribenzoylbenzene. In toluene solution, these materials have very similar absorption spectra and exhibit absorption bands assigned to intramolecular charge-transfer transition. The spectral peaks are located at 488 nm for TBP-DmCz and 502 nm for TBP-TmCz, respectively, in toluene solution at room temperature. According to the fluorescence and phosphorescence spectra of these materials in 1,3-bis(N-carbazolyl)benzene (mCP) film at 77 K, the energy gaps between the lowest singlet and triplet (ΔEST) of TBP-DmCz and TBP-TmCz are calculated to be 0.05 and 0.01 eV, respectively. The fluorescence decay behaviors at different temperatures (100, 200 and 300 K) proved that emissions of TBP-DmCz and TBP-TmCz contain TADF component. The electroluminescence devices with TBP-DmCz and TBP-TmCz as the emitters show high efficiency and low efficiency roll-off. The maximum external quantum efficiencies of devices based on TBP-DmCz and TBP-TmCz are 13.6% and 18.3%, respectively.

Key words: electroluminescence, light-emitting material, thermally activated delayed fluorescence, 1,3,5-tribenzoylbenzene, carbazole