Acta Chimica Sinica ›› 2023, Vol. 81 ›› Issue (6): 588-594.DOI: 10.6023/A23040153 Previous Articles     Next Articles

Article

基于手性三蝶烯的红光热激活延迟荧光聚合物及其有机发光二极管研究

王银凤a,b, 李猛a,b,*(), 陈传峰a,b,*()   

  1. a 中国科学院化学研究所 北京分子科学国家研究中心 分子识别与功能院重点实验室 北京 100190
    b 中国科学院大学 北京 100049
  • 投稿日期:2023-04-20 发布日期:2023-05-17
  • 作者简介:
    庆祝《化学学报》创刊90周年.
  • 基金资助:
    国家自然科学基金(92256304); 国家自然科学基金(22122111); 国家自然科学基金(91956119)

Chiral Triptycene-Based Red Thermally Activated Delayed Fluorescence Polymers and Their Organic Light-Emitting Diodes

Yinfeng Wanga,b, Meng Lia,b(), Chuanfeng Chena,b()   

  1. a CAS Key Laboratory of Molecular Recognition and Function, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190
    b University of Chinese Academy of Sciences, Beijing 100049
  • Received:2023-04-20 Published:2023-05-17
  • Contact: * E-mail: limeng@iccas.ac.cn; cchen@iccas.ac.cn
  • About author:
    Dedicated to the 90th anniversary of Acta Chimica Sinica.
  • Supported by:
    National Natural Science Foundation of China(92256304); National Natural Science Foundation of China(22122111); National Natural Science Foundation of China(91956119)

Chiral triptycene acridine (TpAc) has unique 3D structure, homoconjugation effect and two separate reaction sites. By using the design strategy of chiral electron donor-acceptor (D*-A) copolymerization, the triptycene-based non-conjugated chiral red thermally activated delayed fluorescence (TADF) polymers (R,R)-pTpAcBTZ and (S,S)- pTpAcBTZ were directly polymerized by using TpAC as chiral electron donor and 4,7-dibromobenzo[c][1,2,5]thiadiazole (BTZ) as the strong electron acceptor. The molecular weights of these chiral polymers were characterized by gel permeation chromatography (GPC), and the GPC analysis indicated that the number-average molecular weight (Mn) ranged from 37.9 kDa to 39.3 kDa with the polydispersity index (PDI) values from 1.99 to 2.02. The chiral polymers exhibited good solubility in common organic solvents, such as chlorobenzene, tetrahydrofuran, dichloromethane and chloroform, ensuring good film quality during solution processing. In addition, the chiral TADF polymers showed excellent thermal stability with thermal decomposition temperature (Td) (corresponding to a 5% weight loss) around 440 ℃, and glass transition temperatures (Tg) were also detected in these chiral polymers when they were heated to 300 ℃, which could be ascribed to their highly rigid and twisted structures. According to the onset of the oxidation curve, the highest occupied molecular orbital (HOMO) energy levels of the chiral polymers were estimated to be -5.27 eV. Their corresponding optical energy band gaps were estimated to be 2.21 eV from the onset of their ultraviolet-visible (UV-Vis) absorption spectra in toluene. Consequently, the corresponding lowest unoccupied molecular orbital (LUMO) energy levels were calculated to be -3.06 eV. The S1 and T1 values of pTpAcBTZ were 2.13 eV and 2.05 eV, respectively, which were determined at 77 K, and the corresponding ΔEST was 0.08 eV which were favorable for reverse intersystem crossing of excitons from T1 to S1 states. The chiral TADF polymers showed efficient red TADF (λtoluene=663 nm) activity, and they also displayed mirror-image red circularly polarized luminescence (CPL) signals, with the |glum| of approximately 1.4×10-3. By using the chiral red polymers as emitters, the obtained solution-processed red OLEDs displayed maximum electroluminescence peak of about 658 nm, and its turn-on voltage is 3.6 V at a brightness of 1.0 cd/m2. The device exhibited well device efficiency, with a maximum external quantum efficiency of 2.0%, maximum current efficiency of 1.1 cd/A, maximum power efficiency of 0.8 lm/W. The design of the non-conjugated chiral polymers and their red TADF activity are conducive to promoting the development of related research fields such as chiral luminescent materials and red luminescence devices.

Key words: thermally activated delayed fluorescence, circularly polarized luminescence, polymer, triptycene, red luminescence