Novel multifunctional fluorene-phenanthroimidazole hybrid materials: Non-doped near-ultraviolet fluorescent emitter and host for green phosphorescent OLEDs

• Published in: Dyes and pigments 2021-02, Vol.186, p.109019, Article 109019
• Main Authors: Guan, Hui-Min, Hu, Yong-Xu, Xie, Dong-Dong, Chi, Hai-Jun, Xiao, Guo-Yong, Lv, Yan-Li, Li, Xiao, Zhang, Dong-Yu, Hu, Zhi-Zhi
• Format: Article
• Language: English
• Subjects: Fluorene; Host; Near-ultraviolet emission; OLEDs; Phenanthroimidazole
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2020.109019

Deep-blue-emissive host materials are crucial to achievement of high-performance full-color organic light-emitting diodes (OLEDs), simplifying the manufacturing process and reducing production costs. To develop efficient deep-blue-emissive host materials is still challenging. By incorporating 9,9-diphenylfluorene moiety into phenanthroimidazole via the insulating N1 position of imidazole, two fluorene-phenanthroimidazole hybrid near-ultraviolet-emitting materials FL-PI and FL-BPI were designed and synthesized. The photophysical property, thermal and amorphous ability, electrochemical property and electron structure could be effectively regulated by molecular design strategy. Both FL-PI and FL-BPI exhibited moderate near-ultraviolet emission (0.50/0.63), high triplet energy level (2.58/2.57eV), high thermostability (Td: 371/542 °C; Tg: 134/210 °C) and carrier-transporting nature. Non-doped near-ultraviolet OLEDs adopting FL-BPI emitter showed the maximum efficiencies of 5.4%, 3.8 cd A−1 and 2.8 lm W−1 with the CIE coordinates of (0.15, 0.05). In addition, FL-PI/FL-BPI-hosted green phosphorescent OLEDs demonstrated the maximum efficiencies of 16.3%, 28.8 cd A−1, 21.1 lm W−1 and 21.1%, 75.3 cd A−1, 27.8 lmW−1, respectively. Moreover, the external quantum efficiencies of FL-PI/FL-BPI-hosted green phosphorescent devices remained as high as 16.1% and 21.0% at 1000 cd m−2. This work demonstrates that the strategy for the development of near-ultraviolet high-emissive host materials is feasible. [Display omitted] •NUV fluorene-phenanthroimidazole fluorescent emitter FL-BPI is synthesized.•FL-BPI-based OLEDs emit NUV light with the CIE1931 coordinates of (0.15, 0.05).•Non-doped OLEDs with FL-BPI emitter demonstrate the maximum EQE of 5.4%.•FL-BPI-hosted green phosphorescent OLEDs exhibit outstanding performances.