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

Deep-blue-emissive host materials are crucial to achievement of high-performance full-color organic lightemitting 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 degrees C; Tg: 134/210 degrees 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 mu m W-1 with the CIE coordinates of (0.15, 0.05). In addition, FL-PI/FL-BPIhosted 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 mu m W-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.

Automated summary

The designed FL-PI and FL-BPI materials show good near-ultraviolet emitting performance, high thermal stability, and carrier transporting nature.