Issue 1, 2023

New high-Tg bipolar benzimidazole derivatives in improving the stability of high-efficiency OLEDs

Abstract

Four bipolar molecules, named 1-, 2-, 3-, and 4-3cbzBIZ, composed of tricarbazole (3cbz) substituted benzimidazole, were synthesized and characterized. They not only exhibit good thermal stability with remarkably high glass transition temperatures and decomposition temperatures, especially 4-3CbzBIZ (Tg > 193 °C, Td > 453 °C), but also show superior thermal photoluminescence stability at elevated temperatures. Their morphological stabilities have also been affirmed using atomic force microscopy pictures after 30 min during 80 °C annealing. The FIrpic doped 4-3cbzBIZ organic light-emitting diode (OLED) shows sky-blue electroluminescence from FIrpic with a high external quantum efficiency (ηEQE) of 28.6% with an amazingly small efficiency roll-off (ηEQE = 27.3% at a luminance of 1000 cd m−2). Furthermore, the green OLED with Ir(ppy)3 doped in 4-3cbzBIZ exhibits excellent device thermal stability and a longer operational lifetime than the OLED with CBP as the host. In particular, a significant lifetime improvement by 11.6 times was obtained at an elevated temperature of 80 °C. The high efficiency and high-temperature stability of the OLED were ascribed to the balanced bipolar carrier-transporting properties, high Tg and rigidity of 4-3cbzBIZ. The present work of developing orthogonally linked donor–acceptor hosts provides a strategy of material design to develop high thermal stability OLEDs.

Graphical abstract: New high-Tg bipolar benzimidazole derivatives in improving the stability of high-efficiency OLEDs

Supplementary files

Article information

Article type
Paper
Submitted
30 9 2022
Accepted
21 11 2022
First published
25 11 2022

J. Mater. Chem. C, 2023,11, 161-171

New high-Tg bipolar benzimidazole derivatives in improving the stability of high-efficiency OLEDs

S. Lin, Y. Cheng, C. Chen, Y. Zhang, J. Lee, M. Leung, B. Lin and T. Chiu, J. Mater. Chem. C, 2023, 11, 161 DOI: 10.1039/D2TC04143J

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