Manipulating charge carrier transporting of disubstituted phenylbenzoimidazole-based host materials for efficient full-color PhOLEDs

Abstract Many efforts have been focused on exploring highly efficient host materials that capable of function in phosphorescent organic light-emitting devices (PhOLEDs). However, superior hosts reported to date that are generally suitable to full-color devices are rare and the resultant device performances are far from satisfactory. A class of host compounds DCzPBI, POCzPBI, and DPOPBI, incorporating carbazole and diphenylphosphoryl oxide moieties as electron-donating and -accepting groups, respectively, are synthesized and successfully applied as universal hosts in the fabrication of full-color PhOLEDs. The effect of substituted groups on the photophysical, theoretical calculations, and electrochemical characters for host materials is systematically investigated. We adopt the same device architecture to fabricate the blue, green, yellow, and red PhOLEDs with the combination of the three hosts. As a result, DPOPBI and POCzPBI with good charge carrier transporting properties supported the devices with the impressive efficiencies. The best current efficiency (CE) are 23.2, 48.4, 45.7, 21.5 cd A−1 for blue, green, yellow, and red devices, respectively. Even at the brightnesses of 1000 cd m−2, the efficiency roll-offs are only 2% for green and 0.2% for yellow devices, indicating the promising applications as universal hosts for highly efficient PhOLEDs.