High-performance red organic light-emitting devices based on an exciplex system with thermally activated delayed fluorescence characteristic

Abstract

To realize high-performance red organic light-emitting diodes (OLEDs), a novel exciplex system Tris-PCz:B4PyPPM with thermally activated delayed fluorescence (TADF) characteristic was developed as the host of both red fluorescent and phosphorescent emitters. Due to the blue-green PL spectrum and suitable triplet energy level of 2.53 eV, the exciplex system matches the requirements of both red fluorescent and phosphorescent dopants. With an optimized mixing molar ratio of 5:5, Tris-PCz:B4PyPPM exciplex system shows outstanding host performance in both the red fluorescent and phosphorescent devices. The red fluorescent device based on DCJTB exhibits a low turn-on voltage of 2.3 V and an extremely high maximum external quantum efficiency (EQE) of 9.3%. And the red phosphorescent device with the Ir(MDQ)2acac as the emitter realizes a maximum EQE of 20.3%. These remarkable results prove the feasibility of TADF exciplex systems simultaneously as the hosts of both high-performance fluorescent and phosphorescent red devices.