Aggregation-Induced Dual-Phosphorescence from Organic Molecules for Nondoped Light-Emitting Diodes

Aggregation-induced emission (AIE) is a beneficial strategy for generating highly effective solid-state molecular luminescence without suffering losses in quantum yield. However, the majority of reported AIE-active molecules exhibit only strong fluorescence, which is not ideal for electrical excitation in organic light-emitting diodes (OLEDs). By introducing various substituent groups onto the biscarbazole compound, a series of molecular materials with aggregation-induced phosphorescence (AIP) is designed, which exhibits two distinctly different phosphorescence bands and an absolute solid-state room-temperature phosphorescence quantum yield up to 64%. Taking advantage of the AIE feature, the AIP molecules are fabricated into OLEDs as a homogeneous light-emitting layer, which allows for relatively small efficiency roll-off and shows an external electroluminescence quantum yield of up to 5.8%, more than the theoretical limit for purely fluorescent OLED devices. The design showcases a promising strategy for the production of cost-effective and highly efficient OLED technology.