Exciton dynamics of an aggregation-induced delayed fluorescence emitter in non-doped OLEDs and its application as host for high-efficiency red phosphorescent OLEDs

Aggregation-induced delayed fluorescence (AIDF) materials have great potential in non-doped OLEDs due to their high photoluminescence (PL) quantum efficiency in film, high exciton utilization in the aggregated state and negligible efficiency roll-off at high luminance. However, their efficient mechanism in OLEDs is not yet well understood. Here, the exciton dynamics are used to investigate the electroluminescence (EL) mechanism of an AIDF emitter (4-(10H-phenoxazin-10-yl)phenyl)-(9-phenyl-9H-carbazol-3-yl)methanone (CP-BP-PXZ) in detail. It can be seen that the high efficiency and negligible efficiency roll-off in non-doped OLEDs based on CP-BP-PXZ as the emitter are ascribed to the effective reverse intersystem crossing (RISC) from high level triplet T2 to singlet S1 in the aggregated state. Furthermore, CP-BP-PXZ also exhibits excellent properties as a phosphor host due to its good AIDF properties. Thus, high-efficiency red phosphorescent OLEDs with low roll-off efficiency are successfully fabricated based on CP-BP-PXZ as the host. The maximum external quantum efficiency (EQEmax) reaches 23% and is maintained at 21% at a luminance of 1000 cd m-2. Investigation of the low efficiency roll-off of AIDF non-doped OLEDs from the perspective of device physics and AIDF application in PHOLEDs.

Automated summary

Aggregation-induced delayed fluorescence (AIDF) materials have high quantum efficiency and efficient exciton utilization in non-doped OLEDs. This study investigates the electroluminescence (EL) mechanism of an AIDF emitter in detail and successfully fabricates high-efficiency red phosphorescent OLEDs based on it. The research provides insights into the low efficiency roll-off of AIDF non-doped OLEDs and their application in PHOLEDs.