Exciton harvesting of dual-emitting room temperature organic phosphors using a thermally activated delayed fluorescence sensitizer

Efficiency improvement of dual-emitting room-temperature phosphorescent (RTPH) organic light-emitting diodes (OLEDs) was studied by employing a device approach of sensitizing the RTPH emission using a thermally activated delayed fluorescence (TADF) sensitizer by energy transfer mechanism. The RTPH material was (10-phenyl-10H-phenoselenazine-3,7-diyl)bis(phenylmethanone) (PSeBBz) which emits at 505 nm by TADF and 563 nm by phosphorescence. The luminance and maximum external quantum efficiency of the PSeBBz device were enhanced by about 4.0 times and 1.7 times by the TADF sensitizing approach, respectively. Transient photoluminescence and transient electroluminescence measurements revealed that the long-time scale emission components of the dual-emitting RTPH material by triplet excitons were enhanced, indicating that exciton population was increased by sensitized Förster energy transfer and reduced triplet exciton quenching process such as triplet-triplet annihilation and triplet-polaron annihilation. • Efficiency enhancement of dual-emitting room-temperature phosphorescent organic light-emitting diode. • Phosphor sensitization using thermally activated delayed fluorescence materials. • Reduced triplet exciton quenching mechanisms using sensitizing device approach.