Stable Thermally Activated Delayed Fluorescence?Sensitized Red Fluorescent Devices through Physical Suppression of Dexter Energy Transfer

To date, thermally activated delayed fluorescence-sensitized fluorescent organic light-emitting diodes (TSF-OLEDs) have undergone substantial research to achieve high efficiency and good operational stability in wide color gamut regions. Usually, a highly efficient TSF device, the Förster resonance energy transfer rate (kFRET) should be enhanced, whereas Dexter (kDET) suppressed. Even though devices are achieved all RGB regions by satisfying BT2020 requirements, achieving long device lifetimes is still challenging. Herein, stable red-TSF reported adopting new suppressive layer (DSL) adjacent main emissive layer. Here, DSL can improve distance between excitons generated from host-TADF final dopant (FD) of which allows for suppressing kDET. Furthermore, detailed mechanistic pathways analyzed varying doping concentration with different thicknesses positions. Among fabricated devices, DSL-TSF manifested longer lifetime (LT95) over 370 h at 5000 cd m-2 reduced roll-off compared devices. Such OLEDs owing decreased kDET than