Spin-Enhanced Reverse Intersystem Crossing andElectroluminescence in Copper Acetate-Doped Thermally ActivatedDelayed Fluorescence Material br

Thermally activated delayedfluorescence (TADF) materials are attractive fornext-generation organic light-emitting diodes (OLEDs) because of their utilization ofnonradiative triplets via reverse intersystem crossing (RISC), which requires not only a smallsinglet-triplet energy splitting but also the conservation of spin angular momentum. Here weuse copper acetate as a spin sensitizer to facilitate RISC and thus enhance electroluminescencein TADF-exciplex OLEDs. Copper acetate is involved in the radiative decay process due to itscoordination interaction with exciplex molecules having intermolecular charge-transfercharacteristics, which causes significant changes in the photoluminescence intensity andlifetime. Meanwhile, magneto-photoluminescence reveals that the addition of copper acetatepromotes spin conversion in the RISC process. It allows the enhancement of theelectroluminescence (similar to 80%) from spin-sensitized OLEDs, accompanied by the suppressionof magneto-electroluminescence upon the doping of copper acetate. These results illustratethat using a spin sensitizer may overcome the limitation of harvesting nonradiative triplets inorganic luminescent materials and devices.