A Multiresonant Thermally Activated Delayed Fluorescent Dendrimer with Intramolecular Energy Transfer: Application...

The development of narrowband emissive, bright, and stable solution-processed organic light-emitting diodes (SP-OLEDs) remains a challenge. Here, a strategy is presented that merges within a single emitter a TADF sensitizer responsible for exciton harvesting and an MR-TADF motif that provides bright and narrowband emission. This emitter design also shows strong resistance to aggregate formation and aggregation-cause quenching. It is based on a known MR-TADF emitter DtBuCzB with a donor-acceptor TADF moiety consisting of either tert-butylcarbazole donors (tBuCzCO₂HDCzB) or second-generation carbazole-based donor dendrons (2GtBuCzCO₂HDCzB) and a benzoate acceptor. The TADF moiety acts as an exciton harvesting antenna and transfers these excitons via Förster resonance energy transfer to the MR-TADF emissive core. The SP-OLEDs with 2GtBuCzCO₂HDCzB and tBuCzCO₂HDCzB thus show very high maximum external quantum efficiencies (EQE_max of 27.9 and 22.0%) and minimal efficiency roll-off out to 5000 cd m^-2.