A Multiresonant Thermally Activated Delayed Fluorescent Dendrimer with Intramolecular Energy Transfer: Application for Efficient Host‐Free Green Solution‐Processed Organic Light‐emitting Diodes

Abstract 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 ( tBuCzCO 2 HDCzB ) or second‐generation carbazole‐based donor dendrons ( 2GtBuCzCO 2 HDCzB ) 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 2GtBuCzCO 2 HDCzB and tBuCzCO 2 HDCzB 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 .