The Combination of a Donor-Acceptor TADF and a MR-TADF Emitting Core Results in Outstanding Electroluminescence Performance.
basic_science · Level V
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- Record sourced from PubMed, PMID 39394825.
- Also identified by DOI 10.1002/adma.202412761 and PMC identifier 11635906.
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Abstract
Here the utility and potential of an emitter design are demonstrated, consisting of a narrowband-emitting multiresonant thermally activated delayed fluorescent (MR-TADF) core that is decorated with a suitably higher energy donor-acceptor TADF moiety. Not only does this D-A TADF group offer additional channels for triplet exciton harvesting and confers faster reverse intersystem crossing (RISC) kinetics but it also acts as a steric shield, insulating the emissive MR-TADF core from aggregation-caused quenching. Two emitters, DtCzBN-CNBT1 and DtCzBN-CNBT2, demonstrate enhanced photophysical properties leading to outstanding performance of the organic light-emitting diodes (OLEDs). DtCzBN-CNBT2, containing a D-A TADF moiety, has a faster k<sub>RISC</sub> (1.1 × 10<sup>5</sup> s<sup>-1</sup>) and higher photoluminescence quantum yield (Φ<sub>PL</sub>: 97%) compared to DtCzBN-CNBT1 (0.2 × 10<sup>5</sup> s<sup>-1</sup>, Φ<sub>PL</sub>: 90%), which contains a D-A moiety that itself is not TADF. The sensitizer-free OLEDs with DtCzBN-CNBT2 achieve a record-high maximum external quantum efficiency (EQE<sub>max</sub>) of 40.2% and showed milder efficiency roll-off (EQE<sub>1000</sub> of 20.7%) compared to the DtCzBN-CNBT1-based devices (EQE<sub>max</sub> of 37.1% and EQE<sub>1000</sub> of 11.9%).