Highly efficient and stable thermally activated delayed fluorescent palladium(II) complexes for organic light-emitting diodes.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37315147.
- Also identified by DOI 10.1126/sciadv.adh0198 and PMC identifier 10266720.
- Licence recorded as CC BY-NC.
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Abstract
Transition metal complexes exhibiting thermally activated delayed fluorescence (TADF) remain underdeveloped for organic light-emitting diodes (OLEDs). Here, we describe a design of TADF Pd(II) complexes featuring metal-perturbed intraligand charge-transfer excited states. Two orange- and red-emitting complexes with efficiencies of 82 and 89% and lifetimes of 2.19 and 0.97 μs have been developed. Combined transient spectroscopic and theoretical studies on one complex reveal a metal-perturbed fast intersystem crossing process. OLEDs using the Pd(II) complexes show maximum external quantum efficiencies of 27.5 to 31.4% and small roll-offs down to 1% at 1000 cd m<sup>-2</sup>. Moreover, the Pd(II) complexes show exceptional operational stability with LT<sub>95</sub> values over 220 hours at 1000 cd m<sup>-2</sup>, benefiting from the use of strong σ-donating ligands and the presence of multiple intramolecular noncovalent interactions beside their short emission lifetimes. This study demonstrates a promising approach for developing efficient and robust luminescent complexes without using the third-row transition metals.