Rational Multidimensional Shielded Multiple Resonance Emitter Suppresses Concentration Quenching and Spectral Broadening for Solution-Processed Organic Light-Emitting Diodes

Thermally activated delayed fluorescence (TADF) emittersbasedon multiple resonance (MR) effects are promising for high-definitionorganic light-emitting diodes (OLEDs) with narrowband emission andhigh efficiency. However, they still face the challenges of aggregation-causedquenching (ACQ) and spectral broadening. Solution-processable MR-TADFemitters with an external quantum efficiency (EQE) of >20% anda fullwidth at half-maximum (fwhm) of <30 nm have rarely been reported.To construct ACQ-resistant emitters without sacrificing color purity,the aggregation-induced MR-TADF material 6TBN with arigid B,N-containing polycyclic aromatic hydrocarbon core and fourcarbazole substituents as well as 12 tert-butyl groupson the periphery is designed. The multidimensional shielded effectlargely limits the ACQ, intermolecular interactions, and spectralbroadening. Consequently, solution-processed OLEDs based on 6TBN exhibit a maximum EQE of 23.0% and high color puritywith a fwhm of 25 nm. Furthermore, the nondoped device achieves ahigh efficiency (12.3%) and merely a slight widening of the fwhm to27 nm. This work provides a feasible strategy to achieve MR-TADF materialswith resistance to concentration quenching and high color purity.

Automated summary

In this study, an aggregation-induced MR-TADF material 6TBN was designed to overcome the challenges of concentration quenching and spectral broadening. The multidimensional shielded effect effectively limits aggregation and spectral broadening, leading to high color purity. OLEDs based on 6TBN showed high quantum efficiency and pure color emission. This work provides a feasible strategy to achieve MR-TADF materials with resistance to concentration quenching and high color purity.