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

Abstract

Thermally activated delayed fluorescence (TADF) emitters based on multiple resonance (MR) effects are promising for high-definition organic light-emitting diodes (OLEDs) with narrowband emission and high efficiency. However, they still face the challenges of aggregation-caused quenching (ACQ) and spectral broadening. Solution-processable MR-TADF emitters with an external quantum efficiency (EQE) of >20% and a full width 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 a rigid B,N-containing polycyclic aromatic hydrocarbon core and four carbazole substituents as well as 12 tert-butyl groups on the periphery is designed. The multidimensional shielded effect largely limits the ACQ, intermolecular interactions, and spectral broadening. Consequently, solution-processed OLEDs based on 6TBN exhibit a maximum EQE of 23.0% and high color purity with a fwhm of 25 nm. Furthermore, the nondoped device achieves a high efficiency (12.3%) and merely a slight widening of the fwhm to 27 nm. This work provides a feasible strategy to achieve MR-TADF materials with resistance to concentration quenching and high color purity.

Efficient thermally activated delayed fluorophores featuring multi-donor arms and a π-extended acceptor core

“…7d and Table S4 (ESI†). Remarkably, our new TADF materials demonstrate state-of-the-art EQE values, 57–59 particularly in the long-wavelength region with EL peaks exceeding 550 nm. These results affirm the efficacy of our molecular design tactics in constructing highly efficient long-wavelength TADF emitters.…”

Acceptor modification of diindolocarbazole embedded multiple-resonance emitters for efficient narrowband deep-blue OLEDs with CIEy ≤ 0.08 and alleviated efficiency roll-off

“…[5][6][7][8][9][10][11][12][13] Recently, multiple-resonance (MR) organic emitters have emerged as promising candidates to overcome the drawbacks of conventional OLEDs driven by their efficient narrowband emission character. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] By integrating an opposite resonance effect of the electron-donating unit and the electronwithdrawing unit in a fused polycyclic framework, the MR effect could be triggered, which minimizes the bonding/antibonding character and suppresses the vibronic coupling between the ground (S 0 ) and the lowest excited singlet (S 1 ) states, giving rise to guaranteed sharpened spectra.…”

Recent endeavors and perspectives in developing solution-processable host materials for thermally activated delayed fluorescence organic light-emitting diodes

“…15–23 Solution processing is highly advantageous over vacuum processing owing to the easy processability and usage of low-cost instruments such as spin-coating, blade-casting, and inkjet printing in the former, while avoiding harsh fabrication conditions such as high temperature and pressure. Despite significant progress in the development of solution-processed OLEDs, 24–66 their efficiency and lifetimes still lag behind those of vacuum-processed devices.…”