Pyridine‐dicarbonitriles acceptor engineering in multi‐resonance thermally activated delayed fluorescence with hybridized short‐ and long‐range charge transfer for high‐performance electroluminescence

Abstract

Multi‐resonance (MR) thermally activated delayed fluorescence (TADF) materials exhibit narrowband emission and high efficiency, making them attractive for application in organic light‐emitting diodes (OLEDs). However, compared with conventional donor‐acceptor (D‐A) type TADF emitters, MR‐TADF molecules typically suffer from relatively large singlet‐triplet energy gaps (Δ E _ST ) and slow reverse intersystem crossing (RISC) rates ( k _RISC ), highlighting the need for further research to overcome these limitations. In this work, a novel MR‐TADF molecule, BNPCN, is designed through integrating an electron‐withdrawing block (pyridine‐dicarbonitriles) into a classic MR emitter framework (DtBuCzB). The configuration synergistically couples intramolecular short‐range charge transfer and long‐range charge transfer within a single architecture. As a result, a narrow green emission bandwidth centered at 537 nm with a full width at half maximum of 47 nm is maintained, while Δ E _ST is minimized to 0.02 eV and the k _RISC is accelerated to 3.6 × 10 ⁶  s ⁻¹ . Successively, BNPCN‐based OLED achieves an external quantum efficiency of up to 32.11%, maximum luminance ( L _max ) as high as 29,368 cd m ⁻² , with Commission Internationale de l'Éclairage (CIE) coordinates of (0.296, 0.587).