A Highly Twisted Carbazole‐Fused DABNA Derivative as an Orange‐Red TADF Emitter for OLEDs with Nearly 40 % EQE

Abstract

Multiple resonance (MR) type thermally activated delayed fluorescence (TADF) material is currently a research hotspot in organic light‐emitting diodes (OLEDs) due to their high color purity and high exciton utilization. However, there are only a handful of MR‐TADF emitters with emissions beyond the blue‐to‐green region. The very limited emission colors for MR‐TADF emitters are mainly caused by the fact that so far molecular modifications of MR‐TADF do not offer much change in the emission colors. Here, we report a new approach to modifying a prototypical MR core of DABNA by fusing carbazoles to the MR framework. The carbazole‐fused molecule (TCZ‐F‐DABNA) basically maintains the MR‐dominated features of DABNA while red‐shifting the emission. Its OLED achieves an external quantum efficiency of 39.2 % with a peak at 588 nm, which is a record‐high efficiency for OLEDs with peaks beyond 560 nm. This work provides a new approach for significantly tunning emission colors of MR‐TADF emitters.

Peripheral engineering of platinum(ii) dicarbene pincer complexes for efficient blue hyperphosphorescent organic light-emitting diodes

“…7,8 Multi-resonant thermally activated delayed fluorescent (MR-TADF) molecules have become the most intensively researched topics due to their merits including fast radiative decay, [9][10][11] narrow full width at half maximum (FWHM), proneness to adapt horizontal alignment and high luminescent efficiency. 12,13 Thus, MR-TADF molecules possess great potential to improve external quantum efficiency (EQE) towards 40% with color purity comparable to quantum dot LEDs, [14][15][16][17] simultaneously. Another type of promising emitter is an N-heterocyclic carbene (C^C NHC ) coordinated iridium(III) complex (Ir(C^C NHC ) 3 ), 18 a representative emitter of which, i.e., mer-Ir(CF 3 pbp) 3 , has delivered an EQE max of 21.2% with Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.05), 19 showing performances comparable to the state-of-the-art TADF emitters.…”

A comparative study of two multi-resonance TADF analogous materials integrating chalcogen atoms of different periods

“…The higher optimized concentration of BNCzPTZ can be ascribed to its structure with greater torsion, which may help to suppress intermolecular close packing and relieve concentration quenching with increasing doping levels. 38 As shown in Fig. 4(c), the efficiency behavior of the BNCzPXZ based device is inferior to that of the BNCzPTZ based one.…”

Recent advances in highly-efficient near infrared OLED emitters

“…For example, Zhang et al 125 have designed a highly twisted carbazole-fused DABNA derivative that displays Z ext up to 39% with l EL at 588 nm. The highly twisted structure helped to relieve concentration quenching, allowing the development of devices with doping ratio as high as 8%, unusual for this class of materials.…”