Solution-Processable Pure-Red Multiple Resonance-induced Thermally Activated Delayed Fluorescence Emitter for Organic Light-Emitting Diode with External Quantum Efficiency over 20 %

Developing solution-processable red organic light-emitting diodes (OLEDs) with high color purity and efficiency based on multiple resonance thermally activated delayed fluorescence (MR-TADF) is a formidable challenge. Herein, by introducing auxiliary electron donor and acceptor moieties into the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distributed positions of multiple resonance skeleton simultaneously, an effective strategy to obtain red MR-TADF emitters was represented. The proof-of-the-concept molecule BN-R exhibits a narrowband pure-red emission at 624 nm, with a high luminous efficiency of 94 % and a narrow bandwidth of 46 nm. Notably, the fabricated solution-processable pure-red OLED based on BN-R exhibits a state-of-the-art external quantum efficiency over 20 % with the Commission Internationale de I'eclairage coordinates of (0.663, 0.337) and a long operational lifetime (LT50) of 1088 hours at an initial luminance of 1000 cd m(-2).

Automated summary

A solution-processable red OLED with high purity and efficiency was developed by introducing auxiliary donor and acceptor moieties into the HOMO and LUMO positions of the MR-TADF system. The molecule BN-R exhibited a narrowband pure-red emission at 624 nm, with a high luminous efficiency of 94% and a narrow bandwidth of 46 nm. The solution-processable pure-red OLED based on BN-R showed a state-of-the-art external quantum efficiency over 20% and a long operational lifetime of 1088 hours at an initial luminance of 1000 cd m(-2), with Commission Internationale de I'eclairage coordinates of (0.663, 0.337).