A Multiple Resonance Emitter Integrating Para-B-& pi;-B & PRIME;/Meta-N-& pi;-N Pattern via an Unembedded Organoboron Decoration for Both High-Efficiency Solution- and Vacuum-Processed OLEDs

Multiple resonance (MR)-type thermally activated delayed fluorescence (TADF) emitters have promising prospects for high-color-purity organic light-emitting diodes (OLEDs), but they are seldom attempted in the fabrication of solution-processed devices. In addition, another issue with MR-TADF emitters is that their heteroatom patterns are very limited, hampering their diversity. Herein, a novel double boron (B)-containing MR-TADF paradigm that merges an unembedded organoboron unit and a B-embedded & pi;-fused MR framework into one system, furnishing a unique para-B-& pi;-B & PRIME;/meta-N (nitrogen)-& pi;-N molecular pattern is proposed. Based on this, a proof-of-concept molecule, BNB & PRIME;-1, is developed, simultaneously achieving a bright sharp emission peaking at 540 nm with a full width at half maximum (FWHM) of only 24.5 nm/98 meV, a nearly unity photoluminescence quantum yield and excellent organic solubility. A solution-processed OLED using BNB & PRIME;-1 emitter delivers an impressive external quantum efficiency (EQE) as high as 36.2% with an emissive FWHM of only 30.0 nm/0.13 eV at & AP;540 nm; both parameters set new records among the ever-reported solution-processed MR-OLEDs. Moreover, BNB & PRIME;-1 also obtains a superhigh EQE of 40.3% in vacuum-processed OLEDs, surpassing all MR-OLEDs in the similar emission region. This work provides an interesting solution to develop high-performance solution-processable MR-TADF emitters with diverse heteroatom patterns.

Automated summary

A novel double boron-containing MR-TADF paradigm has been proposed, which achieves high-performance solution-processable OLEDs. The developed molecule exhibits a bright sharp emission peak, high photoluminescence quantum yield, and excellent organic solubility. This research has achieved impressive results in solution-processed devices.