Efficient Ultra-Narrowband OLEDs Based on Carbazole-Fused Dual-Boron Embedded Multi-Resonance Thermally Activated Delayed Fluorescence Materials

The development of efficient multi-resonance thermally activated delayed fluorescence (MR-TADF) materials with ultra-narrowband emission presents an ongoing challenge. In this work, a carbazole-fused dual-boron embedded MR-TADF framework is proposed, achieving three emitters, CFDBO, CFDBA, and CFDBCz, via one-shot borylation with very high yields of over 70%. The emitters display ultra-narrowband blue emission with peaks ranging from 452 to 479 nm and small full width at half maximum (FWHM) values of only 16-18 nm in dilute toluene solutions. Furthermore, the organic light-emitting diode (OLED) incorporating CFDBO exhibits pure-blue emission with a peak of 460 nm and Commission International de l'Eclairage coordinates of (0.14, 0.12). Meanwhile, OLEDs incorporating CFDBA/CFDBCz demonstrate remarkable performances with high external quantum efficiencies of 30.9%/32.4% and exceptionally slender FWHM values of 21/22 nm, representing outstanding performances among reported MR-TADF materials. Utilizing a novel carbazole-fused dual-boron embedded multi-resonance thermally activated delayed fluorescence (MR-TADF) architecture, three emitters demonstrate ultra-narrowband emission ranging from pure-blue to cyan-green with full width at half maximums (FWHMs) of only 16-18 nm in dilute toluene. The corresponding organic light-emitting diodes (OLEDs) display high external quantum efficiencies (EQEs) of up to 32.4% and exceptionally slender FWHM values of 21/22 nm, representing outstanding performances among reported MR-TADF materials.image