Regioisomeric effects of dibenzofuran on the properties of boron-nitrogen multiple resonance emissive materials

Multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters have immense potential for use in the development of high color purity and high-resolution organic light-emitting diode (OLED) displays. However, the scarcity of high-performance narrowband blue emitters has been a challenge. Herein, three blue MR-TADF emitters have been synthesized using halogen borylation. The introduction of dibenzofuran to extend the pi-conjugate skeletons has resulted in emitters with exceptional properties such as large reverse intersystem crossing (RISC) rates, a high photoluminescence quantum yield (PLQY) of 92% and a small full width at half maximum (FWHM) value of 25 nm. The electroluminescent devices utilizing DABNA-3-DBF as emitters have displayed remarkable external quantum efficiencies (EQEs) of 25.9% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.16, 0.07). This work presents a viable strategy for the development of high-performance blue MR-TADF with a narrow FWHM. Regioisomeric effects have a profound impact on the OLED efficiency. DABNA-3-DBF demonstrated enhanced PLQY and a EQEmax of 25.9%, showcasing optimized conjugation for greater performance.