Achieving high-performance narrowband blue MR-TADF emitters by suppressing isomer formation and extending π-conjugate skeletons

Abstract

Multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters show great application potential in high color purity and high-resolution organic light-emitting diode (OLED) displays. However, high-performance narrowband blue emitters are still scarce. In this work, by introducing dibenzofuran and dibenzothiophene to extend π-conjugate skeletons, two blue MR-TADF emitters, namely Me-PABO and Me-PABS, were synthesized via a lithium-free direct borylation reaction, which showed large K_RISC values, high photoluminescence quantum yields (PLQYs) of 87.5% and 92.1%, and a small FWHM value of 21 nm, respectively. The electroluminescent devices employing Me-PABO and Me-PABS as emitters exhibited external quantum efficiencies (EQEs) of 20.4% and 23.0% and Commission Internationale de l’Eclairage (CIE) coordinates of (0.13, 0.09) and (0.12, 0.14), respectively. The work provided a viable strategy for the development of high-performance blue MR-TADF with narrow FWHM.