Judicious Heteroatom Doping Produces High‐Performance Deep‐Blue/Near‐UV Multiresonant Thermally Activated Delayed Fluorescence OLEDs
Subeesh Madayanad Suresh, Le Zhang, Tomas Matulaitis, David Hall, Changfeng Si, Gaetano Ricci, Alexandra M. Z. Slawin, Stuart L. Warriner, David Beljonne, Yoann Olivier, Ifor D. W. Samuel, Eli Zysman‐Colman
Abstract
Abstract Two multiresonant thermally activated delayed fluorescence (MR‐TADF) emitters are presented and it is shown how further borylation of a deep‐blue MR‐TADF emitter, DIDOBNA‐N, both blueshifts and narrows the emission producing a new near‐UV MR‐TADF emitter, MesB‐DIDOBNA‐N, are shown. DIDOBNA‐N emits bright blue light (Φ PL = 444 nm, FWHM = 64 nm, Φ PL = 81%, τ d = 23 ms, 1.5 wt% in TSPO1). The deep‐blue organic light‐emitting diode (OLED) based on this twisted MR‐TADF compound shows a very high maximum external quantum efficiency (EQE max ) of 15.3% for a device with CIE y of 0.073. The fused planar MR‐TADF emitter, MesB‐DIDOBNA‐N shows efficient and narrowband near‐UV emission ( λ PL = 402 nm, FWHM = 19 nm, Φ PL = 74.7%, τ d = 133 ms, 1.5 wt% in TSPO1). The best OLED with MesB‐DIDOBNA‐N, doped in a co‐host, shows the highest efficiency reported for a near‐UV OLED at 16.2%. With a CIE y coordinate of 0.049, this device also shows the bluest EL reported for a MR‐TADF OLED to date.