Nonbonding/Bonding Molecular Orbital Regulation of Nitrogen‐Boron‐Oxygen‐embedded Blue/Green Multiresonant TADF Emitters with High Efficiency and Color Purity

Abstract In this study, we synthesized and characterized multiresonant thermally activated delayed fluorescent (TADF) materials embedded with nitrogen‐boron‐oxygen (N−B−O), exhibiting color‐tunability between blue and green, namely NBO , m‐DiNBO , and p‐DiNBO . The three emitter materials showed a high photoluminescence quantum yield (PLQY) and a state‐of‐the‐art narrow full width at half maximum (FWHM) of 96 %/25 nm, 87 %/17 nm, and 99 %/19 nm, respectively. For m‐DiNBO and p‐DiNBO , the emission color could be tuned from blue to green by regulating the nonbonding/bonding molecular orbital characters. Owing to the expanded planar molecular structure, m‐DiNBO and p‐DiNBO showed high horizontal dipole ratio (Θ) of 88 % and 92 %, respectively. OLEDs were prepared with NBO , m‐DiNBO , and p‐DiNBO , exhibiting high external quantum efficiencies of 16.8 %, 24.2 %, and 21.6 %, respectively. NBO and m‐DiNBO exhibited pure‐blue emission with CIE coordinates of (0.137, 0.142) and (0.126, 0.098), respectively. p‐DiNBO showed pure‐green emission with a CIE coordinate of (0.258, 0.665).