ABSTRACT Aromaticity that is governed by Hückel's rule serves as a fundamental and underlaying concept in polycyclic aromatic hydrocarbons (PAHs). Multi‐resonance (MR) material belongs to a new class of heteroatom‐doped PAHs. In this work, we introduce anti‐Hückel aromatic pyrene unit in oxygen, boron, and nitrogen‐doped nanographene, namely OBN‐Pyr , resulting in an unexpected bathochromic shift in emission. Nucleus‐independent chemical shifts and anisotropies of the induced current density reveal the anti‐Hückel aromatic behavior plays a decisive role in the delocalization of HOMO/LUMO for OBN‐Pyr , hence lowering the energy gap; however, the incorporation of Hückel aromatic units leads to a hypsochromic shift in emission. OBN‐Pyr displays narrowband pure‐red emission at 628 nm, a full‐width at half‐maximum (FWHM) of 36 nm (0.11 eV), a high photoluminescence quantum yield of up to 94%, and a fast radiative decay rate of 1.0 × 10 8 s −1 in toluene. Highly efficient hyperphosphorescent (HP) OLEDs are achieved with a high maximum external quantum efficiency of 22.0%. The optimized HP‐OLEDs based on OBN‐Pyr result in pure‐red emission at 640 nm with an FWHM of 44 nm, corresponding to Commission Internationale de l'eclairage (CIE) coordinates of (0.70, 0.30), which are very close to the BT.2020 standard for red color.
Li et al. (Tue,) studied this question.