Boron‐ and Oxygen‐Doped π‐Extended Nanographene: An Emitting Material for Organic Light‐Emitting Diodes

Expanding the molecular framework of hexabenzo[ a,c,fg,j,l,op ]tetracene (HBT) via heteroatom incorporation and topological edge control is crucial for achieving desired photophysical properties. However, synthesizing heteroatom‐doped HBT derivatives remains highly challenging, and effective molecular design strategies have not yet been established. Herein, the synthesis of boron (B)‐ and oxygen (O)‐doped expanded HBT ( BO‐HBT ) is carried using a sequential Scholl cyclization strategy. This work is the first example of a B/O‐expanded HBT molecule, demonstrating that heteroatom incorporation and peripheral alkyl group modifications enable accurate tuning of its electronic structure and photonic properties. Consequently, BO‐HBT exhibits a reduced bandgap (2.55 eV), robust electrochemical stability, a horizontal emitting dipole orientation ratio of 88%, and a high photoluminescence quantum yield of 62.8% in toluene. Density functional theory calculations further elucidate its fluorescence mechanism, revealing that all the frontier orbitals of BO‐HBT are predominantly localized in the central pyrene and boron‐containing parts and the peripheral biphenyl moieties play a minor role. Hence, the redox and photoluminescence properties of BO‐HBT closely resemble those of BO‐BPP , a structurally related B/O‐fused pyrene system. Notably, BO‐HBT demonstrated promising performance as an emitting dopant material in organic light‐emitting diodes (OLEDs), achieving an external quantum efficiency of up to 6.2% in the pure green visible region and exceeding 10% in hyperfluorescent devices. These results represent the first successful demonstration of an HBT derivative as an emissive dopant in OLEDs and underscore BO‐HBT's potential for advanced optoelectronic applications.