Non‐Benzenoid π‐Electronic Perturbation Enables Frontier‐Orbital Symmetry Reconstruction in Ultra‐Narrowband Organic Luminophores

ABSTRACT Organic luminophores with ultra‐narrow full widths at half‐maximum (FWHMs) are highly demanding for high‐definition displays; however, the current strategies, including bond‐length homogenization and multiple‐resonance effects, often suffer from limited molecular design flexibility. Herein, we present a new series of ultra‐narrow organic luminophores by incorporating an antiaromatic cyclobutadiene motif into nitrogen‐containing polycyclic aromatic hydrocarbons. Theoretical simulations show that the fused four‐membered rings introduce a non‐benzenoid π‐electronic perturbation, which reconstructs the frontier‐orbital symmetry. This reconstruction suppresses intrinsic bonding‐antibonding transition character, affording an exceptionally narrow FWHM of 10.3 nm (in dilute toluene) and a near‐unity photoluminescence quantum yield (PLQY ≈ 100%). In addition, weak‐aromaticity‐mediated two‐dimensional (2D) π‐conjugation extension not only enhances luminescence efficiency but also affords sufficient chemical robustness compatible with vacuum evaporation process. Organic electroluminescent (EL) devices incorporating these CBD‐embedded emitters exhibit high performance, with a maximum current efficiency surpassing 30.0 cd A − 1 , an external quantum efficiency exceeding 20.1%, and minimal efficiency roll‐off, thereby underscoring the substantial potential of antiaromaticity modulation for the development of cutting‐edge narrowband emitters.