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

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 , 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.