Frontier Molecular Orbitals Regulation Enables Efficient and Ultraviolet to Deep-Blue Narrowband Emission

Modulating the emission wavelength in the range of ultraviolet to deep-blue with high color purity remains elusive. Herein, a versatile strategy is proposed from the perspective of rationally regulating nonbonding/pi-bonding character of frontier molecular orbitals to finely modulate emission colors while retaining superior color purity. By modifying the fused modes of indolo[3,2,1-jk]carbazole (ICz) units, the proof-of-the-concept emitters emphasize adjustable hybridization of nonbonding and pi-bonding characteristics, achieving a wide-range color tuning range from ultraviolet (380 nm) to deep-blue (428 nm) and small full-width at half-maximum (FWHM) of 8-33 nm (63-222 meV). Organic light-emitting diodes based on the new emitter exhibit electroluminescence emission at 430 nm, a small FWHM of 44 nm (253 meV), maximum external quantum efficiency of 10.9%, and CIE color coordinates of (0.16, 0.05). The CIE coordinates are close to the National Television System Committee (NTSC) standard blue of (0.15, 0.06).