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

Abstract

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/π‐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 π‐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).

Integrating the atomically separated frontier molecular orbital distribution of two multiple resonance frameworks through a single bond for high-efficiency narrowband emission

“…This viewpoint has been repeatedly verified in several subsequent studies. 32,33 These results provide a promising direction towards realizing ultranarrow band emissions of organic emitters, i.e. , to construct large fused MR frameworks integrating more doped B/N atoms with stronger atomic FMO distributions.…”

Narrowband Fluorescent Emitters Based on BN‐Doped Polycyclic Aromatic Hydrocarbons for Efficient and Stable Organic Light‐Emitting Diodes

“…also developed the first narrowband BODIPY‐based OLED matching the pure red standard defined by National Television Standards Committee (NTSC) with EQE of 18.3 % peaked at 623 nm. Recently, pioneered by Lee et al., [3a] a series of ICz derivatives with small FWHMs near 20 nm were constructed to fabricate narrowband OLEDs, but the emission peaks are mostly located at violet‐to‐blue region due to the neglectable charge‐transfer (CT) property [3b–g] . Duan et al.…”

Highly efficient multi-resonance thermally activated delayed fluorescence material toward a BT.2020 deep-blue emitter

“…In particular, π-extension has been effectively used to increase the reverse intersystem crossing rate constant (k RISC ), which is important for avoiding a severe efficiency roll-off at high voltage 30 . However, owing to the spectral redshift associated with πextension, a material with a high k RISC value and color purity adequate for a BT.2020 blue emitter has not been realized to date [41][42][43][44][45][46][47][48][49][50] .…”