Efficient Narrowband Electroluminescence at ∼380 nm via Acceptor-Engineered Ultraviolet Hybridized Localized and Charge Transfer Fluorophores with Aggregation-Enhanced Emission

Developing efficient ultraviolet (UV) organic light-emitting diodes (OLEDs) with narrowband emission approaching 380 nm remains an important and challenging issue despite their promising applications in biology, chemistry, industry, and healthcare. Herein, two donor–acceptor (D–A) type aggregation-enhanced emission (AEE) active emitters 3,6PC9N and 3,6PC9D, featuring hybridized localized and charge transfer states, are developed by connecting small-sized acceptors (cyanobenzene or pyrimidine) to a three-dimensional rigid and bulky carbazolyl donor, where the molecular packing modes are manipulated precisely. The resulting doped OLEDs demonstrate significant narrow UV light with peaks of 384 and 379 nm, full width at half maximum values of 36 nm, and impressive external quantum efficiencies (EQEs) of 7.39% and 7.18%, respectively. Owing to the “spread-open” conformation and weak π–π packing interactions in 3,6PC9N, its nondoped device exhibits a higher EQE of 4.17%, and color coordinates of (0.162, 0.035). This work offers an effective approach to high-performance UV emitters featuring short-wavelength narrowband electroluminescence.