Pure Hydrocarbon Emitter with 6 nm FWHM

High-purity emitters with an ultranarrow-band emission are a critical requirement for next-generation displays and lighting, yet it remains a formidable challenge for purely organic materials, particularly in the ultraviolet region. Herein, a general molecular design strategy based on the "stereo-lock" concept, represented by diarylbenzene derivatives solely from carbon and hydrogen, is presented. This strategy effectively suppresses intramolecular C-C/C-H stretching and attenuates vibronic coupling via intramolecular through-space interactions between two aryl groups, yielding a record full width at half maximum (FWHM) of merely 6 nm at 80 K from a single molecule. In the solid state, their aggregates with intermolecular positive exciton coupling induce quantum interference that selectively quenches the v0-0 transition, resulting in an ultranarrow FWHM of 17 nm at room temperature. Leveraging this synergy, diarylbenzene-based OLED devices with pure ultraviolet electroluminescence with an 18 nm FWHM and a CIE coordinate of (0.165, 0.022) are achieved. This stereo-lock architecture circumvents the fundamental limitation of vibronic coupling in pure hydrocarbons and addresses the absence of high-color-purity ultraviolet OLEDs, establishing a powerful and versatile design paradigm for narrowband emitters.