Narrowband Organic Afterglow Materials Exhibiting 11.2 nm FWHM, 38% Phosphorescence Efficiency and 1.5 s Emission Lifetime Under Ambient Conditions

Abstract

Abstract Narrowband organic room‐temperature phosphorescence (RTP) remains rare due to significant high‐frequency vibronic coupling in T 1 →S 0 electronic transition, where T 1 and S 0 represent the lowest triplet excited state and ground state, respectively. Here, we report coronene‐derived ( CoDe ) luminophores exhibiting ultra‐narrowband RTP (full width at half maximum FWHM = 11.2 nm) with a 1.5 s lifetime and 38% afterglow efficiency in a phenyl benzoate (PhB) matrix. The narrow emission arises from enhanced coupling with low‐frequency vibrational modes in localized excitation (LE) states, as supported by vibronic simulations. Under high‐power excitation, the CoDe ‐PhB further exhibits organic long‐persistent luminescence (OLPL) lasting over 40 min (FWHM = 14.7 nm), governed by a two‐photon ionization‐induced charge‐separation mechanism. The materials are processable via melt‐casting and excitable by ambient or white light, offering practical utility for high‐color‐purity afterglow display and lighting applications. This work establishes low‐frequency vibronic engineering as a new route to narrowband RTP and OLPL emitters beyond conventional multi‐resonance‐based designs.