ABSTRACT Developing purely organic emitters capable of delivering efficient electroluminescence beyond 800 nm remains a central challenge due to severe non‐radiative losses governed by the energy‐gap law and strong exciton–vibration coupling. Herein, we report a molecularly engineered luminescent radical, TTM‐DPS, synthesized by incorporating N,N‐diphenylthiophen‐2‐amine (DPS) into the tris(2,4,6‐trichlorophenyl)methyl (TTM) radical. This donor‐acceptor arrangement enhances long‐range charge‐transfer coupling while preserving a non‐bonding hole‐electron distribution in the D 1 doublet state, effectively suppressing high‐frequency vibrational modes that typically trigger non‐radiative decay. As a result, TTM‐DPS exhibits deep‐NIR photoluminescence with a peak at 895 nm and a fourfold enhanced quantum yield (4%) relative to the fused donor analogue TTM‐2PTI (2PTI, 4‐phenyl‐4H‐thieno3,2‐bindole). When incorporated into OLEDs, TTM‐DPS enables deep‐NIR emission at 883–908 nm, achieving an external quantum efficiency of 1.26% and a radiance of 25800 mW sr −1 m −2 , ranking among the best metal‐free emitters operating in this spectral region. This work establishes a generalizable donor‐engineering strategy to mitigate exciton‐vibration coupling in radical systems, offering a promising pathway toward next‐generation high‐efficiency deep‐NIR optoelectronics.
Ding et al. (Thu,) studied this question.