Abstract: Stable organic luminescent radicals have emerged as a distinctive class of functional emitters owing to their unconventional electronic structures and spin-allowed radiative transitions, thereby enabling promising opportunities for optoelectronics, spin-related photonics, and quantum technologies. However, severe aggregation-caused quenching (ACQ) in the condensed state—driven by intensified intermolecular interactions and enhanced nonradiative deactivation—remains a major obstacle to practical implementation. Moving beyond low-loading physical doping strategies, recent advances increasingly emphasize molecular-level chemical regulation as a fundamental approach to address ACQ. Two effective directions have emerged: (i) constructing radical polymers to spatially isolate spin centers by creating protective microenvironments, and (ii) precision molecular design to tailor steric profiles and packing motifs, thereby modulating intermolecular coupling and suppressing nonradiative loss. This review summarizes the condensed-state photophysical behaviors of organic luminescent radicals, mechanistic insights into ACQ suppression and emission regulation, as well as key design principles across molecular, polymeric, and hybrid radical systems. Remaining challenges and emerging opportunities in bioimaging, optoelectronic devices, and quantum or spin-enabled applications are also discussed to facilitate the translation from fundamental studies toward practical platforms.

Key words: Luminescent radical, Condensed-state luminescence, Aggregation-caused quenching, Radical polymer, Molecular structure design