Spin manipulation in organic radicals

Organic luminescent radicals have attracted significant attention as efficient doublet emitters for organic light-emitting diodes (OLEDs) due to their distinctive and unique electronic and optical properties.Unlike conventional fluorescent, phosphorescent, and thermally activated delayed fluorescence (TADF)-based luminogens, radical materials with the open-shell structures facilitate the efficient emission originating from transition between the lowest doublet excited state and doublet ground state.This ability can address the transition problem associated with the triplet excitons, theoretically allowing an upper limit of 100% internal quantum efficiency (IQE) in purely organic radical molecules.Nonetheless, they generally exhibit lower photoluminescence quantum yields (PLQYs) and poor stability compared with the nonradical organic molecules.Therefore, quest for the development of the highly efficient radical emitters with high stability remains a highly desirable yet challenging task. ELECTROLUMINESCENCEIn 2015, Li et al. reported the use of a neutral π radical as the emitter in a radical OLED. 1 The organic π radical, known as (4-N-carbazolyl-2,6dichlorophenyl)bis(2,4,6-trichlorophenyl)methyl (TTM-1Cz), exhibited an open-Materials Cl Cl Cl Cl Cl Cl Cl Cl N Cl Cl Cl Cl Cl Cl Cl