Lone pairs-mediated multiple through-space interactions for efficient room-temperature phosphorescence

The generation and stabilization of triplet excitons is the key to realize efficient organic room temperature phosphorescence (RTP), which is challenging owing to the obscure mechanism and structure-property relationships. Herein, a strategy of lone pairs-mediated multiple through-space interactions is proposed to availably induce RTP. By introducing through-space nn and n interactions by dint of heteroatoms, the lone pairs are delocalized within the structure, causing dense excited-state energy level splitting. Thus, more matched energy levels with small energy gap between singlet and triplet states appear, resulting in multiple ISC transition channels which assist triplet excitons generation. The strong TSIs also effectively rigidify the molecular structures and thus stabilize generated triplet excitons for radiation. Furthermore, the manipulation of TSIs intensity allows efficiency enhancement, lifetime prolongation, and tolerance to high temperature of RTP. This work not only explores the fundamental principle of RTP mechanism from a new view, but also provides a universal strategy for ISC promotion and triple excitons stabilization.