Lone Pairs-Mediated Multiple Through-Space Interactions for Efficient Room-Temperature Phosphorescence

The simultaneous generation and stabilization of triplet excitons are the key to realizing efficient organic room temperature phosphorescence (RTP), which is challenging owing to the obscure mechanism and structure-property relationships. Herein, a strategy of lone-pair-mediated multiple through-space interactions (TSIs) is proposed to availably induce RTP. By incorporating heteroatoms to facilitate through-space n-n and n-π interactions, the lone pairs are delocalized throughout the structure, resulting in the dense splitting of the excited-state energy levels. Thus, more matched energy levels with a small energy gap between singlet and triplet states (Δ<i>E</i>_ST) emerge, resulting in multiple intersystem crossing (ISC) transition channels that assist triplet excitons generation. The strong TSIs also effectively rigidify the molecular structures and thus stabilize triplet excitons for radiation. Furthermore, the manipulation of TSI intensity allows efficiency enhancement, persistent time prolongation, and tolerance to high temperatures of RTP. This work not only explores the fundamental principle of the RTP mechanism from a new view but also provides a universal strategy for ISC promotion and triple excitons stabilization.