Modulating Emission of Nonconventional Luminophores from Nonemissive to Fluorescence and Room-Temperature Phosphorescence via Dehydration-Induced Through-Space Conjugation

Processing nonconventional luminophores into ultralong room-temperature phosphorescence (RTP) materials with bright emission is extremely difficult but highly desired because of their intrinsic advantages together with the relatively weak spin-orbit coupling and rapid nonradiative decay in comparison to traditional aromatic compounds. Here, a straightforward heat treatment method was developed to promote the intersystem crossing efficiency and to suppress nonradiative pathways. A dehydration-induced through-space conjugation mechanism was proposed for explaining the activating of fluorescence and RTP of nonconventional luminophores. RTP materials with a phosphorescence quantum yield of 23.8% and emission lifetime of 1.3 s are developed. In addition, the emission color and lifetimes can be modulated by tuning the structure of ligands, which allows their applications in multilevel information encryption. These results open the door for designing highly efficient ultralong RTP materials, which also provides a clue to clarify the detailed emission profiles of RTP materials.

Automated summary

A heat treatment method was developed to enhance the intersystem crossing efficiency and suppress nonradiative pathways in nonconventional luminophores, leading to the activation of fluorescence and RTP. The phosphorescence quantum yield and emission lifetime of the RTP materials were significantly improved, with opportunities for applications in information encryption. This study provides insights into designing highly efficient ultralong RTP materials and understanding the emission profiles of RTP materials.