Highly efficient and persistent room temperature phosphorescence from cluster exciton enables ultrasensitive off-on VOC sensing

Summary

Room temperature phosphorescence (RTP) materials have attracted wide attention due to their application potential in sensing, data-encryption, bioimaging, and optoelectronic devices. However, improving RTP efficiency and lifetime simultaneously in metal-free systems remains the biggest challenge for realizing their applications. Herein, by exploiting long-lifetime triplets of naphthalene (NL) and intersystem crossing (ISC)-promoting factors from 1,4-dichlorobenzene (DCB), we unveil a guest/host system (NL/DCB) with concurrently high RTP quantum yield of >20% and ultralong lifetime of >760 ms (duration ∼10 s) at ambient conditions. Based on systematic experimental and theoretical investigations, the underlying mechanism for efficient RTP of NL/DCB is mainly elucidated to be the formation of cluster excitons that boost ISC and triplet population of NL molecules. Meanwhile, we showcase the first example of fast and ultrasensitive detection of a common hazardous VOC via turning on its ultralong afterglow by using NL/DCB RTP, opening another avenue for practical applications of purely organic phosphorescence.