A direct observation of up-converted room-temperature phosphorescence in an anti-Kasha dopant-matrix system.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37031245.
- Also identified by DOI 10.1038/s41467-023-37662-y and PMC identifier 10082826.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
It is common sense that emission maxima of phosphorescence spectra (λ<sub>P</sub>) are longer than those of fluorescence spectra (λ<sub>F</sub>). Here we report a serendipitous finding of up-converted room-temperature phosphorescence (RTP) with λ<sub>P</sub> < λ<sub>F</sub> and phosphorescence lifetime > 0.1 s upon doping benzophenone-containing difluoroboron β-diketonate (BPBF<sub>2</sub>) into phenyl benzoate matrices. The up-converted RTP is originated from BPBF<sub>2</sub>'s T<sub>n</sub> (n ≥ 2) states which show typical <sup>3</sup>n-π* characters from benzophenone moieties. Detailed studies reveal that, upon intersystem crossing from BPBF<sub>2</sub>'s S<sub>1</sub> states of charge transfer characters, the resultant T<sub>1</sub> and T<sub>n</sub> states build T<sub>1</sub>-to-T<sub>n</sub> equilibrium. Because of their <sup>3</sup>n-π* characters, the T<sub>n</sub> states possess large phosphorescence rates that can strongly compete RTP(T<sub>1</sub>) to directly emit RTP(T<sub>n</sub>) which violates Kasha's rule. The direct observation of up-converted RTP provides deep understanding of triplet excited state dynamics and opens an intriguing pathway to devise visible-light-excitable deep-blue afterglow emitters, as well as stimuli-responsive afterglow materials.