Pressure-Induced Local Excitation Promotion: New Route toward High-Efficiency Aggregate Emission Based on Multimer Excited State Modulation

Achieving
high-efficiency solid state emission is essential for
practical applications of organic luminescent materials. However,
intermolecular interactions generally induce formation of multimeric
aggregate excited states with deficient emissive ability, making it
extremely challenging to enhance emission in aggregated states. Here
we demonstrate a novel strategy of continuously regulating multimeric
excitation constituents with a high-pressure technique successfully
enhancing the emission in a representative organic charge-transfer
material, Laurdan (6-lauroyl-N,N-dimethyl-2-naphthylamine). The Laurdan crystal exhibits distinct
emission enhancement up to 4.1 GPa accompanied by a shift in the emission
color from blue to cyan. Under compression, the π–π
interplanar distance in Laurdan multimers is reduced, and intermolecular
wave function diffusion is demonstrated to be improved simultaneously,
which results in local excitation promotion and thus enhanced emission.
Our findings not only provide new insights into multimeric excited
state emission modulation but also pave the way for the further design
of high-performance aggregated luminophores.