Organic NIR Afterglow with Emission Wavelengths Beyond 800 nm
Organic near-infrared (NIR) afterglow materials hold potential for bioimaging due to deep tissue penetration and high signal-to-background ratio (SBR). However, achieving emission wavelengths above 800 nm remains a significant challenge because of the energy gap law, which accelerates nonradiative decays and destabilizes triplet excitons. Here, bright NIR afterglow at 820 nm is realized via a molecular design strategy: alternating donor-acceptor (D-A) structures and multiple S···O intramolecular interactions enhance intramolecular charge transfer (ICT) and strengthen intramolecular interactions. Terminal groups and side chains optimize intermolecular interactions to suppress nonradiative transitions. The resulting material exhibits afterglow with a wavelength of 820 nm, surpassing previous organic afterglow systems limited to 780 nm. This work provides a promising strategy for efficient NIR afterglow, promoting applications in deep-tissue bioimaging with high SBR. The findings address the bottleneck of extending afterglow wavelengths beyond 800 nm, offering a viable route for advanced bioimaging and anticounterfeiting technologies.