Ultrabroad NIR emission from paired [SbCl4]− clusters in hybrid antimony chlorides

Abstract

Ultrabroad near-infrared (NIR) luminescent materials are essential for next-generation technologies in bioimaging, night vision, and medical diagnostics. Here, a new family of six ASbCl₄-type hybrid metal halides is reported, which exhibit highly tunable and exceptionally broad NIR emission. By tailoring the organic A-site cations, their emission maxima are tuned from 855 to 1114 nm, with a record bandwidth of 415 nm. At low temperatures, the red emission at 620 nm is attributed to triplet self-trapped excitons (STEs) in single [SbCl₄]⁻ units, whereas at higher temperatures, strong electron–phonon coupling stabilizes bipolaronic states in paired [SbCl₄]⁻ disphenoids, giving rise to ultrabroad emission extending to 1600 nm. These results highlight bipolaronic emission as a powerful design principle for achieving long-wavelength and broadband NIR luminescence, opening new avenues for advanced optoelectronic and biomedical applications.