Lead-free Cs2SnX6 (X = Cl, Br, I) nanocrystals in mesoporous SiO2 with more stable emission from VIS to NIR light

Lead-free double-perovskite Cs 2 SnX 6 (X = Cl, Br, I) containing Sn 4+ is a more stable lead-free photovoltaic material than its homologue CsSnX 3 . However, its stability in air still affects its application. In this Letter, lead-free inorganic Cs 2 SnX 6 (X = Cl, Br, I) nanocrystals (NCs) were synthesized by a hot injection method and in-situ loaded into mesoporous SiO 2 . With the change of halogen content, the PL emission peak of pristine Cs 2 SnX 6 NCs were tuned from 430 nm to 780 nm covering the visible and near infrared spectrum region. Taking Cs 2 SnI 6 /SiO 2 NCs as an example, the optical property stability in solution is obviously improved, and it can be stored in air for over 2 h. Especially, the more stable NIR emission, non-toxicity and easy hydrolysis characteristics of Cs 2 SnX 6 /SiO 2 composite nanoparticles will have potential medical applications like photothermal and photodynamic therapies for cancers.