Insight into the synthesis of colloidal cesium tin halide perovskite nanocrystals: size, shape control and phase transition.

Colloidal nanocrystals (NCs) of fully inorganic perovskites have attracted much attention for their wide optoelectronic applications. Cesium tin halide (CsSnX₃, X= Cl, Br, I) NCs possess the advantage of environmental friendliness. While there have been some reports on the synthesis of CsSnX₃NCs, the systematic study on turning the size and morphology through reaction temperature and surface ligands is lacking. In this report, CsSnX₃NCs were synthesized using a hot injection method with three precursors for Cs, Sn and X sources, respectively. We systematically altered the reaction temperature and ligands concentration to investigate their influence on the NC products. Upon decreasing the reaction temperature from 180 °C to 90 °C, the photoluminescence peak underwent a blue shift from 869 nm to 847 nm. Nanorods with a diameter as low as 3 nm were achieved at a lower reaction temperature, while cubic NCs with a size of 15 nm were achieved at the higher reaction temperature. The NCs show an increasing size and a wider distribution with the concentration of oleic acid and oleylamine (OAm) increasing. However, hexagonal Cs₄SnI₆NCs other than CsSnI₃NCs will be produced when the OAm concentration is larger than 0.4 M. The study shed a light on the controllable synthesis of Sn-based perovskite NCs.