Formation and Stability of Cs2SnBr6 Perovskite Nanocrystals from CsSn2Br5 Nanocubes

Lead-free Sn(II) based, CsSn2Br5, perovskite nanocubes were synthesized using a modified hot-injection method by tuning the injection temperature and reaction conditions. The formation of Sn(IV) based, Cs2SnBr6, perovskite nanocrystals (PNCs) from CsSn2Br5 perovskite nanocubes was observed. X-ray diffraction measurements revealed that oxygen or water molecules in air gradually react with CsSn2Br5 perovskite nanocubes to form Cs2SnBr6 NCs. The stability of Cs2SnBr6 NCs was monitored by time-dependent absorption measurements. Both oxygen and water molecules react with the Cs2SnBr6 NCs to degrade, however water molecules appears largely to react with the NCs. The stability has been improved by dispersing the Cs2SnBr6 NCs in degassed anhydrous solvent.