Crystal structure and luminescence of Cs-Pb-Sn-Br nanocrystals

Sn 2+ ions were introduced in Cs-Pb-Br nanocrystals (NCs) to test the change of crystal structure and photoluminescence (PL) property. In the cases of Sn/Pb ratios less than 20%, the CsPb 1- x Sn x Br 3 NCs revealed CsPbBr 3 crystal structure. With increasing the Sn/Pb ratio, Cs-Pb-Sn-Br NCs exhibited a mixture phase of CsPbBr 3 and Cs 4 PbBr 6 . The NCs show bright PLQYs (87%) for Sn/Pb molar ratio of 30%. This is ascribed to little amount Cs 4 PbBr 6 decreased the electrons and holes non-radiation recombination of CsPbBr 3 . With increasing the Sn/Pb ratio to 80%, the Cs 4 Pb 1- x Sn x Br 6 NCs exhibited pure Cs 4 PbBr 6 phase structure. Furthermore, a weak blue-emitting peak around 450 nm was observed for the Cs 4 Pb 1- x Sn x Br 6 NCs. This confirms that Sn 2+ ions were successfully introduced into Cs 4 PbBr 6 structure. The morphologies of samples changed from initial cubic to hexagonal with increasing Sn/Pb ratios from 20 to 80%. The excitons and free carrier dynamics of the NCs were discussed. Graphical abstract