Antioxidative Stannous Oxalate Derived Lead-Free Stable CsSnX3 (X=Cl, Br, and I) Perovskite Nanocrystals

Lead-free CsSnX3 perovskite NCs are becoming a promising alternative to CsPbX3 (X=Cl, Br, I), but suffer from extremely poor stability. Herein, we highlight the significant effect of Sn-II precursors used in the synthesis on the stability of the resultant CsSnX3 NCs. A method is proposed for synthesizing CsSnX3 NCs using Cs2CO3, SnC2O4, and NH4X as corresponding constituent precursors, wherein the ratio of reactants can be easily adjusted. Stable CsSnX3 NCs can be obtained with the use of antioxidative SnC2O4 as the Sn-II precursor. Experimental results show that the improvement of NCs stability is mainly ascribed to the role of oxalate in the SnC2O4 precursor. Oxalate ion has a strong antioxidative ability and can effectively inhibit the oxidation of Sn-II during the synthesis. Besides, oxalate as a bidentate capping ligand is shown to be coordinated on the surface of formed NCs. This can not only passivate the uncoordinated Sn on the surface but also prevent the oxidation of the NCs.

Automated summary

The use of antioxidative SnC2O4 as the Sn-II precursor in synthesizing CsSnX3 perovskite NCs significantly improves their stability, mainly attributed to the antioxidative ability of the oxalate ion. Oxalate acts as a bidentate capping ligand on the surface of formed NCs, passivating uncoordinated Sn and preventing oxidation of the NCs.