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

Abstract Lead‐free CsSnX 3 perovskite NCs are becoming a promising alternative to CsPbX 3 (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 CsSnX 3 NCs. A method is proposed for synthesizing CsSnX 3 NCs using Cs 2 CO 3 , SnC 2 O 4 , and NH 4 X as corresponding constituent precursors, wherein the ratio of reactants can be easily adjusted. Stable CsSnX 3 NCs can be obtained with the use of antioxidative SnC 2 O 4 as the Sn II precursor. Experimental results show that the improvement of NCs stability is mainly ascribed to the role of oxalate in the SnC 2 O 4 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.