All‐inorganic CsPbI3 quantum dots (QDs) have shown great potential in photovoltaic applications. However, their performance has been limited by defects and phase stability. Herein, an anion/cation synergy strategy to improve the structural stability of CsPbI3 QDs and reduce the pivotal iodine vacancy (VI) defect states is proposed. The Zn‐doped CsPbI3 (Zn:CsPbI3) QDs have been successfully synthesized employing ZnI2 as the dopant to provide Zn2+ and extra I−. Theoretical calculations and experimental results demonstrate that the Zn:CsPbI3 QDs show better thermodynamic stability and higher photoluminescence quantum yield (PLQY) compared to the pristine CsPbI3 QDs. The doping of Zn in CsPbI3 QDs increases the formation energy and Goldschmidt tolerance factor, thereby improving the thermodynamic stability. The additional I− helps to reduce the VI defects during the synthesis of CsPbI3 QDs, resulting in the higher PLQY. More importantly, the synergistic effect of Zn2+ and I− in CsPbI3 QDs can prevent the iodine loss during the fabrication of CsPbI3 QD film, inhibiting the formation of new VI defect states in the construction of solar cells. Consequently, the anion/cation synergy strategy affords the CsPbI3 quantum dot solar cells (QDSC) a power conversion efficiency over 16%, which is among the best efficiencies for perovskite QDSCs.
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 SnII 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 SnII 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 SnII 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.
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.
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