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

Abstract

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.

Oxalate Pushes Efficiency of CsPb0.7Sn0.3IBr2 Based All‐Inorganic Perovskite Solar Cells to over 14%

“…This interaction not only slows down film crystallization but also mitigates the oxidation of Sn 2+ . [ 33 ] Figure 2b shows the photographs of the control and ZnOX perovskite precursor solutions at different stages. Both as‐prepared perovskite solutions present a semitransparent light‐yellow color.…”

Advances and Challenges in Tin Halide Perovskite Nanocrystals

“…Recently, Kang et al used antioxidative oxalate ligand to improve the stability of THP NCs . They chose stannous oxalate (SnC 2 O 4 ), Cs 2 CO 3 , and NH 4 I as the precursors of Sn, Cs, and I, respectively, to prepare CsSnI 3 NCs via the hot-injection approach.…”

“…This can be understood by comparing the standard redox potentials of Sn 2+ /Sn 4+ and Pb 2+ /Pb 4+ (+0.15 V and +1.67 V, respectively) The easy oxidation of Sn 2+ to Sn 4+ leads to a much easier degradation of Sn-based perovskite lattices compared with their Pb-based counterparts, which becomes even worse when their sizes are down to the nanometer scale. Some strategies, such as ligand engineering, metal-ion doping or alloying engineering, and core–shell structure construction, may help figure out this issue, some of which were validated in recent studies. − In the past, a number of comprehensive reviews on THP polycrystalline films and their device applications have been reported. ,− However, a concise review regarding THP NCs has not emerged. Considering the great promise of THP NCs for the next-generation Pb-free halide perovskite optoelectronic devices, it is very crucial to provide an up-to-date overview of pioneering advances in this exciting field.…”

Progresses on Novel B‐Site Perovskite Nanocrystals

“…also highlighted the significant effect of Sn II precursor used during the synthesis process. [ 63 ] It is known that oxalic acid is a kind of strong reducing reagent exhibiting antioxidative effects. [ 80 ] Accordingly, SnC 2 O 4 as a stannous precursor can show higher stability than SnX 2 , so Kang and co‐workers chose SnC 2 O 4 as the Sn II precursor instead of SnX 2 in a hot‐injection process.…”

“…have proved the significant impact of Sn 2+ in the synthesis on the stability of the consequent CsSnX 3 PNCs. [ 63 ] PL spectrum of SnC 2 O 4 –CsSnX 3 NCs showed PL peaks centered at 475, 677, and 849 nm for CsSnCl 3 , CsSnBr 3 , and CsSnI 3 NCs, with the corresponding PLQE measuring to be 0.17%, 0.60%, and 0.35%, respectively. PL decay tests demonstrated the PL lifetimes were calculated to be 2.14, 4.75, and 2.62 ns for CsSnCl 3 , CsSnBr 3 , and CsSnI 3 NCs, respectively.…”