Kinetically Controlled Growth of Sub‐Millimeter 2D Cs₂SnI₆ Nanosheets at the Liquid–Liquid Interface

Abstract

Cs2SnI6 perovskite displays excellent air stability and a high absorption coefficient, promising for photovoltaic and optoelectronic applications. However, Cs2SnI6‐based device performance is still low as a result of lacking optimized synthesis approaches to obtain high quality Cs2SnI6 crystals. Here, a new simple method to synthesize single crystalline Cs2SnI6 perovskite at a liquid–liquid interface is reported. By controlling solvent conditions and Cs2SnI6 supersaturation at the liquid–liquid interface, Cs2SnI6 crystals can be obtained from 3D to 2D growth with controlled geometries such as octahedron, pyramid, hexagon, and triangular nanosheets. The formation mechanisms and kinetics of complex shapes/geometries of high quality Cs2SnI6 crystals are investigated. Freestanding single crystalline 2D nanosheets can be fabricated as thin as 25 nm, and the lateral size can be controlled up to sub‐millimeter regime. Electronic property of the high quality Cs2SnI6 2D nanosheets is also characterized, featuring a n‐type conduction with a high carrier mobility of 35 cm2 V−1 s−1. The interfacial reaction‐controlled synthesis of high‐quality crystals and mechanistic understanding of the crystal growth allow to realize rational design of materials, and the manipulation of crystal growth can be beneficial to achieve desired properties for potential functional applications.

Metal Ion-Incorporated Lead-Free Perovskites toward Broadband Photodetectors

“…To synthesize high-quality crystals, we first reported a solution-based method to grow single-crystalline Cs 2 SnI 6 at the liquid−liquid interface by dissolving two reagents (CsI and SnI 4 ) into two immiscible solvents. 48 Due to the immiscible nature of the two solvents, the precipitation of Cs 2 SnI 6 is constrained at the interface. By controlling solvent conditions and Cs 2 SnI 6 supersaturation at the liquid−liquid interface, Cs 2 SnI 6 crystals can be obtained with controlled geometries such as triangle, hexagon, truncated tetrahedron, and octahedron (see Methods; Figure S1, Supporting Information).…”

“…To synthesize high-quality crystals, we first reported a solution-based method to grow single-crystalline Cs 2 SnI 6 at the liquid–liquid interface by dissolving two reagents (CsI and SnI 4 ) into two immiscible solvents . Due to the immiscible nature of the two solvents, the precipitation of Cs 2 SnI 6 is constrained at the interface.…”

Stability of Low-index Surfaces of Cs2SnI6 Studied by First-principles Calculations

“…It can be seen that the stoichiometric CsI3-terminated (111) surface consistently has the lowest surface energy, indicating that it is the most thermodynamically favored surface among the seven terminations, in agreement with the recent experimental reports. [25][26] 3 Conclusion…”

“…Xu et al [24] reported a general approach to synthesize layered nanoplatelets of Cs2SnI6. Zhu et al [25] revealed that Cs2SnI6 crystals have a preferential growth of (111) surface. Several experiments also found that Cs2SnI6 tends to grow along the <111> direction [26][27][28] .…”

Deciphering the Role of Water in Promoting the Optoelectronic Performance of Surface-Engineered Lead Halide Perovskite Nanocrystals

“…Interestingly, a tiny drop of water, 0.2% (v/v), instantly changed the emission color from blue-green to a highly emissive green, which is in line with what we will discuss later. It is anticipated that the interaction of perovskite NCs with an extremely small amount of water leads to chemical dissolution, 43 formally releasing the constituent ions of FAPbBr 3 (FA + , Br − , Pb 2+ ) from the surface. Notably, the dissolution seems to take place at preferential sites instead of exhibiting a uniform dissolution of the crystal (Figures S8 and S9).…”