Cs2SnI6perovskite 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 Cs2SnI6crystals. Here, a new simple method to synthesize single crystalline Cs2SnI6perovskite at a liquid–liquid interface is reported. By controlling solvent conditions and Cs2SnI6supersaturation at the liquid–liquid interface, Cs2SnI6crystals 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 Cs2SnI6crystals 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 Cs2SnI62D nanosheets is also characterized, featuring a n‐type conduction with a high carrier mobility of 35 cm2V−1s−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.
Large‐scale synthesis of van der Waals (vdW) metal–organic framework (MOF) nanosheets with controlled crystallinity and interlayer coupling strength is one of the bottlenecks in 2D materials that has limited its successful transition to large‐scale applications. Here, scalable synthesis of mBDC (m = Zn and Cu) 2D MOFs at large scales through a biphase method is demonstrated. The results show replacing water molecules with pyridine eliminates hydrogen bond formation at metal cluster sites. This prohibits tight coupling across adjacent MOF layers and sustains controllable 2D vdW MOF growth. It is further shown that control over the growth speed, crystallinity, and thickness can be achieved by addition of a controlled amount of triethylamine and formic acid to achieve highly crystalline vdW MOF nanosheets with extraordinarily high aspect ratio. The described synthesis route can easily be scaled up for large‐scale production either by deposition onto desired substrates or in crystalline layered powder form. Owing to its large lateral size, vdW nature, and high crystallinity, it is possible to perform atomic force microscopy, Kelvin probe force microscopy, and Raman measurements on the 2D MOFs. The results not only establish their vibrational properties and layer‐dependent responses but also show striking differences from other 2D inorganic materials.more » « less
- NSF-PAR ID:
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Medium: X
- Sponsoring Org:
- National Science Foundation
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