Confined-solution process for high-quality CH₃NH₃PbBr₃ single crystals with controllable morphologies

Solution processes have shown excellent potential for application to the growth of single-crystal materials. We have developed a confined-solution method for the preparation of single crystals with a controlled morphology. By confining the precursor solution within a micrometer-thick cavity and then controlling the saturation by adjusting the temperature gradient and fluid flow, high-quality CH₃NH₃PbBr₃ single crystals with tunable morphologies could be obtained. The morphologies of the CH₃NH₃PbBr₃ can be adjusted from sub-square centimeter-scale thin sheets that are square or rectangular, to one-dimensional wires with lengths in the order of centimeters, simply by changing the temperature. The thicknesses of the CH₃NH₃PbBr₃ sheets could be adjusted from hundreds of nanometers to tens of microns. The CH₃NH₃PbBr₃ sheets feature very clean surfaces with an atomic-scale roughness. This simple strategy provides a means of growing high-quality single crystals with clean surfaces, which realize high levels of performance when applied to devices.