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.