Chemical vapor deposition growth of single-crystalline cesium lead halide microplatelets and heterostructures for optoelectronic applications

Organic–inorganic hybrid halide perovskites, such as CH3NH3PbI3, have emerged as an exciting class of materials for solar photovoltaic applications; however, they are currently plagued by insufficient environmental stability. To solve this issue, all-inorganic halide perovskites have been developed and shown to exhibit significantly improved stability. Here, we report a single-step chemical vapor deposition growth of cesium lead halide (CsPbX3) microcrystals. Optical microscopy studies show that the resulting perovskite crystals predominantly adopt a square-platelet morphology. Powder X-ray diffraction (PXRD) studies of the resulting crystals demonstrate a highly crystalline nature, with CsPbCl3, CsPbBr3, and CsPbI3 showing tetragonal, monoclinic, and orthorhombic phases, respectively. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies show that the resulting platelets exhibit well-faceted structures with lateral dimensions of the order of 10–50 μm, thickness around 1 μm, and ultra-smooth surface, suggesting the absence of obvious grain boundaries and the single-crystalline nature of the individual microplatelets. Photoluminescence (PL) images and spectroscopic studies show a uniform and intense emission consistent with the expected band edge transition. Additionally, PL images show brighter emission around the edge of the platelets, demonstrating a wave-guiding effect in high-quality crystals. With a well-defined geometry and ultra-smooth surface, the square platelet structure can function as a whispering gallery mode cavity with a quality factor up to 2,863 to support laser emission at room temperature. Finally, we demonstrate that such microplatelets can be readily grown on a variety of substrates, including silicon, graphene, and other two-dimensional materials such as molybdenum disulfide, which can readily allow the construction of heterostructure optoelectronic devices, including a graphene/perovskite/graphene vertically-stacked photodetector with photoresponsivity > 105 A/W. The extraordinary optical properties of CsPbX3 platelets, combined with their ability to be grown on diverse materials to form functional heterostructures, can lead to exciting opportunities for broad optoelectronic applications.