Controllable growth of two-dimensional perovskite microstructures

Two-dimensional (2D) Ruddlesden–Popper perovskites with high exciton binding energy and great environmental stability have recently attracted great attention for their promising potential optoelectronic applications. The controllable growth of 2D perovskites with desired shapes would be critical for improving the performance of 2D perovskite-based optoelectronic devices. However, the investigation on this is still in its infancy. Here, we report on the controllable synthesis of 2D (C4H9NH3)2PbI4 microstructures with a butterfly shape, (C4H9NH3)2(CH3NH3)Pb2I7 and (C4H9NH3)2PbI4/(C4H9NH3)2(CH3NH3)Pb2I7 microstructures with a square shape by a solution-processing method. We have systematically investigated the influence of the substrate, mass ratio and crystallization temperature on the morphology evolution of the as-synthesized 2D perovskite microstructures. Atomic force microscopy (AFM) and optical microscopy (OM) images show that the size and thickness of the resultant products are positively correlated with their mass ratio and negatively correlated with their crystallization temperature. X-ray diffraction (XRD) patterns, fluorescence imaging, temperature-dependent photoluminescence (PL) and absorption studies confirm the crystalline structures and optical properties of the as-synthesized regularly shaped 2D perovskite microstructures. Our studies provide a simple method to controllably synthesize 2D perovskite microstructures without using very toxic solvents and thus offer a platform to investigate the optical and charge transport properties of 2D perovskite materials for the further design of new device architectures with enhanced performance.