Single-crystal microplates of two-dimensional organic-inorganic lead halide layered perovskites for optoelectronics

Organic-inorganic hybrid perovskites attract considerable attention owing to their applications in high-efficiency solar cells and light emission. Compared with three-dimensional perovskites, two-dimensional (2D) layered hybrid perovskites have a higher exciton binding energy and potentially higher lightemission efficiency. The growth of high-quality crystalline 2D perovskites with a well-defined nanoscale morphology is desirable because they can be suitable building blocks for integrated optoelectronics and (nano) photonics. Herein, we report the facile solution growth of single-crystal microplates of 2D perovskites based on a 2-phenylethylammonium (C6H5CH2CH2NH3+, PEA) cation, (PEA)(2)PbX4 (X = Br, I), with a well-defined rectangular geometry and nanoscale thickness through a dissolution-recrystallization process. The crystal structures of (PEA)(2)PbX4 are first confirmed using single-crystal X-ray diffraction. A solution-phase transport-growth process is developed to grow microplates with a typical size of tens of micrometers and thickness of hundreds of nanometers on another clean substrate different from the substrate coated with lead-acetate precursor film. Surface-topography analysis suggests that the formation of the 2D microplates is likely driven by the wedding-cake growth mechanism. Through halide alloying, the photoluminescence emission of (PEA)(2)Pb(Br, I)(4) perovskites with a narrow peak bandwidth is readily tuned from violet (similar to 410 nm) to green (similar to 530 nm).