Photophysical Properties of Submicrometer Ultrathin Perovskite Single-Crystal Films.

Organic-inorganic hybrid perovskite (OIHP) has attracted a great deal of interest with respect to diverse optoelectronic devices. However, the photophysical properties of the OIHP require further understanding because most of the investigations have been conducted with polycrystalline perovskites, which contain high-density structural defects. Here, diverse photophysical properties, including structural characterization, spectroscopic features, and photoexcited products, are studied in submicrometer CHNHPbBr ultrathin single-crystal (UTSC) films. Unlike polycrystalline films and large single crystals, the UTSC film provides a unique platform for studying spectroscopic characteristics of single-crystal perovskites. Compared with the polycrystalline film, the UTSC film presents an atomically flat morphology and near-perfect lattice with a lower defect density, leading to an isotropic system that can be applied in the construction of high-performance optoelectronic devices. Furthermore, a long lifetime emissive channel assigned to the trion is indicated, which is scarcely found in perovskite polycrystalline films. Our results profoundly improve our understanding of their photophysical properties and expand the horizons for perovskite materials in photonic applications.