Precise Facet Engineering of Perovskite Single Crystals by Ligand-Mediated Strategy

Inorganic–organic hybrid perovskite single crystals are potential materials for the application of high performance optoelectronic devices. The exposed surface of single crystals can dramatically affect the measured properties. Facet-dependent behaviors are also speculated. However, impeded by the lack of facile facet engineering strategy for inorganic–organic hybrid perovskites, the relationship between different facets and respective performance remains elusive. In this work, we present a simple approach of ligand-mediated crystal growth to control the shape and the exposed facets of methylammonium lead iodide single crystals. The addition of oleylamine ligand can trigger the continuous morphological transition from dodecahedral-shaped single crystal enclosed by (100)T and (112)T to cubic-shaped single crystal enclosed by (110)T and (002)T while maintaining the material composition and crystalline phase. We fabricated single crystal based photodetectors and carried out the first unambiguous study on the relationship between facet structure and device performance. This report opens a new paradigm to reveal the facet-dependent properties and to enhance the device performance of single crystal.