Design Growth of Triangular Pyramid MAPbBr₃ Single Crystal and Its Photoelectric Anisotropy between (100) and (111) Facets

Abstract

CH3NH3PbBr3 (MAPbBr3), one of the classical members in the organic–inorganic hybrid perovskite family that presents excellent advantages in high photon absorption efficiency and long carrier transport distance, is expected to break the record in responsiveness and efficiency as a photodetector, because single crystal is superior to its thin films, nanowires, and other counterparts. Moreover, single crystal provides adequate media to reveal the intrinsic photoelectric properties, such as defect-related dark current, mixed-ionic conductivities, etc. The mixed-ionic conductivities in MAPbBr3 single crystal are considered to be associated with the atomic packing densities, which are deemed as crystalline oriented or anisotropic. In this study, a series of large-sized MAPbBr3 single crystals with (100) and (111) facets exposed were successfully grown through a crystal-limiting method. By fabricating metal–semiconductor–metal planner photodetectors on both (100) and (111) facets with Au interdigital electrodes in only a MAPbBr3 single crystal, the photoelectric anisotropy was systematically compared in terms of ion migration and the anisotropy of current and on–off ratios. This reveals that the higher MA+ and [PbBr6]4– densities in (111) plane cause a higher built-in electric field, which ultimately affects the dark current, photocurrents, and on–off ratios.