“…Depending on the rapid progress of metallic halide perovskites with ABX 3 chemical constitution in the past decade, solution-grown perovskite single crystals (PSCs) without grain boundary provide an ideal material prototype for studying the intrinsic physicochemical properties and possess superior crystalline stability in comparison with polycrystal and nanocrystal forms. − From the perspective of lattice stability, only Goldschmidt’s tolerance factor τ resting with the ionic radius of perovskite components located between 0.9 and 1.0 is generally viewed as a good fit for perovskites, indicating the likelihood of highly symmetric cubic structures at normal pressure and temperature. − Regarding the most attractive iodide PSCs, like MAPbI 3 , the stable structure is found to be tetragonal phase between 165 and 327 K. − Owing to the intrinsic otherness of the tetragonal crystal structure along different directions, the optoelectronic properties of MAPbI 3 single crystals is anisotropic as well. − Conventionally, solution-grown MAPbI 3 single crystals in γ-butyrolactone (GBL) solvent usually expose (100), (010), and (112) facets in a rhombic dodecahedron shape, yet the theoretical calculation and experimental verification reveal the [001] crystalline direction indeed possesses a superior absorption coefficient, carrier dynamic, and the like . Therefore, regulation of the crystal orientation of PSCs plays a role of critical significance toward optoelectronic device applications.…”