a substantial effect on the band structure and electron behavior. Unfortunately, over past few years, most perovskite optoelectronic devices focus on polycrystalline perovskite thin-films, [10][11][12][13] and can only get the average surface-related optoelectronic properties of polycrystalline particles. The random arrangement of surface orientation in polycrystalline perovskite thin films seriously affects the carrier transportability and limits the microscopic photovoltaic performance. [14][15][16] Instead, a single-crystal-basedperovskite device can not only effectively improve photovoltaic performances due to their lower trap-state density and ultralong carrier diffusion lengths, [17][18][19] but also provide great opportunity for tailing the surface-determined optical and electronic properties. [17][18][19][20][21] However, it is still a great challenge to engineer the anisotropic surface of halide perovskite single crystals due to their ionic nature and fast crystallization during their regular solution-based growth, [22][23][24] and it is extremely difficult to quantify the surface-dependent optoelectronic properties as well as the underlying anisotropy mechanism.Herein, we report a one-step atmospheric-pressure chemical vapor deposition (APCVD) method for fabricating uniform perovskite CsPbBr 3 cube and tetrahedron single-crystals with precise control of ( 100) and ( 111) surface anisotropy, respectively (Figure S1, Supporting Information, see Methods in the Supporting Information for more synthesis details). The single-crystal-based optoelectronic devices demonstrated that the preferred (100) surface engineering of CsPbBr 3 singlecrystals enables a lowest surface bandgap energy of 2.33 eV, long carrier lifetime of 8.68 ns and high-rate carrier mobility up to 241 µm 2 V -1 s -1 , whereas the polar (111) surface induces ≈0.16 eV upward surface band bending and ultrahigh charged surface defect density of 1.49 × 10 15 cm -3 . Our results pave an ideal way to optimize the performance of halide-perovskitebased optoelectronic and/or catalysis devices by anisotropic surface engineering. Results and DiscussionScanning electron microscopy (SEM) images (Figure 1A-D) and optical microscopy images (Figures S2 and S3, Supporting Information) show that CsPbBr 3 cubes and tetrahedrons are uniform in size (≈4 µm) and monodispersed on the surface of the SiO 2 /Si substrate. The elemental distribution of Cs, Pb and Br was characterized using scanningelectron microscopy-energydispersive X-ray spectroscopy (SEM-EDS) elemental mapping, Engineering surface structure can precisely and effectively tune the optoelectronic properties of halide perovskites, but are incredibly challenging. Herein, the design and fabrication of uniform all-inorganic CsPbBr 3 cubic/tetrahedral single-crystals are reported with precise control of the ( 100) and ( 111) surface anisotropy, respectively. By combining with theoretical calculations, it is demonstrated that the preferred (100) surface engineering of the CsPbBr 3 single-crystals enables a lo...

Low-dimensional semiconductors can be used for fabrication of various optoelectronic devices due to their fascinating structures and physical properties. Herein, one-dimensional single-crystal antimony sulfide (Sb2S3) rods with tunable lengths/diameters were...

Formamidinium lead triiodide (FAPbI3) perovskite has received great attention because of its distinct optoelectronic property, smaller band gap (~1.5 eV), and higher thermal stability than methylammonium lead triiodide (MAPbI3). However, the efficient synthesis of such perovskite materials on a large scale at a low cost remains a challenge. In this work, mixed-cation FA1−xCsxPbI3 thin films were directly prepared in an atmospheric environment with a high film formation rate, low material loss, low cost, and low requirements for experimental instruments and environment. The as-obtained FAPbI3 films exhibited excellent optoelectronic properties, showing promising applications in the photodetection field.