Direct synthesis of cubic phase CsPbI3 nanowires

Abstract

One-dimensional all-inorganic halide perovskites have emerged as one of the most prominent materials in the application of optoelectronic devices due to their remarkable properties such as a low number of defects, morphological anisotropy, mechanical flexibility and fast charge transfer capability. Particularly, cubic (α) phase CsPbI₃ has the narrowest band gap of 1.73 eV among all-inorganic lead halide perovskites, exhibiting the greatest potential in solar cell applications. However, the direct synthesis of room temperature stabilized α-CsPbI₃ nanowires is challenging and remains unfulfilled because the synthesis reaction usually involves a phase change process, resulting in an undesired orthorhombic (δ) phase with a wider bandgap of 2.82 eV. Here, we report a low-temperature approach to directly synthesize highly stabilized α-CsPbI₃ nanowires. Low reaction temperature, capping ligand protection, and extended growth time are employed to successfully grow α-CsPbI₃ nanowires. The as-synthesized α-CsPbI₃ nanowires are 10–20 μm in length and 5–80 nm in diameter. The X-ray diffraction (XRD), photoluminescence (PL), and UV-vis absorption results verify that these cubic phase nanowires maintain excellent stability at room temperature for 90 days. The CsPbI₃ nanowires show a PL peak located at around 685 nm and the UV-vis absorption spectrum further reveals that the band gap is about 1.77 eV. The excellent optical properties of the phase-stable CsPbI₃ nanowires offer great potential in the field of optoelectronic devices.