Structural, optical, and electrical properties of phase-controlled cesium lead iodide nanowires

Cesium lead iodide (CsPbI<sub>3</sub>), in its black perovskite phase, has a suitable bandgap and high quantum efficiency for photovoltaic applications. However, CsPbI<sub>3</sub> tends to crystalize into a yellow non-perovskite phase, which has poor optoelectronic properties, at room temperature. Therefore, controlling the phase transition in CsPbI<sub>3</sub> is critical for practical application of this material. Here we report a systematic study of the phase transition of one-dimensional CsPbI<sub>3</sub> nanowires and their corresponding structural, optical, and electrical properties. We show the formation of perovskite black phase CsPbI<sub>3</sub> nanowires from the non-perovskite yellow phase through rapid thermal quenching. Post-transformed black phase CsPbI<sub>3</sub> nanowires exhibit increased photoluminescence emission intensity with a shrinking of the bandgap from 2.78 to 1.76 eV. The perovskite nanowires were photoconductive and showed a fast photoresponse and excellent stability at room temperature. Finally, these promising optical and electrical properties make the perovskite CsPbI<sub>3</sub> nanowires attractive for a variety of nanoscale optoelectronic devices.