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

Cesium lead iodide (CsPbI), in its black perovskite phase, has a suitable bandgap and high quantum efficiency for photovoltaic applications. However, CsPbI tends to crystalize into a yellow non-perovskite phase, which has poor optoelectronic properties, at room temperature. Therefore, controlling the phase transition in CsPbI is critical for practical application of this material. Here we report a systematic study of the phase transition of one-dimensional CsPbI nanowires and their corresponding structural, optical, and electrical properties. We show the formation of perovskite black phase CsPbI nanowires from the non-perovskite yellow phase through rapid thermal quenching. Post-transformed black phase CsPbI 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. These promising optical and electrical properties make the perovskite CsPbI3 nanowires attractive for a variety of nanoscale optoelectronic devices. [ABSTRACT FROM AUTHOR]