Composition-Graded Cesium Lead Halide Perovskite Nanowires with Tunable Dual-Color Lasing Performance.

Cesium lead halide (CsPbX3 ) perovskite has emerged as a promising low-threshold multicolor laser material; however, realizing wavelength-tunable lasing output from a single CsPbX3 nanostructure is still constrained by integrating different composition. Here, the direct synthesis of composition-graded CsPbBrx I3-x nanowires (NWs) is reported through vapor-phase epitaxial growth on mica. The graded composition along the NW, with an increased Br/I from the center to the ends, comes from desynchronized deposition of cesium lead halides and temperature-controlled anion-exchange reaction. The graded composition results in varied bandgaps along the NW, which induce a blueshifted emission from the center to the ends. As an efficient gain media, the nanowire exerts position-dependent lasing performance, with a different color at the ends and center respectively above the threshold. Meanwhile, dual-color lasing with a wavelength separation of 35 nm is activated simultaneously at a site with an intermediate composition. This position-dependent dual-color lasing from a single nanowire makes these metal halide perovskites promising for applications in nanoscale optical devices.