Gas-Phase Anion Exchange for Multisegment Heterostructured CsPb(Br1−xClx)3 Perovskite Nanowires

Abstract

Metal-halide perovskites (MHPs) are promising as active optoelectronic materials for a diverse range of devices. Anion exchange is a post-growth modification of MHP materials that allows tuning of the band gap and crystal structure by exposure to alternative halides, normally using solution methods. Here, low temperature gas-phase anion exchange for the conversion of CsPbBr3 nanowires (NW) into CsPb(Br1−xClx) NWs using two media, fuming HCl and Cl2 gas, is systematically investigated. It is found that both methods can be used to tune the composition in the full range with excellent control. While fuming HCl is the simplest process, Cl2 gives similar results with no surface damage and better process control. Based on a simple solid diffusion model, an average diffusivity of 1.4 × 10−12 cm2s−1 is extracted for Cl-anions inside CsPbBr3. By combining the Cl2 exchange process with electron-beam lithography patterning, heterojunction NWs with varying halide compositions are produced, including complex barcode-like NWs with segment lengths as short as 500 nm. Designed heterostructures provide an important basis for optoelectronic device applications of MHPs, and gas-phase anion exchange should be suitable for any MHP morphology.