Theoretical study of perovskite nanowires optical response to hydrogen halides vapor exposure

Highly sensitive detection of harmful to the human health and environment hydrogen halide vapors is one of the key problems for the chemical industry. The available electrochemical and optical sensors most often show no selectivity to different hydrogen halides and can be produced via costly high-tech fabrication. In contrast to them, CsPbBr3 perovskite nanowires (NWs) exhibiting laser generation are capable of selective and precise detecting for HCl and HI. Exposure of a single NW to these analytes results in an anion exchange that modifies the chemical composition of the NW and therefore invokes a small spectral shift of the laser peak. Herein we propose a theoretical model describing such an optical response. Taking into account that the anion exchange occurs at the surface of the NW and initiates the formation of a core-shell structure, we perform numerical estimation of the eigenmode spectral position for different thicknesses of the chlorine-and iodine-rich shell. Calculations reveal that even a 10 nm shell causes a noticeable spectral shift of 0.81 and 0.63 nm for eigenmode in CsPbBr3-CsPbCl3 and CsPbBr3-CsPbl3 core-shell NWs, respectively.