Halide diffusion in mixed-halide perovskites and heterojunctions

TL;DR

This study uses neural network-enhanced molecular dynamics to analyze halide defect diffusion in mixed-halide perovskites, revealing how interfaces influence ion migration and phase behavior.

Contribution

It provides new insights into halide defect diffusion mechanisms in mixed-halide perovskites and the role of heterojunction interfaces, using advanced simulation techniques.

Findings

Enhanced diffusion of vacancies and interstitials in mixed halide compounds.

Differences in mobility between Br and I ions in mixed compounds.

Interface structure affects halide migration across heterojunctions.

Abstract

Migration of halide defects guides ion transport in metal halide perovskites and controls the kinetics of halide mixing and phase separation. We study the diffusion of halide vacancies and interstitials in \ce{CsPb(I_{x}Br_{1-x})_{3}} and \ce{CsPbI_{3}}/\ce{CsPbBr_{3}} heterojunctions by molecular dynamics simulations using neural network potentials trained on density functional theory calculations. We observe enhanced diffusion of both vacancies and interstitials in the mixed halide compounds compared to the single halide ones, as well as a difference in mobility between Br and I ions in the mixed compound. Diffusion across heterojunctions is governed by the interface structure, where a Br-rich interface blocks migration of vacancies in particular, but an I-rich interface is permeable.