Importance of nonlinear long-range electron-phonon interaction on the carrier mobility of anharmonic halide perovskites

TL;DR

This study demonstrates that nonlinear long-range electron-phonon interactions significantly influence the carrier mobility in anharmonic halide perovskites, challenging the common linear interaction assumption and highlighting the need for their inclusion in theoretical models.

Contribution

The paper introduces a first-principles method to account for nonlinear electron-phonon interactions in anharmonic halide perovskites, revealing their substantial impact on electron mobility.

Findings

Nonlinear electron-phonon interactions contribute about 10% to room-temperature mobility.

Including nonlinear interactions alters the temperature dependence of mobility.

Low phonon frequencies in CsPbI3 amplify the importance of nonlinear effects.

Abstract

The interaction between the electrons and the lattice vibrations in a solid is responsible for various important effects, such as formation of polarons, temperature dependent bandgaps, phonon-limited carrier transport, and conventional superconductivity. Most works assume a linear electron-phonon interaction, where the electron only interacts with one phonon at a time. However, the validity of this assumption has not been verified in polar anharmonic materials, where large ionic displacements may invalidate the assumption of linear interaction. Here, we show that nonlinear electron-phonon interactions contribute significantly to the finite-temperature electron mobility of the inorganic lead halide perovskite CsPbI$_3$. We calculate the electron mobility from first principles using the self-energy relaxation time approximation and the long-range approximation. The effect of nonlinear interaction is taken into account using the recently derived expression for the long-range part of the one-electron-two-phonon matrix element. We show that due to the low phonon frequencies of CsPbI$_3$, the one-electron-two-phonon interaction changes the temperature scaling of the mobility and contributes about 10\% to the mobility at room temperature. The results underscore the importance of including nonlinear electron-phonon interaction in anharmonic halide perovskites.