Intrinsic Limits of Charge Carrier Mobilities in Layered Halide Perovskites

TL;DR

This study uses advanced ab initio methods to analyze why layered halide perovskites have lower charge carrier mobilities than their three-dimensional counterparts, revealing that increased density of states due to reduced dimensionality is a key factor.

Contribution

The paper provides a detailed ab initio analysis of electron-phonon interactions in layered halide perovskites, identifying intrinsic factors limiting charge mobility.

Findings

Lower mobilities are mainly due to increased electronic density of states near band edges.

Electron-phonon coupling strength is similar across layered and 3D perovskites.

Dimensionality reduction and octahedra connectivity break cause the density of states increase.

Abstract

Layered halide perovskites have emerged as potential alternatives to three-dimensional halide perovskites due to their improved stability and larger material phase space, allowing fine-tuning of structural, electronic, and optical properties. However, their charge carrier mobilities are significantly smaller than that of three-dimensional halide perovskites, which has a considerable impact on their application in optoelectronic devices. Here, we employ state-of-the-art ab initio approaches to unveil the electron-phonon mechanisms responsible for the diminished transport properties of layered halide perovskites. Starting from a prototypical ABX$_{3}$ halide perovskite, we model the case of $n=1$ and $n=2$ layered structures and compare their electronic and transport properties to the three-dimensional reference. The electronic and phononic properties are investigated within density functional theory (DFT) and density functional perturbation theory (DFPT), while transport properties are obtained via the ab initio Boltzmann transport equation. The vibrational modes contributing to charge carrier scattering are investigated and associated with polar-phonon scattering mechanisms arising from the long-range Fr\"ohlich coupling and deformation potential scattering processes. Our investigation reveals that the lower mobilities in layered systems primarily originates from the increased electronic density of states at the vicinity of the band edges, while the electron-phonon coupling strength remains similar. Such increase is caused by the dimensionality reduction and the break in octahedra connectivity along the stacking direction. Our findings provide a fundamental understanding of the electron-phonon coupling mechanisms in layered perovskites and highlight the intrinsic limitations of the charge carrier transport in these materials.