Limits to Electrical Mobility in Lead-Halide Perovskite Semiconductors

TL;DR

This study reveals that polycrystalline lead-halide perovskite films have electrical mobilities approaching single crystals at room temperature, with charge scattering primarily due to phonons and grain boundaries, promising for various electronic devices.

Contribution

The paper provides a comprehensive understanding of charge scattering mechanisms in lead-halide perovskites, bridging the performance gap between polycrystalline films and single crystals.

Findings

Frohlich scattering dominates charge mobility limitation.

Grain boundaries further reduce mobility in polycrystalline films.

Photon reabsorption explains diffusion length discrepancies.

Abstract

Semiconducting polycrystalline thin films are cheap to produce and can be deposited on flexible substrates, yet high-performance electronic devices usually utilize single-crystal semiconductors, owing to their superior electrical mobilities and longer diffusion lengths. Here we show that the electrical performance of polycrystalline films of metal-halide perovskites (MHPs) approaches that of single crystals at room temperature. Combining temperature-dependent terahertz conductivity measurements and ab initio calculations we uncover a complete picture of the origins of charge scattering in single crystals and polycrystalline films of CH$_3$NH$_3$PbI$_3$. We show that Fr\"ohlich scattering of charge carriers with multiple phonon modes is the dominant mechanism limiting mobility, with grain-boundary scattering further reducing mobility in polycrystalline films. We reconcile the large discrepancy in charge diffusion lengths between single crystals and films by considering photon reabsorption. Thus, polycrystalline films of MHPs offer great promise for devices beyond solar cells, including transistors and modulators.