Carrier Localization and Spontaneous Formation of Two-Dimensional Polarization Domain in Halide Perovskites

TL;DR

This study investigates how polarization domains and carrier localization in halide perovskites like CsPbBr3 influence their long electron-hole recombination times, revealing temperature-dependent structural and electronic behaviors that impact optoelectronic performance.

Contribution

It provides a detailed ab initio analysis of carrier localization and polarization domain formation in halide perovskites, linking these phenomena to long recombination lifetimes and temperature effects.

Findings

Polar grain boundaries form at low temperatures, creating 2D polarization patterns.

Electron and hole localization is influenced by polarization domains and phonon interactions.

Transport at low temperatures is dominated by phonon-assisted variable-range hopping.

Abstract

Halide perovskites are known for their rich phase diagram and superior performance in diverse optoelectronics applications. The latter property is often attributed to the long electron-hole recombination time, whose underlying physical mechanism has been a long-standing controversy. In this Letter, we investigate the transport and localization properties of electron and hole carriers in a prototypical halide perovskite (CsPbBr$_3$), through \textit{ab initio} tight-binding nonadiabatic dynamics approach for large-scale (tens of nm size) supercell calculations, to simulate electron and ion dynamics on the same footing. We found distinct structural, lattice polarization, and electron-phonon coupling properties at low (below 100 K) and high temperatures, consistent with experimental observations. In particular, at low temperature we find spontaneous formation of polar grain boundaries in the nonpolar bulk systems, which result in two-dimensional polarization patterns that serve to localize and separate electrons and holes. We reveal phonon-assisted variable-range hopping mostly responsible for low-temperature transport, and their characteristic frequency correlates with temperature-dependent phonon power spectrum and energy oscillation frequency in nonadiabatic dynamics. We answer the critical questions of long electron-hole recombination lifetime at low temperature and offer the correlation among polarization domains, electron-phonon couplings, and photocarrier dynamics.