On the interplay of electronic and lattice screening on exciton binding in two-dimensional lead halide perovskites

TL;DR

This study uses advanced simulations to analyze how dielectric effects and electron-phonon interactions influence exciton binding energies in layered lead halide perovskites, aligning well with experimental data.

Contribution

It provides a comprehensive analysis of dielectric confinement and polaron effects on excitons, introducing a variational theory to explain their non-monotonic relationship with layer thickness.

Findings

Dielectric mismatch increases exciton binding energy significantly.

Polaron formation reduces the effect of dielectric confinement.

Exciton binding energies depend non-monotonically on layer thickness.

Abstract

We use path integral Monte Carlo to study the energetics of excitons in layered, hybrid organic-inorganic perovskites in order to elucidate the relative contributions of dielectric confinement and electron-phonon coupling. While the dielectric mismatch between polar perovskite layers and non-polar ligand layers significantly increases the exciton binding energy relative to their three dimensional bulk crystal counterparts, formation of exciton polarons attenuates this effect. The contribution from polaron formation is found to be a non-monotonic function of the lead halide layer thickness, which is clarified by a general variational theory. Accounting for both of these effects provides a description of exciton binding energies in good agreement with experimental measurements. By studying isolated layers and stacked layered crystals of various thicknesses, with ligands of varying polarity, we provide a systematic understanding of the excitonic behavior of this class of materials and how to engineer their photophysics.