Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic-Inorganic Lead Halide Perovskites

TL;DR

This study combines theoretical and experimental approaches to analyze X-ray absorption spectra of hybrid lead halide perovskites, revealing exciton-dominated features primarily influenced by inorganic components.

Contribution

It provides new insights into the core-level excitations of hybrid perovskites, emphasizing the inorganic framework's role over organic groups in spectral fingerprints.

Findings

Absorption spectra are dominated by bound excitons with significant binding energies.

Spectra of $ extrm{MAPbI}_3$ and $ extrm{PbI}_2$ are remarkably similar.

Organic groups have negligible influence on core excitation fingerprints.

Abstract

In a combined theoretical and experimental work, we investigate X-ray Absorption Near-Edge Structure (XANES) spectroscopy of the I $L_3$ and the Pb $M_5$ edges of the methylammonium lead iodide ($\textrm{MAPbI}_3$) hybrid inorganic-organic perovskite and its binary phase $\textrm{PbI}_2$. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred meV and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in $\textrm{MAPbI}_3$ are essentially given by its inorganic component, with negligible influence from the organic groups. The theoretical analysis complementing experimental observations provides the conceptual insights required for a full characterization of this complex material.