Peak Broadening in Photoelectron Spectroscopy of Amorphous Polymers: the Leading Role of the Electrostatic Landscape

TL;DR

This study introduces a computational protocol to quantify how local electrostatic inhomogeneities in amorphous polymers cause significant peak broadening in photoelectron spectra, highlighting the impact of polar groups on spectral features.

Contribution

The paper presents the first computational approach to assess solid-state electrostatic effects on photoelectron peak broadening in amorphous polymers.

Findings

Electrostatic inhomogeneities cause 0.2-0.7 eV Gaussian broadening.

Broader broadening observed in acrylate-based polymers.

Polar groups influence the electrostatic landscape and spectral broadening.

Abstract

The broadening in photoelectron spectra of polymers can be attributed to several factors, such as light source spread, spectrometer resolution, finite lifetime of the hole state, and solid-state effects. Here, for the first time, we set up a computational protocol to assess the peak broadening induced for both core and valence levels by solid-state effects in four amorphous polymers by using a combination of density functional theory, many-body perturbation theory, and classical polarizable embedding. We show that intrinsic local inhomogeneities in the electrostatic environment induce a Gaussian broadening of $0.2$-$0.7$~eV in the binding energies of both core and semi-valence electrons, corresponding to a full width at half maximum (FWHM) of $0.5$-$1.7$~eV for the investigated systems. The induced broadening is larger in acrylate- than in styrene- based polymers, revealing the crucial role of polar groups in controlling the roughness of the electrostatic landscape in the solid matrix.