Optical properties of emeraldine salt polymers from ab initio calculations: comparison with recent experimental data

TL;DR

This study uses ab initio calculations to analyze the optical properties of emeraldine salt polymers, comparing theoretical results with recent experimental data to validate the computational approach.

Contribution

It provides a detailed ab initio analysis of emeraldine salt polymers' optical properties, incorporating intra-band transitions and comparing results with experimental measurements.

Findings

Calculated optical spectra agree well with experimental data

The band structure explains the optical transition features

Intra-band contributions are effectively modeled with a Drude-like term

Abstract

We present absorption coefficient {\alpha}({\omega}), transverse dielectric function {\epsilon}({\omega}), optical conductivity {\sigma}({\omega}), and reflectance R({\omega}) calculated for an emeraldine salt conducting polymer in its crystalline three-dimensional polaronic structure. We utilize Kohn-Sham DFT electronic wavefunctions and energies implemented in the expression of the macroscopic transverse dielectric function in the framework of the band theory without the electron-hole interaction. Contributions of intra-band transitions are taken into account by adding a Drude-like term to the dielectric function calculated ab-initio. Comparison with optical properties, recently measured on high-quality emeraldine salts (Nature 441(2006)65-68), and with optical absorption spectra, recorded on other emeraldine salts, is very satisfactory. The calculated spectra are discussed in terms of energy-band structure, density of states, inter- and intra-band transitions and transverse dielectric function.