Role of lithium intercalation in fluorine-doped tin oxide thin films: Ab-initio calculations and experiment

TL;DR

This study combines experimental techniques and DFT calculations to explore how lithium intercalation affects the electronic, electrochemical, and electrochromic properties of fluorine-doped tin oxide thin films, revealing lithium's incorporation into the lattice.

Contribution

It provides new insights into lithium's role in modifying FTO properties through combined experimental and computational analysis.

Findings

FTO exhibits electrochromism with high coloration efficiency

DFT shows lithium remains ionized, raising the Fermi level

XPS indicates lithium incorporation into SnO₂ lattice

Abstract

Using a combination of experimental techniques and density functional theory (DFT) calculations, the influence of lithium insertion on the electronic and electrochemical properties of fluourine-doped SnO$_2$ (FTO) is assessed. For this purpose, we investigate the electrochromic behavior of commercial FTO electrode embedded in a solution of lithium perclorate (LiClO$_4$). The electrochromic properties are evaluated by UV-VIS spectroscopy, cyclic voltammetry, and chronoamperometry. These tests show that FTO exhibits electrochromism with a respectable coloration efficiency ($\eta=47.9$ cm$^2$/C @ 637 nm). DFT study indicates that lithium remains ionized in the lattice, raising the Fermi level about 0.7 eV deep into the conduction band. X-ray photoelectron spectroscopy (XPS) is used to study chemical bonding and oxidation states. XPS analysis of the Sn 3d core levels reveals that lithium insertion in FTO induces a shift of 350 meV in the Sn 3d states suggesting that lithium is incorporated into the SnO$_2$ lattice.