Influence of Lithium Interstitial Doping on the Optoelectronic Properties of NiO and WO$_3$

TL;DR

This study uses first principles calculations to explore how lithium interstitial doping affects the structural, electronic, and optical properties of NiO and WO$_3$, revealing increased metallicity and absorption changes relevant for electrochromic applications.

Contribution

It provides new insights into the effects of Li interstitial doping on NiO and WO$_3$, highlighting the transition to metallic-like behavior and optical property modifications.

Findings

Li doping induces metallic-like behavior in NiO and WO$_3$ at low concentrations.

Li-doped NiO shows increased visible light absorption.

Li-doped WO$_3$ exhibits enhanced absorption across the spectrum, especially in the infrared.

Abstract

First principles calculations through density functional theory (DFT)+$U$ method were performed to assess the effect of Li interstitial doping on the optoelectronic properties of NiO and of cubic, hexagonal, and monoclinic WO$_3$. The implications on the structural and electronic properties and their relationship with the optical properties, such as dielectric response and absorption coefficient in the context of electrochromism, are discussed. Li interstitial doping (i.e., electron doping) turns these materials metallic-like even for low Li concentration ($x<0.083$). In metallic-like materials, optical properties are largely influenced by intraband transitions. Compared to NiO, Li-doped NiO shows larger absorption in the visible region while, with respect to WO$_3$, Li-doped WO$_3$ exhibits an increment in absorption in the whole spectrum, particularly, in the infrared region. These results help to understand the changes in optical properties observed in electrochromic devices based on these materials.