Investigation of all-solid-state electrochromic devices with durability enhanced tungsten-doped nickel oxide as a counter electrode

Abstract

Films of tungsten-doped nickel oxide, denoted Ni1-xWx oxide as counter electrode in electrochromic devices were deposited onto indium tin oxide coated glass substrates by reactive dc magnetron sputtering using tungsten-doped nickel alloy target. Electrochromic properties of NixW1-x oxides were evaluated in lithium perchlorate in propylene carbonate. Enhanced cycle stability with moderate optical modulation was obtained for Ni1-xWx oxide film with x = 0.024. Significant degradation in pure NiO film during extended electrochemical cycling caused by microstructural deep trap sites was minimized by W doping. The EC device fabricated with WO3 thin film and Ni1-xWx oxide thin film with x = 0.024 showed stable optical modulation of about 2% reduction from 100 to 1000 cycles. Flexible EC device was also fabricated with WO3 thin film and Ni1-xWx oxide thin film with x = 0.024 deposited on c-ITO/graphene/PET electrode and showed stable cycling performance with maintaining optical modulation of ΔT ≈ 40%.