(Invited) Ultrasonic Spray Coating of Electrochromic Nanomaterials

Abstract

Ultrasonic spray deposition is a promising and versatile method for both fundamental and industrial researches and applications. It leads to the formation of uniform thin films on large area substrates at atmospheric pressure, with a fine control of the resulting morphology and thickness by adjustment of the practical spray conditions (substrate temperature, nozzle-to-substrate distance, deposition pattern, solution flow rate, carrier gas nature and pressure…). The ultrasonic atomization of the injected precursor solution/suspension is also particularly advantageous as it reduces overspray and energy consumption [1-2]. In our recent works [3-7], we are considering the spray deposition of thin films of electrochromic oxides such as WO3and NiO, which are exploited as nanomaterials for various optical-related devices, notably “smart windows” for energy-efficient fenestration in glass buildings [8-9]. A specific attention is thus paid to the composition of the sprayed solution/suspension (precursor type and concentration, solvent…) as it has a significant influence on film deposition mechanisms and properties. Substrate nature (morphology, crystallinity, conductivity…) is of particular importance too, and different types of transparent conductive oxide (TCO) coated glass are therefore investigated. Incorporation of selected surfactants is also acknowledged for influencing wettability, nucleation and growth processes, and resulting functionality. Consequent characterizations analyze crystallinity, microstructure and porosity, ionic reversibility and diffusion, cycling response, optical modulation, coloration/bleaching kinetics, tint and haze.