Infrared analysis of electrochromic nickel oxide coatings

Abstract

Electrochromic nickel oxide based thin film coatings have been prepared on transparent conducting electrodes using anodic electrodeposition and colloidal precipitation techniques. Coatings were deposited from solutions containing nickel sulphate, ammonium hydroxide, and a solution stabilizer, polyoxyethylene sorbitan monolaurate (a nonionic surfactant). The films were cycled between their colored and bleached states using a 3-electrode cell containing 1 M KOH electrolyte. The dependence of the optical and electrochromic properties of the coatings on bath concentration and deposition time was investigated. Films were analyzed using Fourier transform spectrophotometry, UV/VIS/NIR spectrophotometry and cyclic voltammetry. The best films produced by anodic electrodeposition on indium tin oxide coated glass substrates have solar transmittance of 0.82 and 0.22 in the bleached and colored state, respectively. Corresponding optimum values for films produced by colloidal precipitation are 0.82 and 0.47. An O-H stretch at 3647 cm<SUP>-1</SUP> corresponding to Ni(OH)<SUB>2</SUB> was found for both anodic and colloidal deposited films in the reduced state. In the oxidized state a stretch was identified at 564 cm<SUP>-1</SUP> characteristic of NiOOH.