Characterization of an all solid-state electrochromic window

Abstract

Sol-gel cerium - titanium oxide layers present potential application as transparent counter-electrode (ion storage layer) in electrochromic windows and mirrors using lithium conducting electrolyte and WO3 electrochromic coating. The precursor sol, prepared by mixing Ti(OPr1)4 and Ce(NO3)6 (NH4)2 in ethanol, is initially dark red and becomes transparent after a few days aging indicating the presence of Ce3+ complexes. The layers have been obtained by dip coating technique and heat treated at 450°C during 15 minutes. They have been characterized by XRD, SIMS, optical absorption and electrochemical techniques; it is shown that the electrochemical reaction corresponds to a reversible insertion-extraction of lithium ions within a TiO2 amorphous film containing small CeO2 crystallites. At low sweep frequencies the process is controlled by a diffusion mechanism (DLi approximately 6.4 10-12cm2/s at 25°C). Characterizations of an all solid state electrochromic window/glass/ITO/WO3 POE-Li N (SO2 CF3)2/TiO2 - CeO2/ITO/glass/are also presented.