Assessing the Electronic Structure of TaVO_x and Its Electrochromic Performance in Combination with LiPSON

Abstract

In this study, radio-frequency sputtered tantalum vanadium oxide (TaVO x ) films are investigated as a promising material for the ion storage layer in an electrochromic device. Using spectroelectrochemical measurements by cyclic voltammetry, the electrochromic switching properties of the material are presented. The intercalation and deintercalation mechanisms of Li+ ions into TaVO x thin films have been studied by X-ray photoelectron spectroscopy. To obtain information about the composition and electronic structure of the material, films with different degrees of intercalation levels of Li+ ions are studied. The results clarify which species are involved in the electrochromic mechanism. In order to be able to evaluate the stability of electrochemically treated samples, films in the final deintercalated state are also analyzed. It is shown that only vanadium is actively involved in the investigated redox reaction. Finally, TaVO x is integrated with the solid-state electrolyte lithium phosphorus sulfuric oxynitride into a model electrochromic switching cell. Chronoamperometry shows a stable charge transfer of about 27 mC cm–2 combined with suitable values for optical transmittance of more than 70% (at 550 nm). Based on the high stability in terms of charge density and suitable color neutrality, we confirm the general suitability of this material combination for use in electrochromic applications.