Transparent tantalum cluster-based UV and IR blocking electrochromic devices

Abstract

The integration by a solution deposition process of tantalum octahedral clusters in multifunctional nanocomposite materials and devices for smart windows is investigated for the first time in this study. Two [Ta₆Brⁱ₁₂]ⁿ⁺ cluster core-based highly transparent visible UV and NIR filters are realized. Films are fabricated by incorporation of clusters in a polymer matrix and coating them on an ITO substrate. The electrochromic cell consists of a Ta₆-based electrolyte inserted between two transparent conductive electrodes. In both cases, the modification of the absorption properties in the visible and NIR spectral range is possible by altering and controlling the oxidation state of the tantalum cluster. The stabilization of reduced [Ta₆Brⁱ₁₂]²⁺ or oxidized [Ta₆Brⁱ₁₂]^3+/4+ species leads to green-emerald or slight brown filters having a slight or a strong red-NIR absorption respectively. Their efficiency in energy saving is estimated by the determination of figures of merit and color coordinates. This highlights that [Ta₆Brⁱ₁₂]ⁿ⁺-based composites are promising absorbers for energy saving applications.