Influence of octahedral ligand field distortions and temperature on the electrochromic response of tungsten oxides

The divergent optical response of WO${}_{3}$$\ensuremath{\cdot}$2H${}_{2}$O compared to anhydrous WO${}_{3}$ represents a critical gap in understanding electrochromic materials. Through combined electronic structure modeling and experimental analysis, the authors demonstrate that structural water molecules fundamentally alter the electronic structure by introducing asymmetries in the tungsten coordination environment. The investigation reveals how these coordination asymmetries, more pronounced in the dihydrate material, create distinct absorption conditions for visible and near-infrared wavelengths that enable independent spectral control. The authors also report on the low-temperature electrochromic response of these materials. By establishing direct correlations between minute structural distortions and macroscopic electrochromic behavior, this work provides mechanistic insight into dual-band electrochromism. These findings advance the fundamental understanding of structure-property relationships in electrochromic oxides and will inform the future of electrochromic materials design.