Compositional Optimization of Sputtered WO₃/MoO₃ Films for High Coloration Efficiency

Thin films of mixed MoO₃ and WO₃ were obtained using reactive magnetron sputtering onto ITO-covered glass, and the optimal composition was determined for the best electrochromic (EC) properties. A combinatorial material synthesis approach was applied throughout the deposition experiments, and the samples represented the full composition range of the binary MoO₃/WO₃ system. The electrochromic characteristics of the mixed oxide films were determined with simultaneous measurement of layer transmittance and applied electric current through the using organic propylene carbonate electrolyte cells in a conventional three-electrode configuration. Coloration efficiency data evaluated from the primary data plotted against the composition displayed a characteristic maximum at around 60% MoO₃. Our combinatorial approach allows the localization of the maximum at 5% accuracy.