Strategic Synthesis of Mixed-Phase Tungsten Oxide for Electrochromic Smart Windows.

Electrochromic devices based on mixed-phase WO can potentially outperform their pure-phase counterparts due to the optimized distribution of optically active sites that facilitate cation intercalation. In this work, we synthesized WO containing orthorhombic and hexagonal phases, with precise phase ratio control accomplished through a meticulously designed experimental strategy of optimizing the reaction time at low temperatures in a closed system under a hydrogen atmosphere. A detailed XRD analysis shows an optimal phase ratio (orthorhombic/hexagonal = 0.