A flexible and high-performance electrochromic smart window produced by WO3/Ti3C2Tx MXene hybrids

Abstract

Tungsten oxide (WO₃) is currently the most popular electrochromic (EC) material for EC devices due to its excellent electrochemical stability and EC reversibility. However, WO₃ generally has low conductivity, causing a high charge transport barrier; consequently, the EC devices based on WO₃ have long coloration/bleaching response time, low optical density, and low coloration efficiency. In this work, we demonstrated that the introduction of two-dimensional titanium carbide (2D Ti₃C₂T_x), a member of MXene, with excellent electrical conductivity leads to a significantly reduced charge transport barrier within WO₃-based EC devices. The EC device based on the WO₃/2D Ti₃C₂T_x hybrid film fabricated by the spray-coating method exhibits a significantly enhanced EC performance with an optical modulation of 57.61% and a coloration efficiency of 126 cm² C⁻¹. Interestingly, the switching response time is 1.5 s for bleaching and 2.7 s for coloration, and is 46.8% (for bleaching) and 62% (for coloration) shorter than the bare WO₃-based EC device. Besides, a large-sized flexible smart window with an area of 15 cm × 15 cm is successfully fabricated and demonstrated. Our results provide insights into the effects of coupling WO₃ and Ti₃C₂T_x to construct an outstanding EC device for smart window applications.