Flexible and High-Performance Electrochromic Smart Window Produced by WO3/Ti3C2Tx MXene Hybrids

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 Ti3C2Tx), 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 Ti3C2Tx 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 Ti3C2Tx to construct an outstanding EC device for smart window applications.