Extremely fast electrochromic supercapacitors based on mesoporous WO3 prepared by an evaporation-induced self-assembly

Mesoporous metal oxides consisting of fully interconnected network structures with small pores (20–50 nm) have high surface areas and decreased ion intercalation distances, making them ideal for use in high-performance electrochromic supercapacitors (ECSs). Evaporation-induced self-assembly (EISA), which combines sol–gel chemistry and molecular self-assembly, is a powerful method for the fabrication of mesoporous metal oxides through a solution phase synthesis. Herein, we introduce ultrafast sub-1 s ECSs based on an amorphous mesoporous tungsten trioxide (WO 3 ) that is prepared by EISA. Compared to that of a compact-WO 3 film-based device, the performances of an ECS with mesoporous WO 3 exhibits a large optical modulation (76% at 700 nm), ultrafast switching speeds (0.8 s for coloration and 0.4 s for bleaching), and a high areal capacitance (2.57 mF/cm 2 ), even at a high current density (1.0 mA/cm 2 ). In addition, the excellent device stability during the coloration/bleaching and charging/discharging cycles is observed under fast response conditions. Moreover, we fabricated a patterned mesoporous WO 3 for ECS displays (ECSDs) via printing-assisted EISA (PEISA). The resulting ECSDs can be used as portable energy-storage devices, and their electrochromic reflective displays change color according to their stored energy level. The ECSDs in this work have enormous potential for use in next-generation smart windows for buildings and as portable energy storage displays. Photonics: Smart windows and energy storage Networks of tiny holes improve the energy storage properties of materials that can also be used for smart windows. In electrochromic materials, the fraction of light passing through the material can be controlled using an electrical voltage. This is useful for smart windows which electrically switch from being transparent to opaque. This change is associated with the storage or release of energy, so the same materials are being investigated for energy storage. Keon-Woo Kim from Pohang University of Science and Technology, South Korea, and co-workers have developed an improved electrochromic supercapacitor made from tungsten trioxide. They used an evaporation-induced self-assembly process to deposit a film of tungsten trioxide containing pores approximately 30 nanometers across. This porous structure increased the material’s switching speed and capacitance compared to a conventional tungsten trioxide thin film. Ultra-fast electrochromic supercapacitor