Advanced Dual‐Band Smart Windows: Inorganic All‐Solid‐State Electrochromic Devices for Selective Visible and Near‐Infrared Modulation

Abstract Dual‐band electrochromic smart windows (DESWs), capable of actively and selectively modulate visible (VIS) light and near‐infrared (NIR) heat, have emerged as a practical technology for enhancing user comfort and reducing building energy consumption. However, the design and development of DESWs remain a significant challenge due to the difficulty in obtaining suitable materials and high‐durability electrolytes. Here, the first all‐solid‐state DESW based on an orthorhombic oxygen‐deficient tungsten oxide (o‐WO 3‐ x ) film is presented. Benefiting from the synergistic effects of the efficient oxygen‐vacancy‐enhanced charge transfer process and the secure transfer pathway enabled by the orthorhombic crystal structure, the o‐WO 3‐ x film showcases remarkable dual‐band electrochromic properties, including selective modulation of VIS light and NIR heat, large optical modulation (89.1%), rapid response time ( t b / t c = 6.8/17.9 s), high coloration efficiency (155.92 cm 2 C −1 ), and ultrastable cyclic performance (8000 cycles) even in acidic aqueous electrolyte. Furthermore, the all‐solid‐state DESWs incorporating o‐WO 3‐ x deliver a significant and stable dual‐band electrochromic response with excellent thermal regulation and energy‐saving capabilities. These findings underscore the considerable potential of o‐WO 3‐ x films and their all‐solid‐state smart windows in decreasing building energy consumption.