A novel core–shell TiO2–aWO3 inverse opal structure was fabricated with significantly enhanced electrochromic long term reversibility in NIR region.

and implementation of alternative energy technologies, e.g., renewable energy such as wind turbine and photovoltaics. However, such technologies by themselves are insufficient. Effective management of energy consumption is also crucial in order to properly address the issue of energy shortage. As countries become increasingly developed, the construction of many high-rise buildings quickly follows. Consequently, the smart utilization of solar radiation through glass windows becomes a primary concern. Therefore, smart window technology, an effective energy conservation method, is introduced to assist the reduction of energy consumption of indoor lighting and airconditioning. In this field, electrochromic (EC) materials, which are able to electrically modulate the transmittance of solar radiation, are one of the most widely investigated smart window materials. [1] Various transition metal oxides and conjugated polymers, such as tungsten oxides (WO 3 ), [2] vanadium oxide (V 2 O 5 ), [3] nickel oxide (NiO), [4] polyaniline, [5] and poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), [2c,6] have been studied for this application. Amongst transition metal oxides, WO 3 possesses the best EC effectivity and is thus the focus of many researches to date. The ability of WO 3 to induce color changes was first explored in the early 19th century, while subsequent electrochemical studies began around 1930. [7] It was reported that WO 3 exhibited reversible changes in optical property (colored/bleached) corresponding to the electrochemical insertion/extraction of small cations such as H + or Li + (Equation (1), M = H, Li,…) [8] WO M e MWO 3 bleached 3 colored