Niobium Tungsten Oxides for Electrochromic Devices with Long-Term Stability

There is a keen interest in the use of electrochromic materials because they can regulate light and heat, thereby reducing the cooling and heating energy. However, the long response time, short cycle life, and high power consumption of an electrochromic film hinder its development. Here, we report an electrochromic material of complex niobium tungsten oxides. The Nb18W16O93 thin films in the voltage range of 0 to -15 V show good redox kinetics with the coloration time of 4.7 s and bleaching time of 4.0 s, respectively. The electrochromic device based on the Nb18W16O93 thin film has an optical modulation of 53.1% at a wavelength of 633 nm, with the coloration efficiency of similar to 46.57 cm(2) C-1. An excellent electrochemical stability of 78.1% retention after 8000 cycles is also achieved. These good performances are due to the fast and stable Li-ion intercalation/extraction in the open framework of Nb18W16O93 with multiple ion positions. Our work provides a strategy for electrochromic materials with fast response time and good cycle stability.

Automated summary

This study reports a complex niobium tungsten oxide electrochromic material that exhibits good redox kinetics within a range of polarity, with fast coloration and bleaching times, high optical modulation and coloration efficiency. Moreover, the material demonstrates excellent electrochemical stability, maintaining 78.1% performance retention after 8000 cycles. These superior performances are attributed to the fast and stable Li-ion intercalation/extraction in the open framework of Nb18W16O93 with multiple ion positions, providing a strategy for developing electrochromic materials with fast response time and good cycle stability.