Absorption and electrochromic modulation of near-infrared light: realized by tungsten suboxide

In the present study, needle-like tungsten suboxide W 18 O 49 nanocrystals were fabricated as the optical active substance to realize the aim of optical control of near-infrared light. The W 18 O 49 nanocrystals were selected in this regard due to their unique optical performance. As revealed by the powder absorption result, the needle-like W 18 O 49 nanocrystals show strong and wide photoabsorption in the entire near infrared region of 780-2500 nm, from which thin films with the W 18 O 49 nanocrystal coating thus benefits and can strongly shield off almost all near infrared irradiation, whereas transmitting the majority of visible light. To make it more tunable, the W 18 O 49 nanocrystals were finally assembled onto an ITO glass via the layer-by-layer strategy for later electrochromic investigation. The nanostructured architectures of the W 18 O 49 nanocrystal electrochromic films exhibit high contrast, faster switching response, higher coloration efficiencies (150 cm 2 C −1 at 650 nm and 255 cm 2 C −1 at 1300 nm), better long-term redox switching stability (reversibility of 98% after 500 cycles) and wide electrochromic spectrum coverage of both the visible and infrared regions. In this study, we combined two features of full-spectrum NIR absorbing materials and NIR-responsive electrochromic windows in a single material.