Amorphous and Crystalline Ti-Doped WO3<middle dot>2H2O for Dual-Band Electrochromic Smart Windows

The dual-band electrochromic smart windows (DESW) can selectively modulate visible (VIS) and near-infrared (NIR) transmittance, which is expected to effectively reduce building energy consumption. However, the complex preparation of dual-band electrochromic materials has restricted the further development of DESW. In this work, amorphous and crystalline Ti-doped WO3 center dot 2H(2)O (TiWH) were synthesized by a simple precipitation method, which does not require strict control of the oxygen content and temperature. Ti doping reduced the crystallinity of WO3 center dot 2H(2)O and increased the specific surface area. 3% TiWH films exhibited excellent dual-band electrochromism with high transmittance modulation (633 nm: 83.8%, 1050 nm: 72.5%), fast response time (bleached/colored time: 14.9/15.3 s at 633 nm, 16.0/3.5 s at 1050 nm), good coloration efficiency (633 nm: 22.8 cm2 C--1,C- 1050 nm: 90.8 cm(2) C-1), and high capacitance of 47.1 mF cm(-2) at 0.1 mA cm(-2). The electrochromic device can still maintain good dual-band electrochromism (bright, cool, and dark modes). The excellent dual-band electrochromism and energy storage make TiWH have a good application prospect in green buildings.