Organic Ligand‐Free Scalable Dual‐Band Electrochromic Smart Windows

Dual‐band electrochromic (DBEC) smart windows are an emerging energy‐saving technology, especially those constructed from single‐component DBEC materials as they offer an easy way to independently regulate visible (VIS) and near‐infrared (NIR) light. However, the current complicated organic ligand approach used to synthesize single‐component DBEC materials necessitates a post‐annealing treatment, which may severely compromise the scalability of DBEC smart windows. Herein, one organic ligand‐free process is developed to produce well‐controlled Nb‐doped anatase TiO2 nanocrystals (NTO NCs) followed by spraying on arbitrary substrates, giving NTO rigid or flexible films with good DBEC properties and a high optical modulation over 92%. A prototype of a 20 cm × 20 cm DBEC smart window is built. The simplicity and scalability of the synthesis and fabrication process make it a scalable approach to constructing large‐area electrochromic smart windows and foils, with promising applications in fields such as buildings and automobiles. A one‐step hydrothermal method is proposed for synthesizing niobium‐doped titanium dioxide nanocrystals (NTO NCs), offering a scalable and organic ligand‐free approach to produce high‐quality, single‐component dual‐band electrochromic nanocrystals. The prepared NTO NC film exhibits good dual‐band electrochromic performance and high optical modulation of over 92%, holding great potential for large‐scale applications in energy‐efficient buildings and vehicles.