Visible Light-Near-Infrared Dual-Band Electrochromic Device

Dual-band electrochromic devices arean important tool formanaging thermal load and energy consumption in buildings. We herein propose a proof of concept of a full dual-bandelectrochromic(EC) device able to selectively modulate solar light between 300 and1600 nm. Dual-band control was achieved by exploiting the complementarityand cooperation of two earth-abundant and nontoxic transition metaloxide nanocrystalline materials able to absorb two different spectralregions when electrochemically charged. The active materials wereobtained through a microwave-based synthetic protocol able to producemassive amounts of ligand-free water-soluble TiO2@WO3-x colloidal heterostructured nanocrystals.The inorganic heterostructures were deposited via a spray-coatingairbrushing method. Graphene was adopted as a near-infrared (NIR)transparent material for the realization of conductive substrates.The nano-dimensions and stable solubility of active materials duringthe deposition process endorse the development of scattering-freenanostructured electrodes and high device transparency under open-circuitconditions, respectively. The spectro-electrochemical properties ofthe as-made nanostructured electrodes were evaluated in relation topure WO3-x and TiO2 singlenanomaterials and a blend of these. The heterostructured architectureensures a lower optical haze (around 8% of total radiation) as againstthe blend, contributing to improving the overall EC performance. TheTiO(2)@WO3-x -based deviceshows 67% NIR shielding while preserving 60% of visible (VIS) transparencyunder cool-mode conditions and 89% screening of VIS and NIR radiationunder the dark mode. These results represent an important step forwardin the development of scalable dual-band EC devices.