Niobium and Fluorine Dually Doped Titanium Oxide Nanosheet Arrays for Selective Dual-Band Electrochromic Applications

Dual-bandelectrochromic (EC) films selectively modulating visible(VIS) and near-infrared (NIR) light promise an attractive option forefficiently utilizing solar energy. Anatase titanium dioxide (TiO2) promises dual-band EC capability; however, it suffers fromthe difficulty in circumventing the obstacle in the NIR region andsluggish reaction kinetics as well as poor cycling stability. In thiswork, 2D (Nb, F) co-doped TiO2 nanosheets (NSs) arraysare reported as an effective single-component dual-band EC material.The co-doping can induce an oriented growth of freestanding ultrathinNSs with exposed (001) facets which promote the EC reaction kinetics.The high aspect ratio and orientation of the nanosheets favor thelocalized surface plasmon resonance (LSPR) effect triggered by electrochemicalbias voltages, thus achieving independent modulation of the NIR transmittance.Three application scenarios of the NSs can be presented based on selective,efficient, and high optical modulation in the NIR and VIS regions(79.5% at 700 nm and 78.4% at 1300 nm, respectively), unprecedentedfast bleaching/coloring times (3.0/8.4 s), and a long cycle life (500cycles). Moreover, the films exhibit multi-color EC and energy storagematerials. This work may provide an insight into the single-componentdual-band EC mechanism of 2D TiO2 nanostructures and presentpromising potential for energy saving and smart display applications.