3D Pine‐Needle‐Like W₁₈O₄₉/TiO₂ Heterostructures as Dual‐Band Electrochromic Materials with Ultrafast Response and Excellent Stability

Abstract

Dual‐band electrochromic (EC) smart windows, which can selectively modulate visible (VIS) and near‐infrared (NIR) light are widely regarded as one of the most attractive options to drastically reduce energy consumption in modern buildings. However, dual‐band EC smart windows still face many challenges such as weak modulation selectivity between VIS and NIR bands, low switching speed, poor durability, and high cost. Here, inspired by pine needles, a unique pine‐needle‐like (PNL) W18O49/TiO2 heterostructure is rationally constructed with W18O49 nanothorns (as branches) and TiO2 nanofibers (as backbones). The PNL‐W18O49/TiO2 heterostructures exhibit superior dual‐band EC performance in both VIS and NIR bands, which can block up to 81.4% of the VIS light at 633 nm and 91.3% of NIR at 1800 nm, and they also show extremely short bleaching/coloring time (0.9/1.2 s) and excellent stability (85% of capacity retention after 20 000 cycles) in a narrow potential window of −0.8 to 0.6 V. Besides, abundant patterned EC layers on a fluorine‐doped‐tin‐oxide‐coated conductive glass and flexible polyester conductive films can also be realized. This work provides an effective way for dual‐band EC materials’ design and their further development in smart windows and intelligent displays.

Extraordinarily Stable Aqueous Electrochromic Battery Based on Li4Ti5O12 and Hybrid Al3+/Zn2+ Electrolyte

“…The numerous diffusion channels allow fast ion incorporations and extractions from the entire LTO layer, which is extremely important to the fast switching of the electrochromic cell. 36,37 Although the LTO film has a porous microstructure populated with nanotunnels, the root-mean-square surface roughness (R q ) is only 3.25 nm, as confirmed by the AFM image in Figure 1c. Such high level of flatness reduces the scattering of light at the LTO surface, thus enhancing the transparency of the electrode in the bleach state.…”

“…We attribute this to the strong polarization force of Al 3+ on the lattice which weakens the Ti−O−Ti connection between neighboring octahedra, thus resulting in [TiO 6 ] octahedral-tilting distortion (Figure 6d). 37 Generally, the energy gap between the strongly hybridized O 2p orbitals (valence band) and Ti 3d orbitals (conduction band, consisting of degenerate t 2g /e g levels) can reach 3.7−3.9 eV, leading to the observed highly transparent Li 4 Ti 5 O 12 in the visible spectrum. 46 During the coloring process, the Al 3+induced lattice distortion splits the degenerate t 2g /e g into different energy levels, and the electrons supplied by the external circuit fill the 3d orbitals during the reduction of Ti 4+ .…”

Robust and stable dual-band electrochromic smart window with multicolor tunability

“…S4, ESI†). 8,11,52 As shown in Fig. 3g, after 10 000 electrochemical cycles, the integrated charge of the film can remain at 97% of the initial value.…”

“…3–9 In particular, the emerged dual-band electrochromic smart windows (DESWs) developed in recent years can selectively control the transmittance of near-infrared (NIR) solar heat and visible (VIS) light into the building, maximize use of solar radiation, realize a building heating, cooling, and lighting system with the best efficiency and meet the demand of indoor occupant comfort and reducing building energy consumption. 6,10–13 Therefore, developing high-performance DESWs has become an important emerging technology to construct green energy-saving buildings and achieve carbon emission reduction.…”

Constructed TiO 2/WO 3 heterojunction with strengthened nano-trees structure for highly stable electrochromic energy storage device

“…Electrochromism is intimately associated with the double injection of Li + ions and electrons into the WO 3 lattice as Eq. ( 1) [33]:…”