Fig. 1 Schematic diagram of chromogenic system (a) Al3+ based electrochromic device and its light modulation[11]; (b) Gate-controlled VO2 phase transition by tuning hydrogenating level for high-performance smart windows[12]; (c) Illustration of reversible photochromic reaction in PC-PCN (photochromic porous coordination network)[13]; (d) Schematic description of the adsorption and diffusion of a H atom along WOx based gasochromic thin film[14]

Fig. 2 Schematic diagram (a) and photographs (b-e) of flexible electrochromic device of Ag/W18O49 nanowire co-assemble[17]

Fig. 3 Schematic illustrations of functioning mechanisms for the bi-functional device[18]

Fig. 4 Performance index of the functional layers of inorganic all-solid-state electrochromic device

Fig. 5 Schematic diagram of typical electrochromic device structure[10]

Fig. 6 The key performance evaluation index of typical electrochromic device

Fig. 7 Schematic illustration of the preparation for electrochromic electrodes with and without a graphene interface layer[31]

Fig. 8 Pictures of gel films on FTO glass[32] (a) Immediately after spraying; (b) After 12 h of hydrolysis

Fig. 9 Schematic illustration for the formation of Co3O4 macro- bowl array films[33]

Fig. 10 Synthesis of Nb2O5 thin films grown by single source precursor CVD[34]

Fig. 11 Ag/W18O49 nanowire co-assembles prepared by L-B technique[17]

Fig. 12 Schematic diagram of the fabrication process of the hybrid electrochromic electrode based on self-forming crackle pattern technology[35]

Fig. 13 Ag grid/PEDOT hybrid flexible eletrode film[36] (a) Schematic illustration of the structure of the silver grid/PEDOT:PSS hybrid film; (b) Low- and high-magnification SEM image of the hybrid film; (c) EDS mapping of the hybrid film, demonstrating the uniform distribution of PEDOT:PSS across the whole film

Fig. 14 Scheme of a new ESS window device system (a) and schematic for the device preparation process (b)[16]

Fig. 15 Transmittance and optical modulation changes of the WO3 on the silver grid/PEDOT:PSS hybrid film in the bleached and colored state[36] (a,b) Under repeated compressive bending; (c,d) Under repeated tensile bending. Curvature radius is 20 mm

Fig. 16 SEM cross-section image of ECD-fresh: Glass/ITO/ WO3/LiTaO3/NiO/ITO[52]

Fig. 17 SEM cross-sectional images (a-b) of ECD-1 and ECD-2 with and without the embedment of Ta2O5 layers[53]

Fig. 18 Electrochromic response of W18O49 nanowires under electrochemical insertion from one of the three different ions: Li+, Na+, and Al3+ in organic polycarbonate (PC) solvent using ClO4- as counter ion under ambient conditions[54] (a) CV curves (solid: the 1st cycle, broken: the 30th cycle) of the W18O49 nanowires film at a scan rate of 10 mV·s-1 in 1.0 mol/L PC-Al(ClO4)3, PC-LiClO4, PC-NaClO4; (b) In situ transmittance variation curves between colored and bleached state for W18O49 nanowires film in 1.0 mol/L PC-Al(ClO4)3, PC-LiClO4, and PC-NaClO4. Solid and broken lines are for the 1st and 30th cycle, respectively; (c) Full plot of the in situ transmittance variation in the three non-aqueous solutions, a total of 30 cycles; (d) In situ OD variation as a function of charge density monitored at wavelength of 633 nm in PC-LiClO4, PC-NaClO4, PC-Al(ClO4)3

Fig. 19 Electrochromic performance of WO3 films under various operations[58] (a) Comparison of optical response at 550 nm and for 1.5-4.0 V with and without constant loading current, inset shows a magnified view of the transmittance during 20 initial cycles at 10 mV·s-1; (b) CV data for different cycle numbers at 10 mV·s-1; (c) Trapped and extracted charge densities vs cycle number derived from CV data

Fig. 20 Electrochromic properties of NiO nanoparticles film with seed layer on ITO glass[61] (a) Transmittance spectra of the NiO nanoparticles film with seed layer on ITO glass in the bleached (0.2 V) and colored (0.6 V) states in the wavelength range of 300-900 nm, with inset showing the digital photos of NiO film growing on ITO glass with seed layer on bleached state and colored state; (b) Current response for NiO nanoparticles film at 0.2 and 0.6 V applications in 1 mol/L KOH for 30 s per step; (c) Corresponding in situ optical responses of NiO films for 30 s per step measured at 550 nm; (d) Cycle performance of the NiO nanoparticles film measured in 1 mol/L KOH for 5000 cycles

Fig. 21 LixNiOy all-solid-state ECDs based on gradient Li+ distribution and its performance (a) Schematic diagram of Li ions transportation in the ECD-1 for the coloration process; (b) Schematic diagram of Li ions transportation in the ECD-2 for the coloration process; (c) Comparison of the transmittance variety at 670 nm of LixNiOy-based ECD and NiOx-based ECD at 2.5 V bias; (d) Comparison of this work with recently reported all-solid-state ECDs

Fig. 22 Schematic representation for the LBL fabrication of the multilayered (LDH/PB)n electrochromic film[63,64]

Fig. 23 All-solid-state electrochromic devices developed by our research group