Boosting coloration efficiency in an electrochromic device using an ITO/Ag/ITO multilayered electrode and porous WO₃ chromic layer

Figures & data

Table 1. Detailed deposition parameters for each layer of ECD.

Target	Ar: O2	Working pressure (Pa)	Power (W)	Thickness (nm)
ITO	10: 0.1	0.3	100	40
Ag	10: 0	0.3	105	13
				15
				17
				19
W	45: 5	1.0	80	450
		1.5
		2.0

Figure 1. Evolution in the SEM and AFM surface morphologies of the Ag film deposited on the ITO/Si substrate as a function of Ag deposition time (t_dep): t_dep = (a)–(e) 13 s, (b)–(f) 15 s, (c)–(g) 17 s and (d)–(h) 19 s.

Figure 2. Variations in XRD patterns of IAI films inserted with Ag films of varying thickness.

Figure 3. (a) Resistivity, carrier concentration of the IAI multilayers as a function of Ag thickness. (b) Optical transmittance spectra of the IAI multilayers as a function of Ag thickness. (c) Figure of merit and sheet resistance of the IAI multi-layer structures as a function of Ag thickness.

Table 2. The sheet resistance, optical transmittance, and the figure of merit of the IAI multilayers with Ag deposition time varying from 0 s to 19 s.

Thickness of IAI stack (nm)	Ag thickness (nm)	Ag deposition time (s)	Sheet resistance (Ω/sq)	Transmittance (%)	FOM (10^−3/Ω)
80	0	0	135.4	95.7	4.8
93	13	13	169.9	64.2	0.7
95	15	15	16.7	90.9	23.1
97	17	17	14.7	82.3	9.7
99	19	19	11.3	66.6	1.5

Figure 4. CV characteristics of the ECDs with (a) single ITO and (b) IAI-15 s bottom electrodes. The 5th cycle test result was inserted, and the scan rate during the CV measurements was 50 mV/s. (c) Optical transmittance spectra of ECDs with single and IAI-15 s bottom electrodes in the colored and bleached states under sweep voltages of ±1.0 V after 5 cycle loadings. (d) CA characteristics of both ECDs under a sweep voltage of ±1.0 V after 5 cycle loadings. The negative and positive currents represent the coloring and bleaching process, respectively.

Figure 5. Plan-view and cross-sectional SEM images for the WO₃ films prepared at different sputtering pressures: (a)–(d) 1.0 Pa, (b)–(e) 1.5 Pa and (c)–(f) 2.0 Pa.

Figure 6. Measured XRR data for the WO₃ films on the SiO₂/Si substrate under different P_chamber conditions of 1.0, 1.5 and 2.0 Pa. Inset shows an enlarged graph of the XRR spectra.

Figure 7. XPS spectra of W 4f for the films deposited at (a) 1.0 Pa, (b) 1.5 Pa, (c) 2.0 Pa, and (d) the O/W ratio as a function of sputtering pressure.

Figure 8. (a)–(c) Cyclic voltammograms and (d)–(f) corresponding results on optical transmittance results.

Figure 9. (a) Variation in the optical density difference (ΔOD_λ) with respect to the wavelength. (b) Coloration efficiency of WO₃ films at different P chamber conditions of 1.0, 1.5 and 2.0 Pa. (c) The current density corresponding to the process of the response time.

Table 3. Device performance comparisons of ECDs with WO₃-based EC materials.

Composition and phase	Preparation method	ΔT (%)	Tc/Tb (s)	CE (cm^2/C)	Ref.
Porous a-WO3	Magnetron sputtering	86.2 (600 nm)	16/5.7	67.1	This work
Nanocrystal-in-glass structure WO3	Vacuum evaporation	92 (633 nm)	16/11	61.8	[47]
WO3@Ag-nanowires core-shell structure	Hydrothermal	72 (550 nm)	11/8	78.6	[48]
h/o-WO3 nanoparticles	Inkjet printing	75.4 (633 nm)	10/13	131.9	[25]
WO3 nanosheets	Casting	62.57 (700 nm)	10/7	–	[49]
WO3 core/shell nanorod	Spin coating	67.7 (800 nm)	21/15	101	[50]
P8W48/W18O49 nanowires	Self-assembly	61.4 (1060 nm)	86/78	121.0	[51]

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