Evaluation of Transparent ITO/Nano-Ag/ITO Electrode Grown on Flexible Electrochromic Devices by Roll-to-Roll Sputtering Technology

Abstract

This paper explores the flexible ITO/nano-Ag/ITO multilayer electrodes grown on polyethylene terephthalate (PET) substrates and processed by a continuous roll-to-roll (R2R) sputtering system at room temperature used for flexible electrochromic device (ECD) applications. The effect of the nano-Ag interlayer thickness on the electrical and optical properties of the flexible ITO/nano-Ag/ITO multilayer was thoroughly investigated. By using R2R-sputtered at an Ag DC power of 0.2 kW, we were able to achieve optimal ITO/nano-Ag/ITO multilayer that exhibits a high optical transmittance of 87.19% and the best figure of merit value (30.93 × 10−3 Ω−1). The EC performance and stability of the flexible devices were tested by a cathodic WO3 coloration. Coloring and bleaching tests show that ITO/nano-Ag/ITO multilayers are highly effective conductors, indicating that the R2R sputtering technique is a promising continuous sputtering process in preparing for the fabrication of optical devices and flexible electronics industries.

Optical Properties of ITO/Glass Substrates Modified by Silver Nanoparticles for PV Applications

“…A decrease in mean transmission in the visible region for the ITO/PET layers after the sputtering of the additional silver ion and ITO layers by the continuous roll-to-roll (R2R) sputtering method was also observed by the authors of [32] for the spraying power of 0.05, 0.1, and 0.3 kW. However, the authors [32] obtained an increase in the average ITO/Ag/ITO/PET transmission for 0.15, 0.20 and 0.25 kW sputtering powers. The differences in optical properties of ITO/nano-Ag/ITO/PET multilayers obtained with different sputtering powers authors of [32] explained by the scattering and absorption of the nano-Ag interlayer.…”

“…However, the authors [32] obtained an increase in the average ITO/Ag/ITO/PET transmission for 0.15, 0.20 and 0.25 kW sputtering powers. The differences in optical properties of ITO/nano-Ag/ITO/PET multilayers obtained with different sputtering powers authors of [32] explained by the scattering and absorption of the nano-Ag interlayer. According to the authors [32], the optical transparency can be improved at a certain nano-Ag thickness (corresponding to certain DC Ag powers) on the ITO/nano-Ag/ITO structure.…”

“…The optical properties of ITO thin films strongly depend on the thickness of the film, the deposition parameters, the substrate temperature, the microstructure, the levels of impurities, and dopants or post-growth treatment [21][22][23][24][25][26][27][28][29][30][31]. A decrease in mean transmission in the visible region for the ITO/PET layers after the sputtering of the additional silver ion and ITO layers by the continuous roll-to-roll (R2R) sputtering method was also observed by the authors of [32] for the spraying power of 0.05, 0.1, and 0.3 kW. However, the authors [32] obtained an increase in the average ITO/Ag/ITO/PET transmission for 0.15, 0.20 and 0.25 kW sputtering powers.…”

“…The differences in optical properties of ITO/nano-Ag/ITO/PET multilayers obtained with different sputtering powers authors of [32] explained by the scattering and absorption of the nano-Ag interlayer. According to the authors [32], the optical transparency can be improved at a certain nano-Ag thickness (corresponding to certain DC Ag powers) on the ITO/nano-Ag/ITO structure. The ITO/nano-Ag/ITO/PET multilayer had the highest average optical transmittance at a nano-Ag layer thickness of 6 nm but increasing the nano-Ag thickness above 7 nm reduced light transmittance because the excessively thick Ag layer caused light scattering, particularly in the high wavelength area [32].…”

“…According to the authors [32], the optical transparency can be improved at a certain nano-Ag thickness (corresponding to certain DC Ag powers) on the ITO/nano-Ag/ITO structure. The ITO/nano-Ag/ITO/PET multilayer had the highest average optical transmittance at a nano-Ag layer thickness of 6 nm but increasing the nano-Ag thickness above 7 nm reduced light transmittance because the excessively thick Ag layer caused light scattering, particularly in the high wavelength area [32]. In the case of our layers with a thickness of 5 nm, the authors observed deceleration of the decrease in transmission with the layer thickness, excluding the Ag/ITO3/glass sample (Figure 2).…”