The thin and flexible triple-layered electrochromic device based on the multifunctional hydrogel

Abstract

Electrochromic devices (ECDs) are widely used in smart color changing windows, automotive antiglare rear-view mirrors and electronic wearable devices owing to their controllable for colouration, reduced energy consumption and modulated incident light. Traditional ECDs composed of complicated configurations, commonly five layers of structure, extremely increased the complexity of structure and fabrication process, especially cut down the performance of the device. In this paper, the introduction of hydrogel (The transmittance in the visible light spectrum reached up to 95%), both acted as the conductive layer and the dielectric layer, simplified the structure of the device to a triple-layered one. Flexible electronic products require good flexibility of conductive materials, so we introduced flexible Indium tin oxide (ITO) as the transparent conductive substrate, which have excellent bending properties, the sheet resistance increased only from 12.6 Ω/sq to 31.4 Ω/sq, after 2500 bending cycles. The assembled ECD has a slight transmittance attenuation (ΔTe/ΔT0=7%) after 1500 bending cycles. Importantly, the device showing excellent cycling performance, has just 2% attenuation of transmittance at wavelength of 640 nm, after 1000 cycles (ΔT changes from 32% to 30%), which also has a fast coloration and bleaching time, respectively 3 and 4.7 seconds. Compared with five layered structure, three layered ECDs show prominent advantages, accelerating the development of simple structure electrochromic applications in the future.