High performance electrochromic device based on multifunctional hydrogel

With the world facing the global warming, air pollution, resource shortages, people pay more attentions to the protection of the environment, saving resources and the development of clean energy. Smart electrochromic windows that used for building exterior wall will largely reduce building energy consumption, which can regulate heat entering the building by controlling the transmittance of light, thereby reducing the consumption of air conditioning and lighting equipment. Electrochromic device (ECD) refers to the external alternating electric field that controls the ion movement inside the device to change the microstructure, and then changes the light transmittance of the device within a certain wavelength, showing color change in appearance. In this paper, a triple-layered ECD based on multifunctional hydrogel is proposed, which consists of hydrogel layer, electrochromic layer and electrode layer. The single hydrogel layer simultaneously processes good conductivity and high ion mobility, replacing the conductive layer, ion storage layer and electrolyte layer in traditional ECD, which simplify the device architecture and then greatly reduce the production cost. The transmittance of hydrogel is about 95%, which greatly improves the transmittance of the transparent state of the device, in favor of the better performance. Amorphous tungsten trioxide (WO3) was used for the EC layer, prepared by sol-gel method. Compared with magnetron sputtering and electrochemical deposition, this sol-gel method is more simple, lower cost and more stable material properties. The assembled ECDs have 80% contrast at a wavelength of 800 nm at a voltage of -2.8 v, which is higher than most ECDs. For the characteristic of light transmittance modulation of electrochromic devices, which can be used in intelligent chromic window, reflector mirrors, display equipment and so on. This proves a way to develop an electrochromic device with high contrast, low production cost and fast response time.