Electrochromic devices with starch based solid polymeric electrolytes

摘要

The development and applications of durable electrochromic devices (ECD) has gained attention in recent years principally due to the growing use of automobile electrochromic rear view mirrors and electrochromic windows, called "smart windows" in architecture [1,2]. The main advantages of the electrochromic mirrors are the glare attenuation during night conduction and, for windows, the possibility of saving the energy in buildings through the control of sunlight transmission. The ECD's have different compositions and technologies but most of them are based on inorganic materials with WO{sub}3 as electrochromic thin films. There also exist other alternatives like all polymeric solid state electrochromic devices based on modified conducting polymers [3] that change their transmission values from 90% to 50% in 2s. However until now the best results have been achieved with inorganic materials that are now in the focus of several durability tests important for different applications [4]. The electrochromic devices can be made with electrolytes of all-inorganic solid state materials [5], organic based materials [6] or organic-inorganic (ormolyte) based systems [7] that contain mobile species such as lithium or proton [8]. In the case of ormolytes and organic or polymeric based electrolytes, lithium salts are generally used as conductor species. These electrolytes are very interesting because of their lower production cost and more appropriate mechanical properties than inorganic materials [3]. Different solid polymeric electrolytes have been recently proposed based on poly(amide 6-b-ethylene oxide), whose conductivity is in the range of 10{sup}(-4) S/cm at 100°C [6] and natural polymers either grafted hydroxyethycellulose (HEC) [9] or modified starch [10].