Chemical and Optical Studies of Electrochromic Hydrated Nickel Oxide Films and Devices

Over the last few years, hydrated nickel oxide or hydroxide has gained interest as an electrochromic material. It has many important features. First it shows a transparent to bronze coloration which is suitable for a number of architectural, vehicle and aerospace glazing applications. This material is stable in an alkaline environment and colors and bleaches at potentials below 1.0V and below the oxygen and hydrogen evolution potentials. It can be deposited by a wide range of processes, including anodic and cathodic electrodeposition, r.f. and d.c. sputtering, vacuum evaporation, chemical vapor deposition, andssolgel processes. In this work we will discuss films made chiefly by anodic electrodeposition. Some of the best characteristics are seen in films made by electrodeposition. The properties of films made by other deposition processes will be discussed in subsequent chapters. Much of the electrochemical knowledge about hydrated nickel oxide comes from studies of metallic nickel electrodes used in batteries. The study of hydrated nickel oxide based electrochromic devices is just emerging, and so far very few devices have been reported. Some of the work by my group on nickel based devices will be outlined later in this chapter.