Investigation On Preparation And Properties Of Nickel Oxide Film By Sol-gel Process

Electrochromic(EC) film materials have the special performance of continuous and reverse photoelectric property. They are one of functional materials,which have very good application fucture. It can be used widely in large-area display, light switch, glare—free mirror, deposited devices, building glass and smart windows. The representative of anticathode materials is nickel oxide which is employed as an anodic electrode in conjunction with electrochromic tungsten oxide as colouring electrode. The nickel oxide films can be uses as electrochromic layer and ion storage layer of electrochromic device.In this paper, nickel diacetate is used as sol precursor, nickel oxide thin film on the ITO substrates can be successfully prepared by dip—coating method The influence of the consistency of solution,additive, aging time and the number of the coatings to films' quality are discussed. By using UV—visible spectrophotometer, scan electron microscope and X—ray diffraction, the influences of the process treatment on the electrochromic character and structure of the films are discussed. The change of optical quality , structure in the process of electrochromism and electrochromic mechanism are investigated. The color of colored state and bleching state of films are the chang from palm black to transparence. Actually, the change is the transform of Ni²⁺/Ni³⁺. X—ray photoelectron spectroscopy shows the height change of Ni²⁺ and Ni³⁺, when the films are in the original state , state and bleching state. which can indicate the the transform of Ni²⁺/Ni²⁺.The experiments were carried out: to compare the visible light transmittance of the colored state and bleching state of the electrochromic films, to count the dynamic optial density change , and to test the I—V relations of these films' electrochromic cycles. The outcomes indicates: in the paper, the electrochromic performance are shown in the thin films which have little business with the sol consistency. The nickel oxide films below 250℃for two hours is amorphous,crystalline temperature is between 250℃and 300℃.the amorphous films have better electrochromic performance than those of crystalline ones. During the limit of visible spectrum, the transmittances difference of some samples reached nearly 50%. By the hoist of the annealed temperature and thermal time, the structure of the films can be changed which can worsen the electrochromic character. With the increasing of the number of the coatings , the films can not only improve storage ability to contain ion, but also get better electrochromic character. The nickel oxide films have good electrochromic character in the 1mol/L KOH electrolyte. To improve the consistency of electrolyte,the transmittance of the colored state of the samples are low. that is good electrochromic character.The electrocemical cyclic voltammetric experiment indicate: the nickel films have better electrocemical activity. Heating treament can impair the electrochromic character. The process of the films' coloring is diffusing control.