Study On Electrichromism Of WO₃ Thin Films And Devices

The capabilities of tungsten trioxide thin films from r.f. magnetic sputter deposition and smart windows including the film were studied. And making tungsten oxide thin films technics conditions were researched on R. F. sputtering magneton instrument that allows controlling temperature. Oxygen max flux is 50 ml/min in the instrument and the pressure of Ar flux at Ar valve should keep at 1KN. We get W black film under pure Ar sputtering, because sputtered oxygen and tungsten atoms from tungsten oxide target were blocked off by Ar and lost chance of combine each other. Even if oxygen flux was keep at max in sputtering chamber, and mix pressure of Ar and O2 in sputtering chamber was raised, it will mean oxygen reduce relatively and Ar increased relatively. Lacking of oxygen under sputtering, it will get mixed crystal and amorphous films which stoichiomery will departure pure WO3 stoichiometry. We discovered that there are most more WO3 in the films which sputtered in 60W and mix pressure at 4 Pa. We studied the electrochromic performances of mixed films sputtered by r.f magnetic sputter and smart windows involved tungsten oxide thin films under voltage in chapter two. We studied the cyclic voltammetry of tungsten oxide thin films sputtered in 60W and mix pressure at 4 Pa, and optic characteristic of smart windows involved tungsten oxide thin films. We discovered the cyclic voltammetry of tungsten oxide thin films immersed in LB series electrolytes are different from those of tungsten oxide thin films immersed in others electrolytes. They showed the Li+ ions number of charging is as same as the Li+ ions number of discharging, and tungsten oxide thin films still had electrochromism after Li+ completely drop out tungsten oxide thin films without reverse voltage. We cannot explain the electrochromic phenomena of tungsten oxide thin film immersed in LB series electrolytes using the double insertion model and the charge transfer theory. Considering Li+ ions insert just play a promoting action for electrochromise, and In chapter four, On the basis of Ligand Field Theory which is mostly theory to explain transition metal compound electron structure and study transition metal compound physics and chemistry performances, and correlation of Ligand Field with electron orbits of center ions , we explained that oxygen atoms symmetry electric fields was interfered by injecting Li+ ions in tungsten oxide films and they affect W6+ ions d orbitals which five in one, the orbital split were weakened and the difference between eg energy lever and t2g energy lever reduce, which bring absorbable valley at 500nm to red and near infrared area. Considering randomicity of Li+ ions injecting that made tungsten oxide films had continuum intensity absorbable valley in red and near infrared range of visible light。Because AC impedance technique can repeat to measure tungsten oxide films and ITO electrode system in very large frequency range using small swing sin interfere signal which ensure no big changes happening in tungsten oxide films and ITO electrode system during measurement, we can get tungsten oxide films capacitances, resistance, diffuse resistance, capacitances Cdl etc. about tungsten oxide films capabilities information. Due to tungsten oxide films and ITO electrode system in different electrolytes had disaffinity mechanism, it's need to set up different model to deal with tungsten oxide films and ITO electrode systems respectively using AC impedance method. In chapter five we studied impedance performances of ITO plane electrode with tungsten oxide films immersed in LB electrolyte series and in 1 mol LiClO4 propylene carbonate (LIPC) electrolyte respectively. We gained the Equivalent Circuit about the electrode with tungsten oxide films, constant phase angle elements, resistance of tungsten oxide thin films and diffusion resistances and capacitances Cdl, and charges transfer resistances of electrode Rt. On a basis of electrochromic tungsten oxide films research, we try to doped titanium oxide in tungsten oxide films for improving tungsten oxide film electrochromism. At chapter six we study the electrochromic capability, optic capability of titanic oxide doped tungsten oxide thin films and smart windows and impedance of film immersed in 1 mol LiClO4 propylene carbonate (LIPC) electrolyte, We gained the Equivalent Circuit about (1-x)WO3-xTiO2 and ITO electrode system, constant phase angle elements, resistance of (1-x)WO3-xTiO2 thin films and diffusion resistances and capacitances Cdl, and charges transfer resistances of electrode Rt.