Preparation And Properties Of Inorganic Electrochromic Films And Devices

Electrochromism refers to the change of optical properties（such as color,transmittance,reflectivity,etc.）caused by the double injection or extraction of ions and electrons in the material under the action of an applied electric field.Electrochromic materials are widely used in the fields of construction,automobile,national defense,etc.Due to their low driving voltage,low energy consumption,wide adjustment range,and open circuit memory function,and thus developed by electrochromic materials.The electrochromic device is a hot spot of research.However,due to defects in the electrochromic thin film or the device itself,the electrochromic device has a large leakage current during operation,which seriously affects the memory performance of the device,increases the power consumption of the device,and affects the life and stability of the device.Therefore,it is of great theoretical and practical significance to study how to reduce the leakage current in electrochromic devices.Adding a barrier layer（protective layer）capable of blocking electrons in the electrochromic device can effectively reduce leakage current.Because Ta₂O₅ has good dielectric properties,it can be used as a barrier layer for electrochromic devices,and its effects on electrochromic thin films and devices were studied.In addition,the traditional electrochromic materials have a single color and unstable performance,which still restricts their development and application.Therefore,the search for a new type of electrochromic material with excellent performance is an urgent problem to be solved.Lithium manganate materials are widely used in batteries,have the advantages of non-toxicity,rich raw materials,environmental friendliness,etc,and have the advantages of high energy density,good cycle stability,and variable color,and can be used as electrochromic materials.Therefore,lithium manganate film and electrochromic device based on lithium manganate film were prepared and their structure and electrochromic properties were studied.Tungsten oxide and nickel oxide are widely studied electrochromic materials,often used as the cathode and anode of electrochromic devices.In this paper,the magnetron sputtering method was used to optimize the preparation of tungsten oxide and nickel oxide electrochromic thin films by adjusting the process parameters.XRD analysis showed that the prepared tungsten oxide was amorphous and the nickel oxide was crystalline.It was found by SEM analysis that the surface of the tungsten oxide was loose,and the surface of the nickel oxide was flat and the particles were clear.Electrochemical and optical performance tests have found that both films have good electrochromic properties.The barrier Ta₂O₅ film was continuously sputtered on the tungsten oxide and nickel oxide films by magnetron sputtering.Cyclic voltammetry was applied to WO₃ and WO₃/Ta₂O₅ with±1V voltage.It was found that the envelope area of the cyclic voltammetry curve of WO₃ film was significantly larger than that of WO₃/Ta₂O₅ film.The optical properties of the two films were tested and found that the optical modulation amplitude of WO₃ was 75%at 550nm,while the WO₃/Ta₂O₅ film layer had an optical modulation amplitude of only 50%at 550 nm.The cyclic voltammetry test was also applied to the NiO and NiO/Ta₂O₅ with±1V voltages.It was found that the redox peaks of the two were different.The optical properties of the two films were tested and found to be NiO at 550 nm.The optical modulation amplitude was 40%,and the optical modulation amplitude of NiO/Ta₂O₅ film was 38%at 550nm,which indicated that the barrier layer Ta₂O₅ has a great influence on the optical properties of WO₃ film,but has little effect on NiO film.This difference may be caused by the difference in interface between WO₃/Ta₂O₅ and NiO/Ta₂O₅.The structures of prepared by magnetron sputtering were respectively Glass/ITO/NiO/LiNbO₃/WO₃/ITO,Glass/ITO/NiO/Ta₂O₅/LiNbO₃/WO₃/ITO,Glass/ITO/NiO/Ta₂O₅/LiNbO₃/Ta₂O₅/WO₃/ITO three（ie,5,6,7 layer）electrochromic devices.The comparative study found that the optical modulation amplitude of the prepared 6-layer devices in the visible region can reach 59.4%,which was better than 41.5%of the 5-layer devices and 39.8%of the 7-layer devices.Cyclic voltammetry tests show that the 6-layer and 7-layer devices have smaller leakage current and good open-circuit memory performance than the 5-layer devices.A lithium manganate electrochromic film was prepared by spin coating using a sol-gel method.XRD analysis showed that the lithium manganate film was a spinel structure;it was found by SEM analysis that there were many pores on the surface of the film;the electrochemical properties of the film were investigated,and the color of the prepared film was changed between light yellow and orange.The optical modulation amplitude of the film at 500 nm can reach 41.8%,indicating that lithium manganate is a new type of electrochromic material.An electrochromic device with a structure of Glass/ITO/WO₃/UV-based-PC-LiClO₄/LiMn₂O₄/FTO/Glass was prepared by using a lithium manganate film as an electrochromic layer and tungsten oxide as a counter electrode layer.Through electrochemical test analysis,it was found that the prepared electrochromic devices have an optical modulation amplitude of up to 34.9%（at 550 nm）,the coloring time was only 16s at-1.7V¹V,and the bleaching time was 11s.The coloring efficiency of the device up to 57.69 mC/cm².