Preparation And Exploration Of All Solid State Electrochromic Film Devices Based On WO₃ And NiO_x

Electrochromic is the phenomenon that the optical properties(transmittance,absorption,reflectance,etc.)of materials change reversibly under the drive of the electric field.Its products are mainly used as "smart windows" for buildings and transportation vehicles,and also have wide application space in information display,spacecraft surface thermal control,military camouflage and other fields.However,due to the problems of high manufacturing cost and single function,the actual application scenarios are mostly demonstration projects or high-end military equipment,which is difficult to popularize on a large scale.In addition to optimizing the inherent properties of electrochromic materials,looking for a cheaper and easier preparation method.It is a solution of doing more with one stroke to realize the combination of electrochromic and other functions to form a multi-purpose integrated device.This article aims to explore the multi-functionalization of electrochromic applications.By preparing PET/AgNWs/ITO films,the influence of sputtering parameters on the optical and electrical properties of flexible composite electrodes is investigated;By preparing PET/AgNWs/ITO/WO3 and PET/AgNWs/ITO/NiOx thin films,the application potential of WO3 and NiOx prepared by magnetron sputtering in the flexible electrochromic field is investigated;By preparing Glass/FTO/Li4Ti5O12 thin films,the electrochromic properties of the zero-strain cathode material lithium titanate in the energy storage batteries field is investigated;By preparing all-solid inorganic PET/AgNWs/ITO/NiOx/LiNbO3/WO3/ITO and Glass/FTO/Li4Ti5O12/LiNbO3/NiOx/ITO electrochromic devices,the electrochromic properties of these two types of devices were studied.A flexible PET/AgNWs/ITO composite electrode was prepared by magnetron sputtering.By optimizing the sputtering parameters,a flexible substrate with a sheet resistance of less than 40 ?/sq and a transmittance of greater than 70%at 550 nm was obtained.Then,WO3 and NiOx films are prepared on the optimized substrate to obtain flexible electrochromic films with excellent performance.For WO3 film,the transmittance modulation at 550 nm is 57.4%,the coloring and bleaching efficiency is 27.79 cm2/C and 40.45 cm2/C,the coloring and bleaching response time is 10.4 s and 9.9 s,the optical modulation is still more than 40%after 500 cycles and 2000 bends.For the NiOx film,transmittance modulation is no significant decline in the 200 cycles CV test.The bleaching time is only 5.7 s,and the coloring time is 11.7 s.In addition,it is found that the scan rate is positively correlated with the polar current density and the average coloring/bleaching efficiency.When the scan rate was 100 mV/s,the average coloring/bleaching efficiency of the film was as high as 99.3 cm2/C,but the charge density is significantly reduced,which means that the reaction is incomplete.This shows that simply pursuing high coloring/bleaching efficiency is not the best choice.Only finding the balance point between high coloring/bleaching efficiency and reaction time can make the film work better.Finally,a flexible all-solid inorganic ITO/NiOx/LiNbO3/WO3/ITO electrochromic device was prepared on the PET/AgNWs substrate by continuous magnetron sputtering without breaking vacuum.The CA and CV tests have proved that it is stable and usable in both power-up modes,and has extremely long cycle durability.The lithium titanate thin film prepared by the mature sol-gel spin coating method in the lithium ion battery process has high transparency and good crystallinity.With the number of deposited layers increases,the crystal structure of Li4Ti5O12 does not change,but the grain size grows.And the dense and uniform surface begins to appear larger nanoporous,its aggregation occurs in LTO-5.Although the nanoporous on the surface of the film are conducive to the movement of ions,excessive defects will cause their cycle life to decline rapidly.In the CV test,the optimal scan rate for the sample is 20 mV/s,and the voltage range expands with the thickness of the active layer.Excessively fast scan speed and too small voltage will make the reaction incomplete.In the CA test,the coloring process may be divided into two stages of reaction.The first stage is the main step,which determines the transmittance modulation and response time.Under optimal parameters,lithium titanate film with large transmittance modulation in the visible region(45%at 550 nm)and near infrared region(80%at 1000 nm)is obtained without decline after 20,000 s cycle,and its coloring and bleaching response time is 19.1 and 8.9 s,respectively.These data confirm that Li4TisO12 is feasible as an electrochromic material.Finally,the lithium titanate film is used as the cathode electrochromic layer,and all-solid-state inorganic Glass/FTO/Li4Ti5O12/LiNbO3/NiOx/ITO devices is successfully prepared,and their electrochromic properties are tested,showing certain dual-band modulation potential and Excellent cycle life.