Study Of Electrochromic Devices Based On Tungsten Oxide Thin Films

Electrochromism refers to the phenomenon in which the material changes color with the injection/extraction of conductive particles under the action of an applied electric field.The electrochromic smart window made of electrochromic material has the characteristics of warm insulation and adjustable light transmittance,and it is expected to replace the traditional glass window in the future.WO₃ is a cathode electrochromic material with a large reserve and low price.The electrochromic device made of the same has the characteristics of large optical modulation range and long color retention time,and has received extensive attention.Due to its stable structure and good cycle stability,crystalline WO₃ has great prospects for its application in electrochromism.In this paper,the optical and electrical properties of electrochromic devices were tested by UV-Vis spectrophotometer and digital source meter.The effects of annealing temperature,AMT and PEI ratio,excitation voltage and film thickness on the electrochromic properties of the devices were further studied.The effect of excitation voltage on device performance was studied.The results show that the optical modulation range of electrochromic device increases first and then decreases with the increase of excitation voltage,which is the largest at±2.1V.Studying the influence of annealing temperature on the optical modulation range,it is shown that as the annealing temperature increases,the internal defects of the crystal particles decrease,so that the ions can not enter the deeper part of the crystal,which reduces the effective color changing unit,and the optical modulation range is gradually reduced.However,the conductive ions can penetrate deeper into the crystal in the case of more crystal defects,but the time spent will be longer,resulting in a longer response time as the annealing temperature increases.The effect of AMT and PEI ratio on device performance was studied.The results show that as the relative content of AMT increases,the WO₃ film becomes denser and denser,which increases the effective color change unit and makes the light modulation range gradually increase.Based on the analysis of the experimental results,the parameters were optimized,and the optimal parameters were prepared.The performances were as follows:in the near-infrared region?850 nm?,the optical modulation range was 42.2%,the coloring time t_c was 30 s,and the fading time t_b was 164s,color retention is good,the transmittance change is only 0.9%within 1 hour after the coloring state is cut off,the cycle stability is relatively good,and the peak current changes little.