Preparation And Study Of Colorful Flexible Electrochromic Devices

With the rapid development of intelligent electronic display materials,single-function devices can no longer meet people's application requirements,and integrated multi-functional energy storage and conversion devices incorporate novel features and functions in smart and interactive modes,becoming industry and academic hotspots of the community.Electrochromism,as an important technology in the field of intelligence,is gradually attracting people's attention.It can reversibly change the color according to the external voltage,and color is the most intuitive visual perception of people.Integrating sensors of different functions with electrochromism can feedback the external environment or people's own state changes to people.Flexible electrochromic devices have great potential for application in smart wearable and color-changing camouflage.However,how to select suitable electrochromic materials and electrolytes,and how to adjust and control the process conditions of the devices is a problem to be solved in preparing large-area flexible electrochromic devices.In this paper,poly?3-hexylthiophene??P3HT?and poly?3,4-ethylenedioxythiophene?/polystyrene sulfonate?PEDOT:PSS?films were used as the main research objects,polyvinylidene fluoride?PVDF?/ionic liquids?ILs?and polyvinylidene fluoride?PVDF?/1-methyl-2-pyrrolidone?NMP?composite gel electrolytes were prepared.The electrochromic layer and electrolyte were assembled into flexible electrochromic devices by hot pressing,and the electrochromic properties of the device are improved.The main research contents are as follows:PVDF/ILs composite gel electrolyte was prepared with PVDF as polymer matrix,1 mol/L Lithium perchlorate?LiClO4?/Propylene carbonate?PC?as liquid electrolyte and adding ILs with different contents.It was found that the composite gel electrolyte with 50%ILs had the best performance.Its ion conductivity 7.48×10-3 S/cm,and it has a high transmittance of nearly 90%at 525 nm.After 14 days at room temperature,the ionic conductivity decreased by only 20%.The P3HT film prepared by spin coating was assembled into a flexible electrochromic device with a optical modulation range of 20%,a coloring time of 5 s,and a bleaching time of 12 s.The coloration efficiency is as high as 361.0 cm²/C.The device exhibits good electrochromic properties.In order to solve the problem of poor contact between PVDF/ILs composite electrolyte and flexible substrate,a PVDF/NMP composite gel electrolyte with better adhesion to flexible substrate was prepared.It was found that the ionic conductivity?was 2.46×10^-33 S/cm,with a high transmittance in the UV-visible region of 300–800 nm,approximately 80%or more.The electrochromic performance of devices assembled with PVDF/NMP composite gel electrolyte and large-area thin films prepared with P3HT spray solution concentration of 1.8 mg/mL was excellent.The device has a optical modulation range of 17%,a coloring time of 42 s and a bleaching time of10 s,and a coloration efficiency of 302.6 cm²/C.It has a good cycle life and has a certain barrier effect on near-infrared light.It can maintain a certain time of color after power off and also has good electrochromic performance in a bent state.Large-area PEDOT films were prepared as electrochromic layers by screen printing,and assembled into large-area flexible electrochromic devices with PVDF/NMP composite gel electrolytes.The effect of the number of layers of different screen printed PEDOT on the electrochromic properties of the device was investigated.The study found that the screen-printed2-layer PEDOT film has good compactness and high initial transmittance?70%at 645 nm?.The assembled device has a high optical modulation range??T of 31%?,good response time?coloring time is 34 s,bleaching time is 22 s?,high coloration efficiency?CE=702.4 cm₂/C?and certain The cycle stability can maintain a certain color after power off and also has good electrochromic performance in a bent state.