Effect Of Micro-nano Modification Of Electrode Surface On The Electrochromic Performance Of Polymer

Electrochromism refers to the reversible change of optical properties of materials under the applied voltage,which usually shows the change of color.In essence,this phenomenon is that the applied voltage changes the redox states of materials.The materials have different optical properties in the oxidation and reduction states.Conducting polymers have the advantages of good processability,multicolor,easy to design and low cost,which is an ideal choice for a new generation of electrochromic materials.However,due to their low optical contrast,slow response speed and poor cycling stability,the practical application of polymer electrochromic devices(ECDs)is limited.In this paper,silver nanowires(AgNWs),poly(3-thiophene boric acid)(P3TBA)nanoparticles and exfoliated graphene(EG)/AgNWs are respectively modified to the surface of ITO glass,and the effect of micro-nano modification on the clcctrochromic properties of polymer films is investigated.The main research contents arc as follows:(1)AgNWs were synthesized by polol myethod using ethylene glycol and silver nitrate as raw materials,and then dispersed into ethanol to prepare the dispersion.A layer of AgNWs dispersion was evenly coated on the ITO glass by rod-coating method,and the AgNWs/ITO electrode was prepared after drying.Then,the polymer film was prepared by electrochemical polymerization on the AgNWs-modified electrode.The structure and properties of AgNWs and polymer films were characterized by X-ray diffractometer,scanning electron microscope,ultraviolet visible spectrophotometer,electrochemical workstation and device cyclic testing system.The results showed that compared with ECD based on electrochromic polymer(ECP)/ITO,the optical contrast of the ECD based on ECP/AgNWs/ITO increased obviously.After 90 cycles,the optical contrast of ECD based on ECP/ITO decreased significantly,while the optical contrast of ECD based on ECP/AgNWs/ITO was only slightly reduced.Moreover,the ECD based on ECP/AgNWs/ITO had shorter response time and higher coloration efficiency.This indicated that the modification of AgNWs could significantly improve the performance of polymer-based electrochromic devices.(2)A thin layer of P3TBA nanoparticles was first deposited on ITO glass by electrochemical method.After being dried in the air,the ITO glass was inserted into the electrolyte containing thiophene.After polymerization for 60 s,the polythiophene(PT)/P3TBA composite film was obtained.The polymer film was assembled into the ECD and its structure and properties were characterized.As a result,the performance of ECD based on PT/P3TBA/ITO was signifcantly improved,which exhibited a highly optical contrast(48%),coloration efciency(298 cm2/C),short response time(the coloration time and bleaching time are 5.27 and 0.48 s),and stable cycling.Compared with ECD based on PT flm on ITO glass(PT/ITO),the optical contrast of ECD based on PT/P3TBA/ITO increased by 200%(16%?48%),and its coloration efciency increased by 54%(193?298 cm2/C).(3)Graphene nanoflakes were prepared in ammonium sulfate solution by electrochemical exfoliation method.After washing and filtering,EG was dispersed into the mixed solvent of ethanol and water to prepare the dispersion.Then,the AgNWs dispersion was drop-coated on ITO glass.After drying,EG dispersion was sprayed onto the surface of AgNWs-coated ITO substrate.After being dried in the air,the PT/EG/AgNWs composite film was prepared on the electrode by electrochemical polymerization.The polymer film was assembled into the ECD and its structure and properties were characterized.The results indicated that the ECD based on PT/EG/AgNWs/ITO possessed large optical contrast(36%),high coloration efficiency(234 Cm2/C),fast response time(the coloration and bleaching time are 6.63 and 0.71 s),and exhibited stable cycling.In comparison with the ECD based on PT film on bare ITO(PT/ITO),the optical contrast of ECD based on PT/EG/AgNWs/ITO was doubled(18?36%),and its coloration efficiency increased by 42%(165?234 cm2/C).Additionally,we could find that the dynamic processes of bleaching and coloration were all divided into three parts:I,primary stage;II,middle stage;III,late stage.The primary bleaching and coloration were completed in the first two stages.In stage II,the rate constants of bleaching and coloration could be obtained from the linear regression curves.