Preparation And Properties Of Polythiophene-based Electrochromic Composites

Electrochromic materials are a new type of material that can reversibly and continuously change its optical properties through electrochemical reactions.The reversible change in appearance makes it one of the important branches of smart materials.In recent years,conductive polymer-type electrochromic materials have become the focus of current research due to their many advantages.Among them,poly?3,4-ethylenedioxythiophene??PEDOT?is a very promising material as a five-membered heterocyclic conjugated polymer.In this paper,two kinds of electrochromic composites are developed with PEDOT as the main research object,and semi-solid laminated transmission electrochromic devices are designed and assembled.Their structural morphology and electrochromic performance are tested and compared analysis.The details are as follows:1. A poly?3,4-ethylenedioxythiophene?:poly?styrenesulfonic acid?/graphene oxide composite electrochromic material was prepared by in-situ polymerization.The good electrical conductivity of graphene oxide increases the peak current density and intercalation area of the film,and enhances the charge transfer between active ingredients,so that the composite material has good electrochromic properties.Graphene oxide's high specific surface area sheet structure provides a large number of active sites for PEDOT:PSS to promote stronger contact between the electrochromic film and the conductive substrate and better film formation.At the same time,electron and ion implantation/extraction process in redox can be better completed.Therefore,the electrochromic film exhibits an excellent electrochromic performance which is a reversible color change from light blue to dark blue.Compared with PEDOT:PSS film,PEDOT:PSS/GO film has a wider range of discoloration??T=34.94%?,a larger lithium ion diffusion coefficient(2.95×10^-15 cm² s^-1),and a shorter response time?Coloring response time/fading response time are 1.27s/2.5 s?and higher coloring efficiency?172.08 cm²/c?.2. A poly?3,4-ethylenedioxythiophene?:poly?styrenesulfonic acid?/tungsten trioxide composite electrochromic material was prepared by the blending method.The composite material can overcome the self-defects such as a single inorganic electrochromic color change,a long response time,and difficulty in forming a substrate of an organic electrochromic material,and maximize mutual promotion to improve the electrochromic performance.The good film-forming and dispersing properties of tungsten trioxide sol and the effect of adsorbing water between clusters reduce the interface barrier between the thin film and the electrolyte solution,thereby facilitating the diffusion and transmission of ions in redox.In addition,the loose multi-chain structure of the composite material increases the effective contact area between the film and the electrolyte,and also shortens the electron/ion transfer path,which is beneficial to the penetration and transport of the electrolyte.Compared with PEDOT:PSS film,PEDOT:PSS/WO₃ film has wider optical contrast??T=28.98%?,higher ion diffusion coefficient(4.81×10^-15 cm² s^-1),and shorter response time?Coloring response time/fading response time are 2.37 s/2.3 s?and higher coloring efficiency?131.47 cm²/c?.3. The semi-solid layer transmission type electrochromic device was designed and assembled by using the prepared PEDOT:PSS/WO₃composite material.The semi-solid electrolyte promotes the redox reaction of the electrochromic material,enhances the lithium ion injection/extraction process in the entire electrochemical reaction,and makes the device have a stable and durable"memory effect"and a stable color changing process at low voltage.It has considerable prospects in reducing power consumption and saving energy.The results show that the device has a wide range of discoloration??T>35%?,stable coloring/fading state and good cycle stability??T reduction at 75v%WO₃ is about 7.4%?...