Printing Film On Paper Surface Based On PEDOT:PSS And Its Application In Electrochromic Devices

In recent years,new organic electronic devices have attracted widespread attention due to their low cost and wide range of material selectivity.Electrode material is an important factor affecting the performance of electronic devices.Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)soluti-on has significant advantages due to its electrical conductivity,solution processability and stability,but the conductivity of PEDOT:PSS needs to be improved.PEDOT:PSS solution generally forms conductive films on substrates such as glass and plastic.It is more and more popular to use natural degradable paper as the substrate for forming films with PEDOT:PSS solution.Since PEDOT:PSS film has the characteristics of electrochromic performance and conductivity,it can be used as both the chromic layer and electrode layer of electrochromic devices.It is becoming a trend to fabricate functional layers of electronic devices by printing methods that are easy to process and can be produced in large areas and save cost.In view of the above situation,the main research work of this paper is as follows:Firstly,in order to solve the problem of low conductivity of PEDOT:PSS,the solvent-doped PEDOT:PSS solution was coated on different papers(ink-jet printing paper,sulfuric acid paper,offset paper,copy paper).We explored the relationship between paper properties and the conductivity of solvent-doped PEDOT:PSS films.The conductivity of solven-doped PEDOT:PSS films was improved by alcohol/acid post-treatment,and the mechanism of improving the conductivity of different PEDOT:PSS films was discussed.The results show that when formula C2(PEDOT:PSS+5%DMSO+23%IPA)is applied on inkjet printing paper with high smoothness and low air permeability,the solution has the best film-forming property and the best conductivity.When wet PEDOT:PSS film was post-treatment by glycerol,the sheet resistance of the film is the lowest,which is 140 Ω/□.The conductivity of the PEDOT:PSS film is related to its crystal form,molecular structure and PSS content in the film.The higher the degree of crystallization of PEDOT:PSS film,the transition of the PEDOT main chain structure(from benzene structure to quinone structure),the less the content of SO3 group in PEDOT:PSS film(the less PSS content),the higher the conductivity of the PEDOT:PSS film.Secondly,we consider that paper is a substrate that enables PEDOT:PSS solution printing into a film,but the porosity and unevenness of the paper will affect the absorption and film formation of the solution.Therefore,in this paper,four layers of filling layer,smoothing layer,barrier layer and top coating are constructed on the paper.Then three printing methods of rod-coating,screen printing and gravure printing were used to form a film of PEDOT:PSS solution on the constructed coated paper.Different printing methods use different PEDOT:PSS solution formulas.The doped solvents(DMSO,IPA,PVA,Me,EG)were used to optimize the formulation of the PEDOT:PSS solution.The uniformity of films formed by different formulations of PEDOT:PSS solution was observed by ultra depth of field microscope.The results show that the functional layer formula of the constructed coated paper is:formula I4(filler layer),formula Ⅱ4(smooth layer),formula Ⅲ11(barrier layer),formula IV3(top coating).The best PEDOT:PSS solution formulations for bar coating,screen printing and gravure printing are PEDOT:PSS+5%DMSO+23%IPA,PEDOT:PSS:Me(1:1)+7wt%PVA,PEDOT:PSS:Me=93:7.Finally,we considered that the PEDOT:PSS film has conductivity and electrochromic properties,and electrochromic devices can be applied in the field of printing anti-counterfeiting.This paper explored the performance of paper-based electrochromic devices based on PEDOT:PSS.The starting voltage,color changing effect,ultraviolet absorption and bending resistance of six electrochromic devices prepared by three printing methods on two kinds of paper were analyzed.The results show that the electrochromic device prepared on the constructed coated paper by gravure printing has the best physical parameters.The starting voltage is 0.15 V;The chromatic aberration is 26.53;The response time is 1s;The ultraviolet absorption difference is 0.31;The change in chromatic aberration is about 1 after 1000 bending cycles.