Preparation And Properties Of The Viologen-based All-solide-state Electrochromic Device

Electrochromism is a redox reations process involved the alteration of absorption by electrochemical generation.It is a property shared by some electroactive species（also called electrochromic materials）.Electrochromic Devices made by EC devote itself to green photovoltaic information display application.EC technology attracts so many scientists’ interests because of its unique characters,such as high optical contrast,low driving voltage,fast response time,good controllability and easy-to-make.In this paper,we prepared a new kind of EC gel and a new type of all-solid-state electrochromic device.EC gel contains ethyl viologens(EtV²⁺),N,N,N’,N’-Tetramethyl-p-phenylenediamine（TMPD）,polyvinyl butyral（PVB）and a kind of high boiling solvent（2-（2-Butoxyethoxy）ethanol）.We explored the best constituent of EC gel and the excellent properties of the ECDs.The results are as follows.（1）The best constituents’ mass rate as-prepared EC gel was confirmed to be 4:0.5:38:57(EtV²⁺:TMPD:PVB:solvent).The absorption spectra of EC gel presented peaks at570 nm and 615 nm with the variation of applied cell voltage（0-0.7V）.Cyclic voltammograms test demonstrated the good reversibility of the EtV²⁺-PVB-based EC gel.The addition of small amounts of TMPD acted as complementary redox species enhanced the electrochemical process of the EC gel,so that lower applied cell voltage can be used on ECDs.（2）The fabrication of the ECDs was very easy.As-prepared EC gel and two ITO glasses were the mainly part of ECD which like sandwiches structure.And the performance of the all-solid-state ECD were tested.Et V²⁺-PVB-based ECD has reversible color change from colorless to dark blue.Large transmittance changes（△T）over 60% at both 570 and 615 nm were achieved when the EtV²⁺-PVB-based ECD was switched from0 V to a low potential bias of 0.7 V.There was no obviously decline in the ECD after 300 continuous cycles at bleaching/coloring voltages of 0/0.7 V with an interval of 30 s for both bleaching and coloring processes.Large transmittance changes（△T）over 60% at615 nm were achieved when the EtV²⁺-PVB-based ECD was switched from 0 V to 0.6 V.There was no obviously decline in the ECD after 1000 continuous cycles at bleaching/coloring voltages of 0/0.6 V with an interval of 30 s for both bleaching and coloring processes.In summary,EtV²⁺-PVB-based electrochromic device was prepared in order to develop novel high-performance,easy-to-make inexpensive ECDs.Research on EtV²⁺-PVB-based ECD in detail is for the first time.The good results obtained in terms of transmittance,response time,conductivity and cyclability suggest that EtV²⁺-PVB-based ECD could have a promising potential for the inexpensive smart window and other ECD fabrication.