Electrochromism And The Electrochromic Devices Based On Small Organic Molecules

Electrochromism(EC)refers to the phenomenon that the optical behaviors of specific materials could be able to change reversibly under external bias.Generally,electrochromism is caused by the electro-redox process of electroactive materials.With the doping and re-doping in electrolyte,materials thus show great change in reflection,transmittance or absorption.The optical behaviors of above electro-chromic materials are controllable and attract the extensive attention of researchers.Up to now,above materials are widely employed in display technology,such as glare-proof mirrors,smart windows,glasses and electronic displays.Among the numerous electrochromic materials,organic molecules could be facilely processed and reveal high optical contrast with rich colors.Viologens and phthalates,however,are praiseworthy to be further investigated.This work concentrates on the optimization of viologens and phthalates,and achieves high-performance optical derivatives.Meanwhile,the electrochromic mechanism of these derivatives was investigated in detail as well.In the first and second parts of our work,we introduced two kinds of aromatic derivatives into the bi-pyridines of viologens.One is a series of substituted benzene,and another is large conjugated aromatic rings.The obtained "extended" viologen derivatives achieve abundant EC behaviors,and the various "linkers" have significant effects on the electrochemical and optical properties of above derivatives.These"extended" viologen derivatives exhibit vivid colors,ultra-high optical contrast over.60%,rapid EC response within few seconds and thousands of cycles' switching stability.Additionally,we explored the EC mechanism of above viologen derivatives via the electrochemical investigation,and found that the colored derivatives could be achieved by a one-step two-electrons reduction process,which is quite different from the traditional viologens(such as MV2+).Surprisingly,several viologen derivatives with electro-rich "linkers" have electrofluorochromic nature and the fluorescent mechanism was also researched.Other data of above derivatives and corresponding devices is discussed in later chapters.In another part,we introduced various substituents on the frmework of terphenyl phthalates and obtained four electro-active derivatives.The different band gap of the derivatives results in abundant optical behaviors.Four phthalate derivatives reveal navy,purple,pink and atrovirens in their colored state,and high optical contrast over 50%.We also researched the EC mechanism of these derivatives via the combination of in-situ electron paramagnetic resonance and electrochemistry study.Furthermore,owing to the electron-rich nature of methoxyl,its corresponding phthalate Oxy-p has a strongly blue emission,which proves the derivative qualified for the fluorescent displays.