The Study Of Self-healing Electrochromic Materials And Device

Electrochromism is the reversible color changes in the transmittance and/or reflectance of thin-film materials by applying different voltages.Self-healing Electrochromic materials are a kind of advanced intelligent bionic materials with electrochromic and self-healing properties.No question that the generation of cracks from aging or reiterative bending was inveitable when the electrochromic films used for a period of time,and the performance of the electrochromic devices?ECD?would be weakned,even scraped.So repairing cracks timely would be vital for prolonging the service life of ECD.However,traditional electrochromic materials which are the crucial component of the ECD are not intrinsically healable.Here useful attempts were conducted to synthesize Self-healing Electrochromic polymer TPFMA and PPFMA through the Diels-Alder?DA?reactions.These materials can repair the cracks only by means of heat treatment without catalyst or other special treatment.It was the first time to make the electrochromic films curable by themselves when be damaged.And the more details are as follows:1. The triphenylamine?TPA?diamine derivatives reacted with furfural to form a compound?TPF?bearing two furan groups,and then TPF polymerized with N,N'-?4,4'-Methylenediphenylene?dimaleimide?MA?through the Diels-Alder reaction to obtain the linear polymer TPFMA.The results show that the TPFMA film could change its color from yellow to red reversibly.The response times of TPFMA film were10 s for coloring process and 12 s for bleaching.There were a pair of strong endothermic/exothermic peaks related to the retro-DA and DA reaction respectively in the DSC curve.A crack?3.24 mm*0.04 mm?on the yellow film surface was disappeared completely in 206 s when heated at 130°C,the crack?4.02 mm*0.04 mm?on red film was also rehealed within 219 s.The healing efficiency of polymer TPFMA reached 72%.2.To improve the efficiency of repair and the kinds of colors,useful attempts were conducted to synthesize network polymer PPFMA through the Diels-Alder reactions of MA and the triphyelamine derivative?PPF?functionalized by Furfuryl glycidyl ether.The polymer was coated on the ITO glass to obtain a film which can change its color from yellow to green to blue reversibly,coloring and bleaching times were 12.8 s and13.5 s respectively.Besides,the film showed the outstanding stability for long-term EC operation with high optical contrast of 42.7%and good CE of 73 cm² C^-1 at 1000 nm.Cracks on the bleached films and the colored films could be self-repaired after heating at 130°C within 221 s.After healing,the films still remained electrochromic.The healing efficiency of polymer PPFMA reached 74%.All the results proved that the polymer film showed excellent electrochromic and self-healing performances such as large optical contrast,high coloration efficiency,long-term stability and fast healing process.And apparently,the Self-healing Electrochromic PPFMA film can be considered as a promising film to extend the service life of ECD.3.A hard Self-healing Electrochromic device was produced through stacked structure,in which PPFMA film was used as the electrochromic layer and ITO-coated glass substrate was the transparent conducting electrode.The device had longer service life and ideal color changing?yellow,green,blue?.The response times of the bleached states and the colored state were 15 s and 13 s,respectively.