The Construction And Photoelectric Properties Of WO₃ Based Multifunctional Electrochromic Films/Devices

Electrochromic（EC）materials can switch their optical properties such as transmittance,reflectivity and absorptivity stably and reversibly under the external electric field,which have been exhibited great prospect in anti-glare rearview mirrors,smart energy-saving windows,electrochromic glasses,military camouflage equipment,electrochromic display,and so on.However,the reports of EC matertils till now are focused on the color change of the materials before/after EC behavior in the bright field,and other propertits change of materials like the conductivity during the electrochromic process and their applications in the dark field have been less researched.In this work,we focus on the difference of electrical conductivity of materials during the electrochromic process and their applications in the bright/dark field,and expolore WO₃-based electrochromic materials in the following two aspects:（1）the conductivity change rule of WO₃ during the electrochromic process was studied,and WO₃/PANI based electrochromic switch was further constructed based on the above change rule for fixed point display application in the bright field;（2）WO₃ and lanthanide metal-organic frameworks（Ln-MOFs）films/devices were developed for the encryption of binary（color change/bright field）and Morse code（fluorescence/dark field）,and the anti-counterfeiting application of electrochromic fluorescent device in the bright/dark field was explored,which provided a new idea for anti-counterfeiting application.The specific work of this thesis is as follows:Firstly,the laminated tungsten trioxide/polyaniline（WO₃/PANI）composite film was prepared on the fluorine-doped tin oxide（FTO）conductive glass by the stepwise electrodeposition method.The in-situ Raman,electrochemical impedance and violet-visible absorption spectra proved that the conductivity of WO₃layer in the colored state（blue）is obviously better than that in the blached state（transparent）.The charge transfer process between polyaniline layer and FTO layer is adjusted by the electrical conductivity difference,which can controll the electrochromic properties of polyaniline layer,so the visual WO₃/PANI electrochromic switch was constructed.When the charge transfer channel is open,the color of the composite film is dark blue,and when the charge transfer path is closed,the color of the composite film is pale blue.To exhibit the application scenario of the electrochromic switch,a panda patterned film was constructed based on the WO₃/PANI electrochromic switch for fixed point（special point）display.Secondly,to expand the application of electrochromism in the bright and dark fields,heterogeneous films of tungsten trioxide and lanthonide metal-organic frameworks（Ln-MOFs）materials were constructed.The electrochromic properties of WO₃ were employed in binary encryption.The color state（blue）presented1 in binary encryption,and the color state（transparent）presented 0 in binary encryption.Benifiting from the easily tunable fluorescence features of Ln-MOFs,the Ln-MOFs with red,green and yellow emission were obtained by adjusting the ratio of terbium（Tb）to europium（Eu）lanthanide ions and sprayed on the side of WO₃ film.Here,the green fluorescence and the red fluorescence were chosen to represent"short"（·）and"long"（—）of Morse code respectively for Morse code encryption.Based on the predesigned scheme,the WO₃/Ln-MOFs bright/dark field electrochromic fluorescent device was constructed,in which WO₃ segment outputted the preloaded information"EC",and Ln-MOFs segment outputted the preloaded information"HENU",realizing the anti-counterfeiting application in the bright/dark field.Compared with the single chromic anti-counterfeiting device,electrochromic fluorescent device can transmit more optical information in bright/dark fields,which has more application value in the anti-counterfeiting field.