Study On Nanostructure Regulation Of Prussian Blue Electrochromic Materials And Properties Of Multifunctional Devices

Electrochromic devices（ECDs）have been widely used in energy-saving smart windows,anti-glare mirrors and high-contrast displays.It has become an extremely urgent task to further improve electrochromic performance,enrich color change and expand application field.Prussian blue（PB）electrochromic materials are taken as research object in this paper.Ti O₂ nanorod arrays（TNRA）were constructed on Sn O₂:F（FTO）films.And then graphene（G）was combined to prepare TNRA@G/PB core-shell nanostructured composite films and ECDs;Three-color Prussian green（PG）electrochromic films and ECDs were synthesized by one-step hydrothermal method,which have good electrochromic properties and can be stably changed between green,blue and colorless;Surface-modified PB nanoparticles（PB NPs）were deposited on ITO/PET substrates by spin coating and fabricated as flexible PB ECDs;Multicolor composite flexible electrochromic films were obtained by layer-by-layer spin coating of two different nanoparticles by doping PB NPs with Ni and Co elements,respectively.The flexible PB analog（PBA）electrochromic device with high visual contrast was constructed.The structure,morphology,electrochemical properties and electrochromic properties of the films and nanoparticles were characterized by XRD,Raman spectroscopy,SEM,TEM,UV-Vis spectrophotometer and electrochemical workstation;The existence state of iron and evolution of the PB growth layer were explored by the X-ray photoelectron spectroscopy（XPS）deep etching analysis.The interfacial behavior of the thin films was studied in depth,and it was determined that there were chemical interactions between the film layers.Research indicates:Compared with PB film,TNRA@G/PB core-shell nanostructures achieve a higher optical modulation range（56.1%）,a shorter switching time（t_c/t_b=1.0/2.8 s）and a more significant tinting efficiency（129.1 cm²/C at a wavelength of 700 nm）.The redox system in the films was obviously controlled by diffusion,and the diffusion rate of K⁺determined the reaction rate.The porous core-shell nanostructure promotes the direct contact between the electrolyte and underlying PB,which increases the reaction sites and reduces the diffusion distance of ions.G acts as a bridge between the FTO films and PB layer and provides a fast transport channel for electron transport.A large number of electrons are transported into the active layer to participate in redox reactions.The PG ECDs achieved good electrochromic performance under the condition of realizing various color changes.The optical modulation range and response speed are 55.2%and t_c/t_b=2.1/7.4 s,respectively.The different color states depend on the ratio of Fe³⁺/Fe²⁺in the PG film structure.The PG films were demonstrated that have smaller resistance to ion diffusion and charge transfer by the electrochemical impedance studies.Soluble PB NPs were successfully prepared by surface modification and deposited on ITO/PET substrates.A new breakthrough of PB group electrochromic materials in flexible devices has been achieved.It has a high optical modulation range（48.6%）,a fast response speed（t_c/t_b=5.9/4 s）and a large coloring efficiency（90.4 cm²/C）at a specific wavelength.The study of the change of charge amount shows that a part of Li⁺embedded in the film is blocked in the film matrix,which improves the memory effect of the devices.Compared with the dense PB films prepared by hydrothermal or electrodeposition methods,the PB nanoparticle films achieved a highly reversible transition of PB between the yellow state and other color states.The visual contrast of PBA ECDs are improved by Ni-PBA and Co-PBA flexible electrochromic films prepared by doping Ni and Co elements in PBA.A higher light modulation range（55%/16%）and faster response speed（t_c/t_b=6.1/4.3 s,t_c/t_b=5/4.1 s）have been achieved;A flexible electrochromic film and device with high visual contrast and stable change among colorless,blue,green,and yellow states was obtained by alternately spin-coating PB and Ni-PBA nanoparticles layer by layer.