Preparation Of Au NP/PB Thin Films And Electrochromic Properties Research

Due to the excessive extraction and consumption of energy,energy depletion and environmental issues have arisen.Electrochromic materials can be applied to construction and other fields on account of reversible stability and adjustable optical properties under a low voltage to achieve the purpose of energy saving.Prussian blue(PB)is often used in electrochromic materials because of its open frame structure.However,its electronic conductivity is poor by reason of wide band gap.Traditional methods such as compounding with highly conductive materials or doping are employed for improving the conductivity of the material itself.Nevertheless,the high contact resistance between the film and the substrate is ignored,hence how to reduce the contact resistance has become a research focus.In addition,a challenge of breaking and falling off exists in PB film.In this dissertation,we carried out research into the electrochromic performance of PB by modifying Au nanoparticles(Au NP)to reduce the contact resistance and improve the interface stability for satisfying the needs of response speed and cycle performance.In order to obtain the Au NP with preeminent monodispersity and the adjustment of the particle size of the nanoparticles,we synthesized the Au NP on ITO substrate by two steps electrodeposition.The particle size,monodispersity,and spectral characteristics of the Au NP were characterized to study the effects of nucleation voltage,growth voltage,and growth time on the morphology of Au NP.the growth conditions most conducive to the monodispersity of Au NP can be achieved by means of regulating the growth voltage and growth time.on the basis of this,a series of gold nanoparticles with excellent monodispersity and controllable particle size can be acquired through a single adjustment of the nucleation voltage.The electrochromic performance of the Au NP/PB film was studied.A constant voltage method was used to deposit a PB on the ITO substrate modified with Au NP,and a composite film with the largest optical modulation range was obtained by controlling the deposition time.Composite film has a fast response time : tb=1.88s?tc=1.19 s because the lower contact resistance of the composite film accelerates the interface charge transfer.Meanwhile the cycle performance was improved from maintaining 36.5% of the initial optical modulation to 98.9% after 1500 cycles since the problems of film surface cracks and volume expansion were also effectively figured out.For exploring the mechanism of interfacially modified Au NP to improve the electrochromic performance of PB,we conducted EIS and XPS tests and comparisons on a pure PB film and the composite film.On the one hand,the Au NP with high specific surface area increase the electrical contact area between PB and ITO,and an ohmic contact is constructed through charge exchange between Au NP and waterdoped PB,which reduces the contact resistance by about 90%.On the other hand,Au NP with homogeneous size promote the homogeneous growth of PB at the interface,reduce the compressive stress and increase the binding force through the electronic coupling to improve the cycle performance.