Preparation Of WO₃/PEDOT?PSS Composites For Electrochromic Applications

Energy saving and cons?mption reduction are crucial for the sustainable development of h?man society.Electrochromic technology is designed for a new way of energy conservation.The electrochromic smart window can dynamically adjust the amount of incident light through changing its own color under very low voltage,which makes room temperature more controllable.In order to accelerate the process of its industrial application,much more research efforts must be made to enhance the electrochromic properties of the electrochromic materials.Both of WO3 and Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate(PEDOT:PSS)are cathodic coloring materials with excellent optical and electrical properties.It is worthwhile to combine those two kinds of material to improve the electrochromic performance.In this paper,the WO3 nanorods was synthesized by the kettle method and the high-gravity method,respectively.The WO3/PEDOT:PSS inorganic/organic nanocomposite was prepared by the in-situ polymerization method,and the electrochromic film was prepared by a simple coating method.The influence of the preparation process conditions on the morphology of WO3,WO3/PEDOT:PSS composites and the electrochromic properties of electrochromic films were investigated.The main research content and conclusions are as follows.The H2WO4 precursor with small and uniform size were prepared by high-gravity technology,and WO3 nanorods were prepared by means of hydrothermal method afterwards.The influence of different conditions on the morphology and structure of WO3 nanorods was studied.The suitable process conditions are as follows:The mass ratio of Na2SO4 and the Na2Wo4.2H2O is 2,the pH is 2,the rotation speed of rotating packed reactor(RPB)is 1500 rpm,the reaction time of the precursor is 10 min and the time of hydrothermal is 24 h.When compared to the kettle method,the high-gravity method can reduce the reaction time of the precursor,and the prepared WO3 has more uniform morphology with average diameter of 80 nm and average length of 2 ?m.The WO3/PEDOT:PSS composites was prepared by in-situ polymerization.The first step is the surface modification of WO3 nanorods,and the WO3/PEDOT:PSS nano-composites were synthesized on the surface of WO3 nanorods afterwards.The main conclusions were as follows:The mass ratio of KH540 and WO3 is 1:4,the most suitable temperature for modification is 70?.The prepared composite material has a core-shell structure,and the thickness of PEDOT:PSS as the shell is about 20 nm.The WO3/PEDOT:PSS composite material prepared by in-situ polymerization was used to prepare the electrochromic film by a simple coating method,and it was compared with the WO3-PEDOT:PSS film prepared by mixing the WO3 and PEDOT:PSS that both were prepared separately.The optical contrast of WO3/PEDOT:PSS films is 49.8%,tc is 10.3 s,tb is 5.2 s,and the coloring efficiency is 217 cm2 C'1.Compared with the WO3-PEDOT:PSS,the WO3/PEDOT:PSS film exhibits better electrochromic performance with a larger light modulation and a higher coloring efficiency.