Fabrication of Large Area Crack-Free 2D and 3D WO3 Inverse Opal Films by "Dynamic Hard Template Infiltration Strategy"

Large-area crack-free 2D and 3D WO3 inverse opal (IO) films, using a wide range of sizes of sacrificial PS spheres as colloidal crystal template, were fabricated by "dynamic hard template infiltration strategy". First a dynamic PS opal film was formed floating on the surface of water followed by infiltration of a preformed WO3 sol underneath the PS opal film. The resultant PS/WO3 opal composite film was then deposited on various types of substrates (rigid and flexible) and 2D WO3 IO films were obtained following the removal of the PS template by chemical method. Based on this strategy, multiple layer WO3 IOs were fabricated through a layer by layer route. The WO3 IO films deposited on indium tin oxide coated conductive (ITO) substrates were used as active electrode in the fabrication of electrochromic devices, demonstrating their advanced properties for electrochromic application.