Ionic liquid- and surfactant-controlled crystallization of WO3 films

Abstract

WO₃ films were obtained via evaporation-induced self-assembly (EISA) using ionic surfactants such as long-chain ionic liquids 1-hexadecyl-3-methyl imidazolium chloride and bromide (C₁₆mimCl and C₁₆mimBr, respectively) and cetyltrimethylammonium chloride and bromide (CTAC and CTAB, respectively) as additives. Owing to the presence of the ionic surfactants, WO₃ films crystallize in a preferred orientation along the a-axis on different substrates, as evidenced by X-ray diffraction. WO₃ films with this orientation show improved electrochromic properties when compared to films with a lower degree of crystallographic orientation, prepared in an analogue fashion.