Preparation of a porous NiO array-patterned film and its enhanced electrochromic performance

In this paper, a novel photochemical etching technology, a photosensitive sol–gel method, was employed to prepare a porous NiO electrochromic patterned film. The sol was first prepared using nickel(II) acetate as the raw material, anhydrous methanol as the solvent and acetylacetone as the photosensitizer. Then, the chemically-modified NiO gel film was prepared on a glass substrate coated with ITO film. The obtained NiO gel film has a strong photosensitivity to ultraviolet light with a wavelength of 305 nm. Therefore, after UV exposure, rinsing with solvent and heat treatment, the NiO gel film covered with a porous array mask can be converted into a porous NiO array-patterned film. Compared to the compact NiO film, the porous NiO patterned film has a wider optical modulation range (51%), higher coloration efficiency (40 cm2 C−1), longer service life (with a peak current density reduction of <10% after 3000 cycles) and higher switching speed (coloring time 7 s, bleaching time 5 s).