Efficient electrochromic properties of high-density and large-area arrays of one-dimensional NiO nanorods

We report on the electrochromic properties of transparent one-dimensional nickel oxide (NiO) nanorods grown in a high-density and large-area array. The NiO nanorod array was synthesized on a conducting indium tin oxide thin film via hot-filament metal-oxide vapor deposition (HFMOVD). The array contained ∼100 nanorods per square micrometer, which were ∼500 nm long and ∼100 nm wide. XRD analysis revealed the 1D NiO nanorods to be in cubic crystalline form within space group F m 3 ¯ m . The outstanding electrochromic properties, including the stable and reversible coloration–bleaching cycles, and large diffusion coefficient (∼6.33×10−8 cm2/s), as well as good coloration efficiency (43.3 cm2/C), great optical transmittance difference (60%), high optical density (1.06), and very fast coloration and bleaching times (1.55 and 1.22 s) at a wavelength of 630 nm, make the NiO nanorods excellent materials for use in smart windows.