Improvement in Photochromic Property of Nickel Oxide-Based Photochromic Composite Films by Cobalt Addition

Nickel oxide (NiO)-based composite films with various Cobalt/Nickel (Co/Ni) ratios were fabricated, and the photochromic properties of the resulting films were evaluated. The NiO particle sizes in the composite films with Co/Ni ratios of 0~0.02 were 40~70 nm. Increase in the Co addition ratio to the composite films caused a decrease in the initial transmittance of the films, and the films with Co/Ni ratio of 0.005 and 0.01 showed a larger transmittance modulation. Co addition caused an increase in the bleaching and coloring rates, which were the largest in the film with Co/Ni ratio of 0.005.