Multicolor chromism in Co-doped YNbO4 via synergistic coupling of photochromic and chemical coloration

Photochromic materials have attracted considerable attention owing to their promising applications in smart displays and optical information storage. However, most photochromic materials still face challenges, such as limited coloration and low photochromic efficiency, which restrict their potential applications in multicolor displays and high-quality optical storage. In this study, Co ions were selected as a coloring agent, and introduced into YNbO 4 matrix, showing high efficient photochromism and chemical coloration properties. Under 265 nm irradiation, the photochromic efficiency increases from 45.6% (x = 0) to 71.5% (x = 0.003), while the luminescence modulation ratio rises from 33.6% to 72.2%, thereby substantially improving optical storage capability. Most importantly, Co doping expands the surface color range from pale yellow (x = 0) to green (x = 0.001) or blue (x ≥ 0.003), and the photochromic coloration changes from brown (x = 0) to dark grey (x ≥ 0.001) after 265 nm irradiation, realizing multicolor chromism. Such multicolor features rely on synergistic coupling of photochromic and chemical coloration. These results highlight the great potential of the YNbO 4 :xCo system for multicolor display and optical storage, and provide valuable insights for future design of multicolor photochromic materials.