Light‐ and Heat‐Responsive High Contrast Multicolor Photochromic Materials

Abstract Multicolor photochromic materials exhibit potential applications in high‐level information encryption, temperature monitoring, and chemical detection. However, critical challenges remain in simultaneously achieving both high color contrast and multicolor photochromism in a single inorganic material. Herein, BaMgSiO 4 :Co co‐doped with Fe, Cr, or Mn, displaying enhanced color contrast and rich colorations under 254 nm light irradiation are reported. Notably, BaMgSiO 4 :Co, Fe exhibits a visible color change from light blue to light purple under 254 nm light irradiation, with a maximum color contrast of 75.2%. In addition, under both clear and overcast skies, BaMgSiO 4 :Co, Fe exhibits environmental UV response, with its color contrast dynamically varying with the corresponding UV intensity. Moreover, temperature‐dependent multicolor changes (light purple, gray, and blue) are achieved in BaMgSiO 4 :Co, Fe, due to the stepwise release of electrons captured by defect energy levels with multiple depths upon heating. These findings promote the design of multi‐stimuli‐responsive multicolor photochromic materials, thus broadening the applications of photochromic materials.