Novel Non‐Rare‐Earth‐Activated Phosphor With Multicolor Emissions Used for Dynamic Fluorescent Anti‐Counterfeiting

ABSTRACT With the urgent demand for dynamic anti‐counterfeiting technology, developing multicolor phosphors, being sensitive to excitation wavelength, has become a novel research hotspot, especially for non‐rare‐earth‐activated multicolor phosphors. In this work, the multi‐site‐induced multicolor emissions have been successfully achieved in Bi 3+ ‐doped NaCa 2 GeO 4 F. By slightly adjusting the excitation wavelength from 320 to 360 nm, the emission color of NaCa 2 GeO 4 F: Bi 3+ can change from blue to cyan along with an obvious redshift of the emission band varying from 420 to 490 nm. The results indicate that NaCa 2 GeO 4 F: Bi 3+ presents a significant excitation‐wavelength‐dependent multicolor emission. Combining the experimental analyses and theoretical calculations, the intriguing photoluminescence characteristics of Bi 3+ ions in NaCa 2 GeO 4 F have been considered to be associated with multiple crystallographic sites, and the tight crystal structure of NaCa 2 GeO 4 F makes Bi 3+ ions exhibit excellent hydrolysis resistance. Benefiting from the unique characteristics of Bi 3+ ‐activated NaCa 2 GeO 4 F, its actual application in white‐light‐emitting diodes has been demonstrated, and moreover, a promising fluorescent anti‐counterfeiting coating emitting multicolor lights has also been successfully synthesized to realize a dynamic anti‐counterfeiting label. The results pave an available strategy for the development of Bi 3+ ‐activated phosphors with multicolor emissions used for dynamic fluorescent anti‐counterfeiting technology.