Lattice engineering mediated fast decay in Li2HfF6:Mn4+ with dual-excitation-band responsive differential emission for fingerprinting, anti-counterfeiting, and optical signal transmission

Abstract

Mn4+ -doped fluoride phosphors exhibit excellent red monochromaticity and high luminous efficiency, giving them broad application prospects in lighting and backlight display. However, their practical development is limited by prolonged luminescence decay times, and there remains a lack of research on the regulation of their excitation response characteristics, which severely restricts their utility in variable-input optical information systems. Here, we report a Mn4+-doped A2BF6-type fluoride red phosphor with an average lifetime of 2.8 ms synthesized based on lattice engineering strategy, where Li is employed as the A-site ion and Hf as the B-site cation. The design-synthesized Li2HfF6:Mn4+ exhibits two well-resolved excitation bands at 376 and 487 nm that produce the same narrow-band red emission at 633 nm with distinctly different excitation efficiencies, enabling excitation-selective regulation within a single emission channel. By coupling wavelength addressable excitation with differentiated temporal responses, a programmable optical encoding strategy is achieved for excitation-selective fingerprint identification. More importantly, combining the short-decay emission of Li2HfF6:Mn4+ with the long-decay emission of K2SiF6:Mn4+ (τ = 9.07 ms), a monochromatic multiplexing anti-counterfeiting system in the millisecond regime is realized, allowing rapid and highly secure machine-readable decoding. Furthermore, by integrating the as-synthesized Li2HfF6:Mn4+ phosphor with a 460 nm chip, the as-fabricated phosphor-converted LED enables efficient optical signal transmission over a distance of 10 m. In comparison with the LED assembled using commercial K2SiF6:Mn4+ phosphor, the present system exhibits a wider modulation bandwidth (12.9 MHz) and faster data transmission rate (20 Kbps).