Synergistic Integration of NB‐UVB Persistent Luminescence and Concentration‐Dependent Photochromism in a Phosphate Phosphor for Multifunctional Applications

Abstract Multifunctional phosphors combining persistent luminescent and photochromic properties have garnered increasing attention, given their capability of absorbing the photon energy and trapping the light‐generated charge carriers by defects. To date, extensive efforts have been devoted to achieving reversible photochromism in visible/infrared afterglow materials. However, research on integrating ultraviolet (UV) persistent luminescence and photochromic behavior into a single material is relatively lacking. Herein, multimode luminescence in a Gd ³⁺ single‐doped Sr ₃ (PO ₄ ) ₂ phosphor is demonstrated, featuring narrowband ultraviolet‐B (NB‐UVB) photoluminescence, NB‐UVB afterglow, and multicolor photochromism. The temperature‐dependent NB‐UVB photoluminescence of the Sr ₃ (PO ₄ ) ₂ :Gd ³⁺ phosphor reveals its potential as a ratiometric optical thermometer with high relative sensitivity (2.5% K ⁻¹ at 110 K). Meanwhile, this phosphor exhibits robust NB‐UVB persistent luminescence lasting >24 h upon X‐ray irradiation. Besides, the material also displays exceptional concentration‐dependent multicolor photochromism (white‐to‐blue and white‐to‐brown) under bright‐field conditions only in response to X‐ray irradiation, coupled with excellent bleaching and recovery capability under thermal treatment or 254 nm UV light stimulation. The synergistic integration of NB‐UVB persistent luminescence and concentration‐dependent multicolor photochromism positions this phosphor as a promising candidate for versatile applications, including covert optical tagging, optical information storage, and advanced anti‐counterfeiting.