Defect-Assisted Dual-Channel Optical Storage Material with Photochromism and Concealed Persistent Luminescence

Abstract

Optical information storage technology offers several advantages, including cost-effectiveness, multidimensional storage, and rewritable capability. Consequently, it has become increasingly popular for optical storage media. Herein, a novel optical information storage material Na₂CaGe₂O₆:Bi³⁺ (NCGO:Bi³⁺) is developed using a non-equivalent substitution strategy, which exhibits photochromic (PC) and ultraviolet persistent luminescence (UV PersL) properties. NCGO:Bi³⁺ demonstrates excellent white-to-brown PC performance under 254 nm light irradiation. The brown phosphor can be effectively bleached using 425 nm light or thermal stimulation, demonstrating excellent reversibility over multiple cycles. Additionally, the phosphor displays UV PersL characteristics. The representative sample NCGO:0.001Bi³⁺ with a duration time exceeding 10 h after 254 nm light excitation, peaking at 358 nm. Simultaneously, due to the electrons captured by deep traps can be released via low-energy light excitation, the sample also exhibits photostimulated PersL characteristics. Specifically, oxygen vacancies (V_O) are identified the primarily responsible for the observed PC and PersL phenomena by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analyses. Overall, this work indicates that the combination of 254 nm light-induced PC and PersL in a single material has potential for designing advanced luminescent materials for the application of optical information storage.