Modulating Tetra-Modal Luminescence of LaAlO3:Sm3+ Storage Phosphors Through Intrinsic Defect Engineering and Co-Doping

Abstract

Long-lasting persistent phosphors with efficient multimodal luminescence properties serve not only as effective storage phosphors but also as essential components for developing reliable anticounterfeiting materials. However, achieving simultaneous multimodal luminescence in storage phosphors poses a significant challenge, as it necessitates the coexistence of multiple luminescence mechanisms within the same matrix along with the creation of effective traps at various energy levels for charge carrier storage. This study presents the synthesis of LaAlO₃ phosphors doped with varying mol % of Sm³⁺ using a coprecipitation method followed by a molten salt reaction. The objective is to investigate their multimodal luminescence properties and potential applications in optical storage and anticounterfeiting. These phosphors exhibit persistent luminescence (PersL) lasting for hours and controllable by doping levels along with efficient optically stimulated luminescence (OSL) when being excited by a 980 nm laser after UV preirradiation. Thermo-stimulated luminescence (TSL) reveals multiple deep traps with enhanced OSL. Additionally, the LAO:0.5S phosphor shows PersL upon X-ray irradiation, suggesting potential for imaging applications. Gd³⁺ incorporation optimized PersL and OSL performance while DFT calculations elucidated trapping mechanisms. These findings of tetra-modal luminescence comprising downconversion luminescence (PL & RL), PersL, OSL, and TSL highlight the multifunctional potential of these LaAlO₃-based phosphors for advanced optical applications.