Achieving Multimodal and Multicolor Luminescence in LaAlO3:Pr3+, Gd3+ via Trap Engineering and Energy Transfer

A single LaAlO₃:Pr^{3 +}, Gd^{3 +} phosphor exhibits penta-modal luminescence (down-conversion luminescence, up-conversion luminescence, persistent luminescence, optically stimulated luminescence, and thermally stimulated luminescence) across ultraviolet–visible–near-infrared regions, enabled by distinct traps (0.69–1.15 eV) and defect engineering, with applications in data storage, anti-counterfeiting, and phototherapy.

Achieving multimodal luminescence within a single phosphor is vital for multifunctional applications but remains challenging due to complex color tuning and trap engineering. In this study, we report Pr³⁺ and Gd³⁺ co-doped LaAlO₃ (LAO:PG) phosphors, designed through careful modulation of multilevel traps and Pr³⁺ → Gd³⁺ energy transfer dynamics. These materials exhibit diverse luminescence modes, including down-conversion luminescence (DCL), up-conversion luminescence (UCL), persistent luminescence (PersL), optically stimulated luminescence (OSL), and thermally stimulated luminescence (TSL) across a wide spectral range. Unlike previously studied Pr³⁺-doped LAO, the co-doped LAO:PG shows DCL in both UV-visible and NIR regions and displays ultraviolet-C UCL under visible excitation. Notably, we observe, for the first time, PersL lasting several minutes in these phosphors—an improvement over the non-PersL behavior of Pr³⁺ -only doped LAO. Additionally, the LAO:PG phosphors exhibit strong OSL response. TSL analysis reveals five distinct trap levels linked to these properties. Density functional theory calculations further correlate intrinsic defects to these traps, supporting a proposed mechanism for the observed multimodal luminescence. These findings highlight LAO:PG as a promising platform for developing advanced phosphors with integrated luminescence modes, paving the way for future applications in data storage, phototherapy, and anti-counterfeiting technologies.

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