Battery‐Free UV‐Dose Detector via Defect‐Engineered Ca 2 SnO 4 :RE (RE = Sm 3+ , Pr 3+ ) Oxide Phosphors

ABSTRACT We report the defect‐related luminescence properties and non‐powered UV detection capabilities of Sm 3+ and Pr 3+ ‐doped Ca 2 SnO 4 (CSO:RE, RE = Sm and Pr) phosphors. Under UV excitation, CSO:RE exhibits distinct orange and deep‐red emissions due to characteristic 4f–4 f transitions of RE 3+ ions. Comprehensive long‐persistent luminescence (LPL), thermoluminescence (TL), and optically stimulated luminescence (OSL) measurements confirm the presence of thermally and optically responsive trap states. Notably, our samples demonstrated highly stable OSL signals even after 504 h of storage in a dark environment, evidencing excellent information storage retention. Finally, leveraging these properties, we demonstrate battery‐free UV‐dose detectors that operate under ambient sunlight and enable optical readout. Our approach requires zero operational energy, avoids battery‐ and wiring e‐waste, and minimizes maintenance. Furthermore, robust oxide host combined with elastomeric encapsulation ensures outdoor durability and solid validation on solar‐exposure mapping.