Tunable luminescence and energy dynamics in Tb3+, Eu3+ co-doped Y2Zr2O7 phosphors for high contrast latent fingerprint imaging

Colour-tunable phosphor materials have gained significant attention for applications in solid-state lighting, displays, optical sensors, and security devices. The phosphors doped with rare-earth ions are particularly attractive due to their diverse electronic transitions and excellent optical stability. However, controlling the energy transfer processes that enable colour tunability remains challenging. This study investigates colour-tunable luminescence and energy transfer dynamics in Tb 3+ , Eu 3+ co-doped Y 2 Zr 2 O 7 phosphors. Powder X-ray diffraction and Rietveld refinement confirmed the formation of a single-phase defective fluorite structure without any secondary phases. Diffuse reflectance spectroscopy revealed an absorption edge at ~206 nm corresponding to a direct bandgap of 5.39 eV. Photoluminescence under 254 and 268 nm excitation, the co-doped sample (Y 1.95 Tb 0.02 Eu 0.03 Zr 2 O 7 ) exhibited green ( 5 D 4 → 7 F 5 , Tb 3+ ) and dominant red ( 5 D 0 → 7 F J (J=1-4) , Eu 3+ ) emissions, respectively. No energy transfer (ET) from Eu 3+ →Tb 3+ was observed, whereas efficient ET from Tb 3+ →Eu 3+ occurred with efficiencies of 25% and 10% under λ ex =377 and λ ex = 486 nm respectively. The maximum internal quantum efficiency of value 27% was achieved for the Eu 3+ -doped sample (Y 1.97 Eu 0.03 Zr 2 O 7 ) under λ ex = 254 nm. Thermoluminescence glow curves revealed five trap levels (0.4–1.22 eV), confirming the coexistence of shallow and deep traps within the bandgap. The chromaticity coordinates showed excitation-dependent colour tunability from green to red with improved colour purity. Furthermore, the practical utility of the phosphor was evaluated through latent fingerprint detection on various surfaces. Notably, high-resolution level-3 ridge features were distinctly resolved, positioning Y 1.95 Tb 0.02 Eu 0.03 Zr 2 O 7 as a promising multifunctional candidate for high contrast fingerprint imaging. • Tb 3+ , Eu 3+ single and co-doped Y 2 Zr 2 O 7 phosphors were successfully synthesized via combustion method with a pure defective fluorite structure. • DRS measurements confirmed the suppression of Tb IV absorption after reduction treatment, leading to enhanced luminescence. • Photoluminescence studies revealed strong green (Tb 3+ ) and red (Eu 3+ ) emissions with efficient ET from Tb 3+ → Eu 3+ under λ ex = 377 nm. • Quantum yield analysis showed highest efficiency value of 27% for Eu 3+ -doped samples. • Y 1.95 Tb 0.02 Eu 0.03 Zr 2 O 7 (Co-doped) sample enabled latent fingerprint visualization resolving levels 1-3 ridge features with highest image contrast of 0.99 under 254 nm UV excitation.