<p>YPO₄ nanophosphors doped with Tb³⁺, Ce³⁺, and co-doped with Tb³⁺/Ce³⁺ were synthesized via a hydrothermal method, and the effects of rare-earth doping on their structural and optical properties were comprehensively examined. A combination of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy, along with first-principles calculations, was used to investigate the crystal structure and electronic properties. The optimal doping concentrations for Tb³⁺ and Ce³⁺ were determined to be 13% and 1%, respectively. Higher doping levels led to concentration quenching attributed to electric dipole–dipole interactions. Theoretical calculations confirmed that YPO₄ possesses a direct bandgap of 5.88&#xa0;eV. Energy transfer between Ce³⁺ and Tb³⁺ ions occurs primarily through an electric dipole–electric quadrupole mechanism, with a transfer efficiency reaching 50%. The co-doped YPO₄:Tb³⁺,Ce³⁺ exhibited excellent thermal stability, highlighting its potential for applications in high-temperature fluorescence thermometry and fingerprint recognition. This work provides both theoretical insights and experimental support for advancing rare-earth-doped nanophosphors in anti-counterfeiting and biometric technologies.</p> Graphical Abstract <p></p>