Multifunctional Applications of Bi3+/Eu3+ and Bi3+/Sm3+ Co-Doped Double Perovskite Phosphors in Temperature Sensing, Anti-Counterfeiting, Latent Fingerprint Visualization and WLED

In this work, double perovskite La2CaSnO6 (LCSO) doped with Bi3+, Bi3+/Eu3+, and Bi3+/Sm3+ ions were prepared via a high-temperature solid-state method. The optical properties and temperature-dependent luminescence of studied materials were systematically investigated. The emissions of co-doped materials can be tuned by efficient energy transfer from Bi3+ to Eu3+ or Sm3+ ions through electric dipole–quadrupole interaction or dipole–dipole interaction under UV excitation. Based on the fluorescence intensity ratio technique, the materials reached a maximum relative sensitivity of 1.43% K-1 at 513 K and a minimal thermal resolution of 0.48 K in LCSO:Bi3+, Sm3+ system. Furthermore, the tunable emission colors under different excitation wavelengths enabled the construction of a high‐security information encryption system based on ASCII coding, as well as high‐contrast fingerprint imaging. Besides, the WLED device fabricated by blending LCSO:0.02Bi3+, 0.1Eu3+ phosphor with a commercial green phosphor achieved a high color rendering index (Ra) of 89.9 and a low correlated color temperature (CCT) of 4170.89 K. These results demonstrate that the as-prepared Bi3+, Eu3+/Sm3+ doped LCSO phosphors with good performance metrics have promising potential in diverse applications.