Thermochromic Cs2NaInCl6: Sb3+/Ln3+ (Ln = Er, Dy, Tb, Ho) phosphors for multifunctional applications

The intrinsic challenge to thermally responsive photoluminescent materials is pertaining to the limited thermal stability and reproducibility. Most prevailing photoluminescent agents suffer from constraints imposed by their frail chemical structure, rendering them fail to work at elevated temperatures for a long time. This inherent limitation curtails their utility within domains in anti-counterfeiting and encoded information storage. Herein, a series of double perovskite Cs2NaInCl6: Sb3+/Ln3+ (Ln = Er, Dy, Tb, Ho) phosphors were synthesized using the high-temperature hydrothermal method. Upon ultraviolet light illumination, the blue emission band of self-trapped excitons (STEs) and intrinsic emissions of Ln3+ are observed. In light of the variations in thermal quenching levels of the two emission centers and the effect of temperature on the lifetime of Ln3+, multi-mode thermometers with superior sensitivity are established. Moreover, they also can be used in anti-counterfeiting and encoding information storage, relying on the significant temperature-dependent color variation, excellent thermal stability and repeatability. The unique thermochromic properties and satisfactory stability of Cs2NaInCl6: Sb3+/Ln3+ (Ln = Er, Dy, Tb, Ho) phosphors bring forward a new concept of developing multi-mode thermometers and reliable information encryption systems with the application of thermochromic materials.