Breakthrough Boost of Stokes Fluorescence from Er³⁺ in Perovskites for Flexible Temperature Sensing

Perovskites with ultra-low phonon energy have excellent radiation properties, while the population distribution of its luminescent initial state needs to be facilitated to further optimize the stokes fluorescence of Er³⁺ under high-energy photons excitation. Herein, UV excitability of Er³⁺ is remodeled by building an energy transfer channel from Sb³⁺ to Er³⁺ in Cs₂NaInCl₆ (CNIC) microcrystal to realize the enhancement of stokes fluorescence of Er³⁺. Under UV excitation, the breakthrough boost of Er³⁺ is observed in Cs₂NaInCl₆:Sb³⁺-Er³⁺ (CNIC:Sb-Er), and the sensitization coefficient from Sb³⁺ to Er³⁺ in CNIC is derived to be as high as 112. Moreover, CNIC:Sb-Er is embedded into functional fibers to enhance the crystal stability and the composite flexibility, which form fluorescence fibers with strong radiation transition probability. Finally, a high-precision temperature sensing is achieved based on FIR (fluorescence intensity ratios) technology, and the maximum relative sensitivities of CNIC:Sb-Er phosphors and CNIC:Sb-Er/PAN fibers reach 1.13 and 1.10% K⁻¹, respectively, indicating that CNIC:Sb-Er and CNIC:Sb-Er/PAN fibers have potential applications in optical temperature sensors.