Enhanced temperature sensing in lead-free Cs3Bi2Cl9 perovskite co-doping Yb3+/Er3+ for optical thermometry application

A simple and rapid grinding method for preparing Er 3+ -doped and Er 3+ /Yb 3+ co-doped Cs 3 Bi 2 Cl 9 upconversion phosphors was developed. We avoid to employ strong acids as reaction solvents, aligning with the principles of green chemistry. By controlling the thermal treatment temperature and adding BiCl 3 , a reversible phase transformation process between Cs 3 Bi 2 Cl 9 and Cs 3 BiCl 6 perovskite phosphors was achieved. The Er 3+ /Yb 3+ co-doped Cs 3 Bi 2 Cl 9 phosphors emit green light under 980 nm excitation, whereas Cs 3 BiCl 6 phosphors emit red light. Their temperature sensing performance was tested through variable-temperature processes. Compared to Er 3+ -doped Cs 3 Bi 2 Cl 9 phosphors, the co-doped Er 3+ /Yb 3+ phosphors have a higher relative sensitivity of 1.60 % K −1 . Compared to previously reported materials, Cs 3 Bi 2 Cl 9 phosphors show enhanced sensitivity in temperature sensing. The study demonstrates that lead-free halide perovskites’ unique color-tunability not only underscores the innovativeness of this synthetic strategy but also provides a significant technological foundation for temperature sensing applications. Given their environmental friendliness and facile preparation process, these phosphors possess notable advantages for industrial production and hold promise as potential candidates for next-generation high-performance phosphor materials.