Ultrasensitive Pressure‐Responsive Upconversion Luminescence in Cs 2 NaBiCl 6 :Yb 3+ /Mn 2+ Optical Manometry

ABSTRACT Current optical manometers that rely on ultraviolet (UV) excitation suffer from low pressure sensitivity, high cost of UV lasers, and severe photoluminescence interference caused by spectral overlap between the excitation/emission light and background fluorescence. To address these issues, we herein explored a kind of novel optical manometry based on Cs 2 NaBiCl 6 :Yb 3+ /Mn 2+ double perovskite, exhibiting pressure‐sensitive broadband upconversion emission that originated from Yb 3+ ‐Mn 2+ dimers. By virtue of near‐infrared (NIR) energy transfer from Yb 3+ to Yb 3+ ‐Mn 2+ dimers, a linear upconversion pressure sensitivity as high as 15.03 nm/GPa was achieved upon 980‐nm excitation, which is over forty times higher than that of commercial manometer Ruby (0.36 nm/GPa) and traditional lanthanide (Ln 3+ )‐doped upconversion luminescence (UCL) phosphors (∼0.20 nm/GPa). Through in situ pressure‐dependent structural analysis, it was demonstrated that such exceptional pressure‐sensing performance stems from the soft lattice of Cs 2 NaBiCl 6 , which has a significantly low bulk modulus of 23.69 GPa. In addition, the pressure‐dependent Raman spectra further verified the stability and repeatability of Cs 2 NaBiCl 6 :Yb 3+ /Mn 2+ at extreme conditions. This work develops an ultrasensitive pressure‐responsive upconversion luminescent material, establishing a reliable visual optical strategy for high‐precision pressure monitoring in versatile scenarios.