Spectral Regulation in Cs₂PtCl₆ Double Perovskite via Low-Temperature and High-Pressure Engineering for Advanced Optical Thermometry and Manometry

To build a bifunctional luminescent platform for optical thermometry and manometry, the Cs2PtCl6 double perovskite was synthesized. Upon 468 nm excitation, the designed compound emitted bright red light centered at ≈675 nm, originating from the 3T1g,3T2g → 1A1g transition of Pt4+, whose fluorescence intensity and bandwidth are highly temperature dependent. Moreover, the temperature-dependent decay curves of the developed Cs2PtCl6 double perovskite were measured to explore its application in optical thermometry, of which its maximum relative sensor sensitivity is 1.21% K-1, with the operation range of 100-310 K. Furthermore, the impact of pressure on the phase structure and luminescence behaviors of the Cs2PtCl6 double perovskite was also discussed. The pressure-dependent Raman spectra clarified that the synthesized compound possesses a stable phase structure at high pressure. Furthermore, Cs2PtCl6 double perovskite exhibits distinct spectral blue-shift at high pressure. Importantly, as pressure increases (i.e., 0-5.67 GPa), the emission band centroid and full width at half-maximum (fwhm) are both linearly dependent on pressure, resulting in high pressure sensitivities of dλ/dp = 7.19 nm/GPa and dfwhm/dp = 4.95 nm/GPa, respectively. Our finding manifests that the luminescence characteristics of the Cs2PtCl6 double perovskite can be efficiently regulated via low temperature and high pressure, enabling its applications in optical thermometry and manometry.