Surface Vibration-Mediated and Multiphonon Relaxation-Assisted Antithermal-Quenching Shortwave Infrared Emission in Ho-Based Double Perovskite With Long Lifetime

Thermal quenching generally predominates in Er³⁺ 1540 nm luminescence quenching at elevated temperatures, due to intensified lattice vibration and efficient overtone vibrational relaxation by O─H stretch. This issue impedes practical device applications of shortwave infrared Er-doped phosphors. Herein, with the mediation of surface vibrational phonons, anti-thermal quenching of Er³⁺ 1540 nm emission is reported in (220)-dominated Er³⁺-doped Cs₂NaHoCl₆ double perovskite. The downshifting emissions can be boosted with rising temperatures from 303 to 543 K, reaching 225%@483 K of the initial intensity at 303 K, accompanied with a long lifetime of 33.02 ms at 483 K. By combining temperature-dependent in situ Raman and Fourier transform infrared spectroscopies with the excited-state dynamics results, the coordination role of water molecules is verified, serving as promoters instead of quenchers on the (220) facet at high temperatures. Furthermore, efficient energy transfer from Ho³⁺ to Er³⁺ enables intense 1540 nm emission with a photoluminescence quantum yield of 78.1% under 450 nm excitation. Finally, a compact thermally stable phosphor-converted light-emitting diode (LED) is designed as a narrowband shortwave infrared light source with a blue LED chip. This work pushes the improved understanding of achieving thermal-enhanced Er³⁺ luminescence for potential broad applications.