Self deep red luminescence in NaLaCaWO6 double perovskite, properties regulation via Er3+ doping, and applications in favorable optical thermometry with ultra high relative sensitivity and plant lighting

Self deep red emission was found for the first time in NaLaCaWO₆ double perovskite which was synthesized via solid-state reaction, and the luminescence was effectively enhanced and regulated via Er³⁺ doping. A comprehensive analysis of the calcination atmosphere dependent photoluminescence, X-ray photoelectron spectroscopy, and electron paramagnetic resonance revealed that the deep red luminescence is particularly related to oxygen defects of oxygen interstitials. The plant growth lighting and the optical thermometry performance of the materials were systematically investigated. Under 360 nm or 502 nm excitation, the pristine NaLaCaWO₆ exhibits deep red emission at 690 nm that nicely matches the photosensitive pigment (P_FR) essential for plant growth. The deep red luminescence of NaLaCaWO₆ was 230 % increased by Er³⁺ doping. Moreover, deep red emission of the host and green emission of the Er³⁺ shows extinguished different temperature depend luminescence behavior, and dual-mode optical thermometry with ultra high relative sensitivity (S_r) was built based on the materials. Remarkably, the maximum S_r based on the fluorescence intensity ratio (FIR) mode reached 3.84 % K⁻¹ (498 K), and maximum S_r is as high as 13.1 % K⁻¹ (548 K) when based on the fluorescence lifetime (FL) mode. The results indicate that the NaLaCaWO₆:Er³⁺ phosphor shows promising potential application in the field of plant growth and optical temperature sensing.