High quantum efficiency achieved in novel multifunctional far-red-emitting LaLi0.333Ti0.667O3: Mn4+ double perovskite phosphor

The advancement of modern artificial plant cultivation necessitates the development of high-performance red-light sources precisely tailored to plant spectral absorption profiles. Such sources are crucial for improving crop yield and quality in contemporary agricultural practices. In this study, a far-red-emitting double perovskite phosphor LaLi 0.333 Ti 0.667 O 3 : Mn 4+ was successfully synthesized via a facile solid-state reaction method. Systematic investigations were conducted on the crystal structure, luminescent properties, and decay characteristics of the phosphor. Under 355 nm excitation, the optimized LaLi 0.333 Ti 0.667 O 3 : 0.3 mol% Mn 4+ phosphor demonstrates a prominent far-red emission peak at 726 nm, along with exceptional thermal stability, retaining 48.7 % of its room-temperature intensity at 420 K. Thermal quenching analysis yielded an activation energy (ΔE) of 0.388 eV. Remarkably, this phosphor achieves an ultrahigh internal quantum yield (QY) of 47 % within the 650–850 nm spectral range. The fabricated phosphor-converted light emitting diode (pc-LED) device exhibits precise spectral congruence with phytochrome far-red (P fr ) absorption (730 nm), indicating significant potential for photomorphogenetic regulation in agricultural applications through supplementary lighting strategies. Furthermore, due to its superior tissue penetration capability, this phosphor also shows promise for applications in non-invasive medical diagnostics.