The incorporation of Ge4+ enhances the performance of La2MgSnO6:Mn4+ double perovskite phosphors

Abstract

Red-emitting phosphors activated by Mn⁴⁺ have gained increasing attention for applications in solid-state lighting and plant-growth illumination, owing to their excellent spectral match with both LED emission and the photosynthetically active radiation region. In this study, Mn⁴⁺-activated La₂MgSnO₆ phosphors were synthesized via a conventional high-temperature solid-state reaction, and Ge⁴⁺ was incorporated as a co-dopant to tailor their luminescent behavior. The samples exhibit a broad excitation band from 300 to 550 nm and a sharp red emission centered at 705 nm under 366 nm excitation. With increasing Ge⁴⁺ content, the emission intensity and quantum yield first increased and then decreased, reaching a maximum at 30 mol% Ge⁴⁺. At this composition, both fluorescence lifetime and thermal stability were significantly improved, while the emission wavelength remained nearly constant. These enhancements are attributed to Ge⁴⁺-induced local lattice modulation, which optimizes the coordination environment of Mn⁴⁺ ions, suppresses non-radiative losses, and facilitates radiative transitions. The results reveal that Ge⁴⁺ co-doping offers an efficient lattice-engineering strategy for improving the performance of Mn⁴⁺-activated La₂MgSnO₆ and provide valuable insight into the design of high-efficiency red phosphors.