Highly efficient Mn–Mn dimer activated phosphors for high-power near-infrared LED application

Abstract

Broadband near-infrared (NIR) phosphors have received increasing attention for fabricating NIR light sources. In this article, based on our predictions of heavy Mn-doped models obtained using DFT calculations, we successfully synthesize and characterize manganese-based magnetoplumbite-type La(Zn,Mn)Al₁₁O₁₉ phosphors, which crystallize into a hexagonal structure with space-group P6₃/mmc. Under excitation at 450 nm, it was found that LaZn_0.7Mn_0.3Al₁₁O₁₉ and LaZn_0.2Mn_0.8Al₁₁O₁₉ had the optimal emission intensity and the maximum quantum efficiencies were 99% and 55%, respectively. An anomalous near-infrared (NIR) emission band at ∼730 nm is observed for the LaZnAl₁₁O₁₉ host with heavy Mn²⁺ doping. The density functional theory calculations and transient and steady-state luminescence investigation suggest that this unusual NIR emission band comes from the Mn²⁺–Mn²⁺ dimers. Moreover, the as-prepared phosphor, being integrated into high-powered photonic devices, could operate at high temperature without degeneration, due to the great advantage of the phosphor-in-glass (PiG) approach. Consequently, our study not only develops a viable strategy for synthesising innovative NIR phosphors, but also sheds light on the development of high-power photonic devices and procedures.