Preparation and properties of Li2ZnGeO4:Mn2+ green light emitting materials

Abstract

This study presents the synthesis and comprehensive characterization of Mn²⁺-doped Li₂ZnGeO₄ green-emitting long afterglow materials via a high-temperature solid-phase method, addressing the critical need for efficient luminescent materials in optoelectronic applications. Long afterglow materials have garnered significant attention for their ability to store and slowly release excitation energy, offering advantages in signal-to-noise ratio enhancement and background interference reduction compared to conventional luminescents. However, the development of germanate-based matrices with tailored luminescent centers remains underexplored. Herein, we demonstrate that Li₂ZnGeO₄ forms a single-phase monoclinic structure upon calcination at 1000 °C, with Mn²⁺ ions successfully substituting Zn²⁺ sites without altering the lattice framework. Photophysical analyses reveal that 0.5 mol% Mn²⁺ doping optimizes green emission (530 nm) originating from the ⁴T₁ → ⁶A₁ transition, with a notable afterglow duration of 1800 seconds attributed to defect-mediated electron/hole trap dynamics. The material exhibits high colour purity in the green region (CIE coordinates validated) and a forbidden bandgap of 3.21 eV, underscoring its potential for LED and optoelectronic applications. This work not only expands the family of germanate-based long afterglow materials but also provides mechanistic insights into Mn²⁺ luminescence tuning via lattice defect engineering, bridging the gap in comparative studies of Mn²⁺-doped matrices and highlighting the unique advantages of Li₂ZnGeO₄ for sustainable luminescence technology.