Facile microwave-assisted synthesis of Zn 2 GeO 4 :Mn 2+ , Yb 3+ uniform nanorods and near-infrared down-conversion properties

Abstract Germanates have potential applications in electroluminescent fields. Herein, we report a simple strategy for the rapid synthesis of near-infrared (NIR) down-conversion Zn1.96-xGeO4+1/2x:Mn0.04Ybx phosphors using the microwave-assisted hydrothermal method. This method is facile, rapid, surfactant-free and environmentally friendly. In the Zn2GeO4 lattice, intrinsic defect transitions and Mn2+ ions act as broadband spectral sensitizers by absorbing UV–Vis (280–500 nm) photons and transferring the absorbed energy to Yb3+ centers in a cooperative down-conversion process. Efficient energy transfer is reflected by a sharp decrease in the excited state lifetime and green photoluminescence (PL) from tetrahedrally coordinated Mn2+ with increasing Yb3+ concentration. The possible formation mechanism for Zn1.96-xGeO4+1/2x:Mn0.04Ybx nanorods has been presented. PL spectroscopic characterizations show that pure Zn2GeO4 sample shows a blue emission due to defects, while Zn2GeO4:Mn2+ phosphors exhibit a green emission corresponding to the characteristic transition of Mn2+ (4T1 → 6A1) under the excitation of UV. The Yb3+ acceptor is then the source of NIR emission at a wavelength of ∼1000 nm. These phosphors are promising for applications in solar spectral down-conversion.