Enhanced photoluminescence and phosphorescence properties of green phosphor Zn2GeO4:Mn2+via composition modification with GeO2 and MgF2

Abstract

A green long-lasting phosphorescence (LLP) phosphor Zn₂GeO₄:Mn²⁺ (ZGOM) has been synthesized by a solid-state method at 1100 °C in air. The luminescence intensity has been improved up to 9 and 6 times through mixing GeO₂ and MgF₂ into the composition, respectively. The phosphorescence duration of the sample has been prolonged to 5 h. The phosphor, composed of a mixture of Zn₂GeO₄ (ZGO), GeO₂, and MgGeO₃ phases, emits enhanced green luminescence with a broad excitation band between 250 nm to 400 nm. Under identical measurement conditions, the optimized phosphor ZGOM has a higher emission intensity and shows longer wavelength emission than those of the commercial green LLP phosphor SrAl₂O₄:Eu,Dy (SAOED) under an excitation at 336 nm. The quantum yield of the sample modified by GeO₂ and MgF₂ is as high as 95.0%. Understanding of the formation mechanism for enhancement of emission intensity and prolonging of phosphorescence duration of ZGOM is fundamentally important, which might be extended to other identified solid-state inorganic phosphor materials for advanced properties.