Energy transfer and charge compensation of Ba2ZnGe2O7:Tb3+,Eu3+ phosphors for white LEDs†

Abstract

Light-emitting diodes are considered the next-generation lighting technology due to their high efficiency, reliability, and energy savings. However, single-phase color-tunable phosphors with excellent luminous properties are still urgently needed. Herein, series of Tb³⁺/Eu³⁺ co-doped Ba₂ZnGe₂O₇ phosphors were synthesized via a high-temperature solid-state reaction. The crystal structure, chemical composition, photoluminescence properties, and energy transfer process of the obtained phosphors were deeply investigated. To optimize the luminous efficiency of the phosphors, alkali metal ions were doped into the phosphors to provide charge compensation, leading to a significant enhancement in photoluminescence intensity. By modulating the Tb³⁺/Eu³⁺ ratio, the emission color of the Tb³⁺/Eu³⁺ co-doped Ba₂ZnGe₂O₇ phosphors could be easily tuned from green to red. The efficient Tb³⁺ → Eu³⁺ energy transfer in Ba₂ZnGe₂O₇ phosphors was determined to be a quadrupole-quadrupole interaction. The color-tunable Ba₂ZnGe₂O₇:Tb³⁺,Eu³⁺ phosphors exhibited excellent optical properties and thermal stability, demonstrating great potential for applications in the next generation of lighting technology.