Enhanced energy transfer and near-infrared luminescence by crystal field regulation in Zn3Ga2GeO8:Cr3+,Yb3.

Abstract

Near-infrared (NIR)-emitting phosphors with broadband absorption from ultraviolet to visible light have been considered significant spectral converter materials for solar cells. In this work, NIR phosphor Zn3Ga2GeO8 (ZGGO):Cr3+,Yb3+ spinel solid solutions were synthesized using the classical high-temperature solid-state method. With an increase in the doping concentration of Cr3+ ions in ZGGO:Cr3+,Yb3+, a more distorted octahedron appeared around Cr3+ ions, which increased crystal field splitting. This process was accompanied with a broadening of NIR emission from Cr3+ 4T2 → 4A2 transition and enlarged the overlap area between the absorption spectrum of Yb3+ and the emission spectrum of Cr3+, resulting in an efficient energy transfer between Cr3+ and Yb3+. In the case of high-concentration Cr3+ doping, the near-infrared luminescence intensity of Yb3+ was more than 8 times that of low-concentration doped Cr3+. Therefore, it is proposed that the Cr3+,Yb3+ co-doped ZGGO phosphor is a potential spectral convert materials for silicon-based solar cells and thereby improves photovoltaic conversion efficiency.