Energy transfer mechanisms in Yb3+ doped YVO4 near-infrared downconversion phosphor.

Upon ultraviolet (UV) light excitation, an intense near-infrared (NIR) emission of Yb³⁺ (²F_5/2→²F_7/2) around 980 nm is observed in YVO₄:Yb³⁺ phosphors. Owing to host absorption of YVO₄, a broad excitation band ranging from 250 to 350 nm is recorded when the Yb³⁺ emission was monitored, which suggests an efficient energy transfer from host to Yb³⁺ ions. The Yb³⁺ concentration dependence of the visible vanadate emission as well as the Yb³⁺ emission is investigated. The decay curve of vanadate emission is measured under the excitation of a 266 nm pulsed laser. The decay time of the vanadate emission at 500 nm is remarkably reduced by introducing Yb³⁺ ions, further verifying that the energy transfer from the vanadate host to the Yb³⁺ ions is very efficient. Cooperative energy transfer (CET) is discussed as a possible mechanism for the NIR emission. The YVO₄:Yb³⁺ phosphor can convert each UV photon into two NIR photons via CET, which has potential application in the high efficiency silicon-based solar cells. [ABSTRACT FROM AUTHOR]