Synthesis, luminescence properties and energy transfer of Ca2MgWO6:Cr3+, Yb3+ phosphors

An efficient near-infrared phosphor Ca2MgWO6:Cr3+,Yb3+ has been successfully prepared by solid state reaction in air. After co-doping with Cr3+ ion, Ca2MgWO6:Yb3+ can be efficiently excited by broadband UV light due to Cr3+ :(4)A(2) -> T-4(1)(P-4)) transition, and give intense near-infrared emission at similar to 980 nm owing to the effectively sensitized Yb3+:F-2(5/2) -> F-2(7/2) transition. Energy transfer from Cr3+ ion to Yb3+ ion in Ca2MgWO6 host was demonstrated to be mainly a resonant type via dipole-dipole mechanism, accompanied by a degree of down conversion process. The energy transfer efficiency from Cr3+ ion to Yb3+ ion was determined and the possible energy transfer processes in Ca2MgWO6:Cr3+,Yb3+ phosphor are proposed with simplified energy level diagrams. The Cr3+/Yb3+ co-doped Ca2MgWO6 phosphor converts ultraviolet (240-400 nm) photons into NIR (900-1050 nm) ones, which matches well with the optimal spectral response of silicon (Si) solar cells, and is expected to be promising as a luminescent solar concentrator for photovoltaic solar cells.