Synthesis and down-conversion luminescence of Ba$_4$Y$_3$F$_{17}$:Yb:Pr solid solutions for photonics

Singlephase powders of Ba$_4$Y$_3$F$_{17}$:Yb:Pr solid solutions with an average agglomerate size of 400 nm were synthesized by coprecipitation from aqueous solutions. It was shown that the down-conversion mechanism in the investigated samples was quantum cutting, with one photon absorbed by Pr$^{3+}$ ions resulting in two photons emitted by Yb$^{3+}$ ions. At first, overall the external quantum yield of down-conversion luminescence measured appeared to be relatively high, with a maximum value of 2.9 % for the Ba$_{4}$Y$_{3}$F$_{17}$: Pr(0.1 %):Yb(10 %) sample. It makes this compound promising for Si-based solar cells efficiency enhancement.