Highly efficient energy transfer in Pr^3+, Yb^3+ codoped CaF_2 for luminescent solar converters

The codoping of CaF2:Pr3+ with Yb3+ ions is shown to lead to the formation of Pr3+/Yb3+ clusters, which can be attractive quantum cutting systems to enhance solar cells’ efficiency. Very high Pr3+ to Yb3+ energy transfer efficiencies (ETEs) are achieved for low Yb3+ and Pr3+ concentrations (ETE=97% in CaF2:0.5%Pr3+-1%Yb3+) confirming the short distance between Pr3+ and Yb3+ ions within clusters. A low Yb3+ concentration offers the advantage of drastically limiting the Yb3+ concentration quenching usually observed in other hosts where the Yb3+ concentration has to be larger to achieve a high ETE for solar cell applications.