Near-infrared quantum cutting of Pr3+-Yb3+ co-doped CaF2 with broadband sensitization by Eu2+ ions

We achieved a quantum cutting process in Pr 3+ -Yb 3+ co-doped CaF 2 that converts one visible photon into two near-infrared photons matching the silicon band gap. In this study, the quantum cutting process between Pr 3+ and Yb 3+ was experimentally verified through comparative analysis of the normalized absorption spectrum of Pr 3+ and the near-infrared excitation spectrum of Yb 3+ . Fluorescence lifetime measurements at the optimal doping concentration revealed an energy transfer efficiency of 60.99% from Pr 3+ to Yb 3+ . Temperature-dependent luminescence spectroscopy further estimated the luminescence efficiencies as 64.49% (Pr 3+ ) and 71.41% (Yb 3+ ). Based on these results, the theoretical quantum efficiency of the Pr 3+ →Yb 3+ system was obtained to be about 112.26%, confirming the occurrence of efficient photon down-conversion. Considering the limited energy gain from sunlight due to the narrow-band absorption of Pr 3+ by f-f forbidden transition, Eu 2+ ions were employed to perform broadband sensitization on the quantum cutting process of Pr 3+ -Yb 3+ . Studies have suggested that the incorporation of Eu 2+ can effectively assimilate the 250-400 nm band and transfer energy to Pr 3+ and Yb 3+ , causing them to emit stronger near-infrared spectra. These developed materials are capable of converting ultraviolet-visible photons into near-infrared photons matching the silicon bandgap, which reduces energy loss caused by spectral mismatch and has promising applications in silicon-based photovoltaics.