Near-infrared to visible photon up-conversion in V3+, Re4+ co-doped Cs2NaYCl6

Cs2NaYCl6 co-doped with V3+ and Re4+ was studied by optical absorption and luminescence spectroscopy. In the cubic host lattice both dopant ions substitute for the octahedrally coordinated Y3+. Visible by eye red up-conversion luminescence centered around 14 000 cm−1 is observed upon near-infrared excitation within the energy range from 10 000 to 12000 cm−1 between 15 and 300 K. For V3+ 3T2g excitation at 11 350 cm−1, the efficiency of this up-conversion process increases with increasing temperature. An energy transfer step from V3+ to Re4+ followed by an energy transfer up-conversion process on the Re4+ system is shown to be the likely mechanism responsible for this phenomenon.