Efficient down- and up-conversion of Pr3+–Yb3+ co-doped transparent oxyfluoride glass ceramics

Pr3+ and/or Yb3+ doped transparent oxyfluoride glass ceramics (GCs) containing CaF2 nanocrystals were fabricated and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Judd–Ofelt (J–O) intensity parameters, radiative transition probability, radiative lifetimes, and branching ratios of Pr3+ have been calculated from the absorption spectra. Upon 470 nm excitation, Pr3+ doped GCs yield intense visible-near infrared (NIR) luminescence corresponding to the 3P0 → 3H6, 3P0 → 3F2,3,4, 3P1 → 1G4, 1D2 → 3H5, and 1D2 → 3F4 transitions, respectively. With the addition of Yb3+ ions, NIR down-conversion (DC) emissions at 976 nm (2F5/2 → 2F7/2) were achieved, due to efficient energy transfer (ET) from Pr3+ to Yb3+. Underlying mechanism for the NIR-DC is analyzed in terms of static and dynamic photoemission and monitored excitation spectra. The maximum quantum efficiency from Pr3+:3P0 to Yb3+:2F5/2 is calculated to be 153%. In comparison, intense up-conversion emissions at 489, 545, 606, and 651 nm have been obtained in Pr3+–Yb3+ codoped glass and GCs under 980 nm excitation, which is ascribed to be two-photon involved ET from Yb3+ to Pr3+.

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► Pr3+ and/or Yb3+ doped transparent oxyfluoride glass ceramics (GCs) containing CaF2 nanocrystals were fabricated.
► Efficient near-infrared (NIR) cooperative downconversion (DC) has been demonstrated in Pr3+–Yb3+ co-doped transparent oxyfluoride glass ceramics upon broadband ultraviolet light excitation.
► Underlying mechanism for the NIR-DC is analyzed in terms of static and dynamic photoemission and monitored excitation spectra.
► The development of Pr3+–Yb3+ co-doped transparent oxyfluoride glass ceramics could open up a potential possibility in realizing high efficiency photovoltaic cells.