Down-shifting and down-conversion emission properties of novel CdO–P2O5 invert glasses activated with Pr3+ and Pr3+/Yb3+ for photonic applications

Abstract

The down-shifting and down-conversion emission properties of novel CdO–P2O5 invert glasses activated with Pr3+ and Pr3+/Yb3+ were respectively studied. The down-shifting emission spectra of Pr6O11 singly doped glasses upon 443 nm excitation (Pr3+: 3H4 → 3P2), displayed the feature Pr3+ transitions in the visible and near-infrared (NIR) regions, reaching the optimum intensity at 0.7 and 0.3 mol% of Pr6O11, respectively. The emission tonality can be adjusted from the reddish-orange to orange-pink region, depending on the Pr6O11 content. Such fact coupled with the superposition of the blue light excitation might be attractive for white light-emitting diodes (W-LEDs) applications. The cross-relaxation processes involved between Pr3+-Pr3+ pairs seem to be mediated by an electric quadrupole-quadrupole interaction, as revealed by the Inokuti-Hirayama model. The emission spectra of the Pr6O11 and Yb2O3 doped glasses upon 443 nm excitation showed, in addition to the Pr3+ related transitions, a band at 977 nm associated with the Yb3+: 2F5/2 → 2F7/2 transition, which gradually grows at expenses of non-radiative energy transfer from Pr3+. This process might lead to a down-conversion (quantum cutting) emission with theoretical quantum efficiencies up to 144%. Analysis complemented by the Inokuti-Hirayama or Dexter model revealed that the non-radiative Pr3+ → Yb3+ energy transfer process arisen from Pr3+: 3P0 and 1D2 levels are most likely dominated by electric dipole-dipole and quadrupole-quadrupole interactions, respectively. The global emission properties suggest that the Pr3+ and Pr3+/Yb3+ activated CdO–P2O5 invert glasses might be interesting for WLEDs and crystalline silicon (c-Si) solar cell applications.