Spectral Properties and Energy Transfer between Ce³⁺ and Yb³⁺ in the Ca₃Sc₂Si₃O₁₂ Host: Is It an Electron Transfer Mechanism?

The downshifting from Ce³⁺ blue emission to Yb³⁺ near-infrared emission has been studied in the garnet host Ca_2.8–2xCe_0.1Yb_xNa_0.1+xSc₂Si₃O₁₂ (x = 0–0.36). The downshifting does not involve quantum cutting, but one incident blue photon is transferred from Ce³⁺ to Yb³⁺ with an energy transfer efficiency up to 90% when x = 0.36 for the Yb³⁺ dopant ion. For x ≤ 0.15, a multiphonon-assisted electric dipole–electric quadrupole mechanism of energy transfer dominates, while for the highest concentration of Yb³⁺ employed, the electron transfer mechanism is confirmed. A temperature-dependent increase of the Ce³⁺ → Yb³⁺ energy transfer rate does not exclusively indicate the electron transfer mechanism. The application of the material to solar energy conversion is indicated.