Enhanced down conversion of photons emitted by photoexcited ErxY2-xSi2O7 films grown on silicon

Photon cutting with efficiencies up to 400% is demonstrated in ErxY2-xSi2O7 films grown on Si and its concentration dependence is analyzed. The cutting is the result of cross-energy-transfer processes occurring within a single rare earth (Er3+) acting as both sensitizer and activator. Similarities with upconversion are revealed and possible applications in solar cells are discussed.