Effects of Ce3+ Doping in Green-Red Emitting Upconversion Nanoparticles

Controlling the luminescence of the rare-earth doped photon-upconversion materials is of particular importance for their practical applications. One of the most effective strategies for tuning the luminescent spectra is introducing extra dopants into the system to change the local symmetry of the crystal or get involved in the photon-upconversion process. In this work, completely opposite trends of green-to-red luminescent intensity ratio are observed when utilizing Ce3+ ions to manipulate emissions in Yb3+-Ho3+ and Yb3+-Er3+ doped upconversion nanoparticles. It is difficult to explain how the interaction happens between Ce3+ and Er3+ according to the 2-photon red upconversion emission process in Yb3+-Er3+ pair. We propose an explanation that the 5d state of Ce3+ is benefit for the increase of green-to-red luminescent ratio in Er3+. This work provides insight into mechanistic understanding of upconversion phenomena in nanoparticles and also enables exciting new opportunities of designing new materials for photonic applications.