Enhance upconversion photoluminescence intensity by doping Li+ in Ho3+ and Yb3+ codoped Y2O3 nanocrystals

Infrared-to-visible upconversion emission spectrum is investigated in Li + , Ho 3+ and Yb 3+ codoped Y 2 O 3 nanocrystals. By adding Li + ion to the Y 2 O 3 :Ho 3+ /Yb 3+ nanocrystal, the upconversion emission intensity is found being significantly enhanced comparing with that without Li + ion. The two reasons for this enhancement are discussed: one is because of the modification of the local symmetry of the Ho 3+ ion, and the other is because of the reducing number of OH groups. This indicates Li + ion would be a wonderful photoluminescence intensifier for rare-earth.