Enhanced upconversion luminescence of NaYF4:Yb, Er microprisms via La3+ doping

A series of beta-NaYE4: Yb, Er micro-prisms codoped with La3+(0-30 at%) were synthesized via hydrothermal process. Upon 980 nm excitation at room temperature, 20 mol% La3+ codoped sample shows a maximum upconversion emission intensity. Excitation power density dependencies of UC luminescence and the decay curves were investigated. The UCPL decay is evidently monoexponential for all samples and La3+ doping did not significantly change the decay time. In this particular case, we found the napierian logarithm of the UC emission intensity (lnI) had a good linear relationship with the cell lattice parameters. This correlation may be helpful for design and fabrication of high performance upconversion materials.