La3+(lanthanide 3+) ion doping may significantly improve the photoluminescence properties of CaSi2O2N2:Eu2+, a potential yellow-green phosphor for ultraviolet or blue light-emitting diodes. The optimization mechanism was studied in detail by the case of La3+ doping. The La3+ ions could stabilize Ca2+ vacancies, inhibit the oxidization of Eu2+ to Eu3+, based on X-ray photoelectron spectroscopy, X-ray absorption near-edge structure measurements and first-principles calculations. Consequently, not only could the total number of activators be increased, but also the non-radiative transition probability between Eu2+ and Eu3+ could be reduced as a result of La3+ doping. It was also observed that the photoluminescence of CaSi2O2N2:Eu2+ phosphors could be enhanced by the addition of many La3+ ions, but not Sm3+ and Yb3+ ions, which confirmed the mechanism.

Optimization Mechanism of CaSi2O2N2 : Eu2+ Phosphor by La3+ Ion Doping. L.X.Yang, X.Xu, L.Y.Hao, Y.F.Wang, L.J.Yin, X.F.Yang, W.He, Q.X.Li: Journal of Physics D, 2011, 44[35], 355403