Upconversion luminescence enhancement of β-NaYF4: Er3+/Ho3+ by introducing Ca2+ and multicolor tuning by 980 nm pulse excited

Abstract NaYF4:10Er/0.5Ho/30Ca@NaYF4 is designed to achieve up-conversion luminescence color adjustment under 980 nm excitation. Ho3+ doping enhances the red emission level of the system and changes the characteristic green emission into red emission. Importantly, Ho3+ doping increases the difference in pumping time between green and red excited states. Under short pulse-width laser excitation, the red excited state does not have enough time to be populated, which weakens the emission of red emission, and the ratio of green to red emission will change. It is an effective up-conversion luminescence enhancement method to change the symmetry of crystal field around lanthanide ions by doping Ca2+. The green and red emission intensities of NaYF4:10Er/0.5Ho/30Ca doped with 30% Ca2+ ions are 9.0 and 6.3 times higher than those of Ca2+ free samples, respectively.