Upconversion photoluminescence properties of SrY2O4:Er3+,Yb3+ under 1550 and 980 nm excitation

Er3+/Yb3+ co-doped SrY2O4 phosphors with high color purity and brightness were successfully synthesized via a solid-state reaction method. Luminescence spectrum studies showed that the main red peaks and the minor green peaks of upconversion emissions were located at approximately 634-681 nm and 543-570 nm, respectively, corresponding to the transitions of F-4(9/2)-> I-4(15/2) and S-4(3/2)-> I-4(15/2) of Er3+ ions. Under the excitation of 980 and 1550 nm lasers, the spectra of all of the samples exhibited similar peak positions but different intensities. When excited by the 980 nm laser, the intensity ratio of red to green emission increased with increasing Yb3+ doping concentration and decreased with increasing excitation power. In the case of 1550 nm excitation, the intensity ratio of red to green emission increased with increasing Yb3+ doping concentration and excitation power, thereby, improving the color purity of the red emission. The intensity of red emission was considerably stronger under 1550 nm excitation than that under 980 nm excitation. Therefore, the color of the proposed phosphors could be efficiently tuned by tailoring both the Yb3+ doping concentration and excitation power.