Yellowish-green upconversion emission in Ho3+: SrY2O4 nanophosphors for display applications

Ho3+:SrY2O4 nanophosphors have been prepared by solid state reaction technique. The upconversion (UC) emission spectra of the synthesized nanophosphors have been recorded upon 980 nm diode laser excitation. The UC emission spectra shows intense green and red emission bands similar to 542 nm and similar to 661 nm which are assigned to the F-5(4)/S-5(2)-> I-5(8) and F-5(5)-> I-5(8) electronic transition of the Ho3+ ions. The mechanism involved in the origination of UC emission bands are well explained by the energy level diagram and pump power dependence study. The emission colour purity of the present nanophosphors have been analysed by the CIE chromaticity diagram. The developed nanophosphors can be used in making NIR to visible upconverter and display devices.