Visible upconversion in Er³⁺/Yb³⁺ co-doped LaAlO₃ phosphors

The Er³⁺ doped and Er³⁺/Yb³⁺ co-doped LaAlO₃ phosphors have been synthesized by the combustion method and characterized their structural, morphological, elemental, vibrational and optical properties. The optical absorption and upconversion properties of the synthesized phosphors have been studied. Upon co-doping Yb³⁺ ions into Er³⁺:LaAlO₃, the blue, green and red upconversion emissions of Er³⁺ ions have been enhanced about ~20, ~54 and ~22 times, under 978nm laser excitation. The observed upconversion emissions could be due to excited state absorption in Er³⁺:LaAlO_3, whereas energy transfer is dominant mechanism in Er³⁺/Yb³⁺:LaAlO₃ phosphors. The tuning in the color emitted from the synthesized phosphors towards the green region has been found due to incorporation of the Yb³⁺ ions. With increase in the pump power, the color emitted from the co-doped phosphor is not tuned significantly, showing its applicability in making the green display devices.