Blue and white upconversion emissions of rare-earth ions-doped oxyfluoride phosphors

摘要

A blue emitting upconversion phosphor based on Yb~(3+) and Tm~(3+ )codoped oxyfluoride is reported. Under the excitation of a single 980nm diode laser with the power density of 5.56W/cm~2, the upconversion luminescence brightness can reaches to 13053 mcd/m~2, which is much stronger than that of commercial Y_2O_2S:Yb, Tm phosphors (8194 mcd/m~2). The research of upconversion mechanism indicates that cooperating sensitization dominates the emissions at 479 and 645 nm, while the emission at 454nm results from the combination of cooperating sensitization and phonon-assisted energy transfer from Yb~(3+) to Tm~(3+). Also, bright upconversion white light is obtained by tri-doping of Er~(3+), Tm~(3+) and Yb~(3+). Because the blue (main emission at 479 nm), green and red emissions are two-photon process, the white light is not sensitive to the pumping power.