Efficient monochromatic red, green, and blue up-converted luminescence from Yb3+-doped micro-phosphors co-doped with Er3+ or Tm3+ ions

• Yb3+-doped YVO4 and Y2O3 micro-phosphors co-doped with Tm3+ or Er3+ were prepared.
• Yb3+/Tm3+ co-doped YVO4 phosphor shows blue up-converted luminescence (ϕem 1.3%).
• Yb3+/Er3+ co-doped YVO4 phosphor shows green up-converted luminescence (ϕem 6.6%).
• Er3+/Yb3+ co-doped Y2O3 phosphor shows red up-converted luminescence (ϕem 14%).
• >94% spectral purity red, green or blue up-converted luminescence was obtained.

Yb3+-doped YVO4 and Y2O3 micro-phosphors co-doped with Tm3+ or Er3+ ions were prepared using a solid-state reaction method without the use of additional flux. Analysis of their crystalline properties indicates essentially complete inter-diffusion of the dopant ions into the host crystal with no evidence of impurity phases. The luminescence up-conversion properties of the micro-phosphors were investigated using 980 nm laser diode excitation. Blue up-converted luminescence centred at 474 nm associated with the 1G4 → 3H6 transition of Tm3+ is produced by the Tm3+/Yb3+ co-doped YVO4 phosphor, with an overall efficiency of luminescence up-conversion of 1.3%. The Er3+/Yb3+ co-doped YVO4 micro-phosphor produced two green up-converted luminescence emission bands centred at 526 nm and 554 nm corresponding to the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+, respectively, with a total efficiency of up-converted luminescence of 6.6%. In contrast with the green-emitting Er3+/Yb3+ co-doped YVO4-based phosphor, Er3+/Yb3+ co-doped Y2O3 micro-phosphors were produced displaying almost exclusively intense red up-converted luminescence associated with the 4F9/2 → 4I15/2 transition of Er3+, with efficiencies of luminescence up-conversion up to 14%. Micro-phosphors were produced for which the blue, green and red up-converted luminescence in each case accounts for >94% of the total up-converted luminescence emission.