Luminescence properties and excitation process of a near-infrared to visible up-conversion color-tunable phosphor

Further investigation of previously reported color-tunable NaNbO3-based up-conversion phosphor doped with Er3+, Yb3+, and Al3+ (NaNbO3:Er,Yb,Al) was undertaken. Color tuning is achieved by variation of the relative intensity of the red/green emission, which is dependent on the pulse width of the near-infrared (980 nm) excitation. The chromaticity of emissions ranging from green to reddish-yellow with a change of pulse duration from 50 to 2400 μs is wider than that of the reference compound LaGaO3:Er,Yb, and is not influenced by the excitation intensity. It was elucidated that the green and red emissions occur via different excitation routes, of which the latter is characterized by a much slower build-up of emission.