Color control and white light generation of upconversion luminescence by operating dopant concentrations and pump densities in Yb3+, Er3+ and Tm3+ tri-doped Lu2O3nanocrystals

Abstract

We synthesized a series of Yb³⁺, Er³⁺ and Tm³⁺ tri-doped Lu₂O₃ nanocrystals with various dopant concentrations by the hydrothermal approach. Due to a unique electronic state at the top of the valence band, Lu₂O₃ based materials exhibit intense upconversion luminescence involving ¹G₄ → ³H₆ of Tm³⁺ in blue, (²H_11/2, ⁴S_3/2) → ⁴I_15/2 in green and ⁴F_9/2 → ⁴I_15/2 in red of Er³⁺ upon near infrared excitation at 980 nm. The variation of upconversion spectra and color points with dopant concentrations and pump densities are studied in detail on the basis of energy transfer processes. An ideal white upconversion light with color coordinates of (0.327, 0.339) is obtained by controlling the intensity of red, green, and blue emission in Lu_1.906Yb_0.08Er_0.008Tm_0.006O₃nanocrystals under a pump density of 8 W cm⁻². Based on the present experimental data, we may predict the dopant concentrations and pump densities for any color point within or around the white light region in the tri-doped Lu₂O₃ nanocrystals.