Real-time RGB color-tunable upconversion luminescence using a single excitation wavelength

Abstract Real-time color-tunable upconversion luminescence of lanthanide ions has recently attracted increasing attention. To date, at least two different excitation wavelengths are required to obtain tunable upconversion colors containing the three-primary-color components (Red-Green-Blue). In this work, for the first time, we demonstrate that it is possible achieving tunable three-primary-color upconversion luminescence using a single excitation wavelength, on the basis of the photon-order dependent uponversion nature. A core-shell-shell nanocrystal was synthesized, with rational designed compositions of Er/Yb and Tm/Yb in the core and the outermost shell, respectively, responsible for the green/red and blue emissions. By increasing the power density of the 980 nm continuous-wave excitation laser, the color of the emitted luminescence of the core-shell-shell nanocrystal evolved as green → red → blue, corresponding to 2 → 3 → 4-photons involved in the upconversion process.