Controlling Er³⁺ multiphoton upconversion by synergistically regulating energy transfer and cross-relaxation for...

The synergistic effect of various ions with optical properties is an important method to regulate the Er³⁺ ion upconversion luminescence process. However, the energy processes between them are complicated and difficult to separate, and it is challenging to clarify the results of each process when multiple ions are co-doped. Herein, a series of NaYF₄:Er³⁺ were synthesized by the low-temperature combustion method, and the luminescence color of Er³⁺ ions was modulated by doping Yb³⁺ ions and Tm³⁺ ions. The luminescence characteristics of the samples were studied by means of UC luminescence spectra and decay curves, and the luminescence mechanisms at different excitation wavelengths were discussed by the intensity-power test. Yb³⁺ ions acted as energy transfer centers to regulate the color of Er³⁺ ions, while Tm³⁺ ions acted as cross-relaxation centers to influence the upconversion energy process of Er³⁺ ions. Under the coordinated induction of Yb³⁺ and Tm³⁺ ions, the optimal red-light emission of Er³⁺ ions was achieved under 980 nm and 1550 nm excitation. Multiple excitation modes regulated multiple upconversion energy processes, and this series of phosphors exhibited multicolor upconversion luminescence performance, which is expected to be applied in the field of advanced optical anti-counterfeiting. This work provides a new idea for the study of upconversion energy process separation, and it is helpful to promote the design and development of high color purity upconversion phosphor material systems.