Achieving Multicolor Upconversion Emissions without Changing Compositions

It is widely recognized that a proper way of adjusting fluorescence color is meaningful for pushing forward upconversion materials to be utilized in anti-counterfeiting, display and solid-state lightning applications. Traditional routes that apply different host materials and/or doping categories to adjust fluorescence color have shown large color region tunability yet have to rely on complex synthesis process accompanied with time and raw material consumption. In this work, in order to get a wide luminous color gamut without depending on reciprocating synthesis, we desinged and provided a high-sensitizer-concentration upconversion crystals, hexagonal NaLuF₄:Yb³⁺/Er³⁺ (50/2 mol%), whose red-to-green emission intensity ratio can be conveniently tuned from 2.69 to 4.96 by simply modulating excitation power densities. The promoted three-photon-population progress of red emission achieved by using an intensive excitation laser is considered to be responsible for the facile upconversion modulation. The results may provide new ideas for emission color control that based on external parameters in identical host and the greatly amplified excitation power-sensitivity of NaLuF₄:Yb³⁺/Er³⁺ (50/2 mol%) is highly potential for fluorescence anti-fake and colorful display applications.