Upconversion luminescence enhancement and color modulation in Yb³⁺/Er³⁺/Ln³⁺ (Ln = Tm, Ho) tri-doped YF₃ microrods

Intelligent regulation of energy transfer process among different rare earth ions doped in the matrix is an effective strategy to realize high-performance upconversion (UC) luminescence. Based on this, wheat ears like Yb³⁺/Er³⁺/(Tm³⁺, Ho³⁺) triple doped YF₃ microrods were fabricated via hydrothermal method, and the morphology, crystal structure, UC luminescence performance dependent on Tm³⁺/Ho³⁺ doping concentrations were studied. By comparing with the Yb³⁺, Er³⁺ co-doped YF₃ microrods, the UC luminescence intensity is enhanced in Yb³⁺/Er³⁺/(Tm³⁺, Ho³⁺) triple doped YF₃ samples due to the cross relaxation processes between Er³⁺ and Tm³⁺/Ho³⁺. Moreover, red emission is enhanced more significantly than green emission in YF₃: Yb³⁺, Er³⁺, Tm³⁺, which is contrary to that in YF₃: Yb³⁺, Er³⁺, Ho³⁺. The possible energy transfer upconversion mechanism involved is discussed in detail. Meanwhile, an adjustable emission color is easy to achieve via altering the doped Er³⁺/Tm³⁺/Ho³⁺ ion concentration. These studies on the UC luminescence enhancement mechanism of Yb³⁺/Er³⁺/(Tm³⁺, Ho³⁺) triple doped YF₃ microrods are expected to provide a reference for the development of high-efficiency luminescent materials.