Room‐Temperature Wavelength‐Tunable Single‐Band Upconversion Luminescence from Yb³⁺/Mn²⁺ Codoped Fluoride Perovskites ABF₃

In contrast to well‐known multiple and fixed upconversion (UC) emission bands from lanthanide (Ln³⁺) ions activated luminescent materials, room temperature wavelength‐tunable single‐band UC emissions are designed and demonstrated in Ln³⁺ ions/transition metal Yb³⁺/Mn²⁺ codoped fluoride perovskites ABF₃ (A = K⁺, Rb⁺, and Cs⁺; B = Mg²⁺, Zn²⁺, and Cd²⁺). Upon 976 nm laser excitation, the perovskites ABF₃:Yb³⁺, Mn²⁺ exhibit intense single band UC emission centered at 550–610 nm depending on the substitution of the A⁺ and / or the B²⁺ species in ABF₃. Crystal structure and luminescent properties analysis show that the UC emission should originate from the transitions of super‐exchange coupled Yb³⁺–Mn²⁺ pair. The Stokes and UC emission properties, UC luminescence decay behaviors, as well as temperature dependent UC emission properties of ABF₃:Yb³⁺, Mn²⁺ are investigated and discussed in detail. The intense room (or high) temperature UC emission and ultralong UC decay lifetimes (≈25–45 ms) clearly reveal that the perovskites ABF₃:Yb³⁺, Mn²⁺ can be potentially applied in the fields of time‐resolved luminescence imaging, lighting, and solid state lasers.