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.