Color-tunable upconversion luminescence and prolonged Eu3+ fluorescence lifetime in fluoride KCdF3:Yb3+,Mn2+,Eu3+via controllable and efficient energy transfer

Abstract

Due to the lack of intermediate levels and the large energy mismatch with Yb³⁺, the achievement of efficient upconversion (UC) of Eu³⁺ is a great challenge. Herein, intense UC emission of Eu³⁺ is demonstrated via controllable and efficient unidirectional energy transfer from Yb³⁺–Mn²⁺ dimers in perovskite fluoride KCdF₃:Yb³⁺,Mn²⁺,Eu³⁺ synthesized by a facile solvothermal method. The UC emission color of KCdF₃:Yb³⁺,Mn²⁺,Eu³⁺ can be well tuned from yellow to orange and ultimately turned into Eu³⁺ pure red emission by controlling the Eu³⁺ concentration. Moreover, a significantly prolonged Eu³⁺ UC emission lifetime is observed in this system, and it is ascribed to the genetic effect of the sustained resonance energy transfer from Yb³⁺–Mn²⁺ dimers to Eu³⁺. The pump power and temperature dependent UC behaviors further suggest that the phosphor exhibits excellent chromaticity stability. Owing to the long-lived and chromaticity stable UC luminescence, the as-prepared KCdF₃:Yb³⁺,Mn²⁺,Eu³⁺ phosphor may be a highly suitable candidate for lifetime-encoded information encryption, anti-counterfeiting, etc.