Simultaneous Multicolor Emission of Down-Shifting and Up-Conversion in Er3+, Yb3+-Codoped Cs2NaScCl6 Double Perovskites

Lanthanide ion-doped metal halides are a promising class of fluorescent materials. In this paper, we investigated the optical properties and photophysical mechanism of Er3+, Yb3+-doped Cs2NaScCl6 phosphor. It was demonstrated that in both up-conversion (UC) and down-shifting emission modes, the increase of Yb3+ concentration resulted in enhancement of the 4F9/2 → 4I15/2 emission of Er3+ in Cs2NaScCl6. In particular, UC emission gradually shifts from green to yellow with the enhancement of the excitation power density observed in Yb3+-rich systems. The complex cross-relaxation behavior between Yb3+ and Er3+ results in these phenomena. New paradigms are provided for the development of multimodal and dynamic fluorescent anticounterfeiting materials.