Lanthanide double perovskites (Ln-DPs) offer tunable emission and low toxicity, yet their weak crystal fields often fail to support efficient upconversion luminescence of lanthanide ions, limiting multimodal applications. While conventional dual-mode luminescence relies on complex core-shell architectures to mitigate cross-relaxation, we demonstrate here, in contrast, highly efficient dual-mode (upconversion and downshifting) emission from a simple bilayer heterostructure. An optimized thermal injection approach was employed to synthesize the heterostructure nanocomposites of Ln-DPs. And the incorporation of NaLnF4 not only enhanced the intrinsic luminescence and structural stability of the Ln-DPs via surface passivation, but also leveraged ion migration to provide an optimal crystal field for Er3+ ions, enabling tunable upconversion luminescence through its self-absorption. Subsequently, by regulating lanthanide ion concentration and spatial distribution, the red emission intensity of Er3+ ions was further improved by a factor of 13.23. This design offers a simple yet powerful strategy for achieving high-performance Ln-DPs light-emitting devices, highlighting their potential application in advanced optical coding and information encryption.
Guan et al. (2026) studied this question.