Trivalent rare earth Eu3+-doped luminescent materials have been used successfully for illumination and displays due to their narrow emission lines and extreme stability. Extending the excitation band to the UV, near UV and blue region via doping lanthanide ions as a sensitizer is highly desired for white LED application. However, the complex redox reaction and forward/backward energy-transfer pathway between the sensitizer ion and Eu3+ ion in the same lattice of the phosphor host limits the potential of this strategy. Herein, we present the luminescence properties of hierarchical porous composite materials with the formula Tb(C12H8N2)2(NO3)3@Ca0.9Eu0.1MoO4 and report how interfacial energy-transfer enhanced the absorption range of the Eu3+-doped material in the UV region. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images illustrated that the obtained Ca0.9Eu0.1MoO4 had a hierarchical porous structure, and the Tb(C12H8N2)2(NO3)3 was evenly filled inside the holes or the surface. The photoluminescence and decay data indicated the existence of interfacial forward energy transfer from Tb3+ → Eu3+. Furthermore, the thermal stability of the composited Tb(C12H8N2)2(NO3)3 was improved, indicating the potential of the composite materials for application in UV light-emitting diodes.
Halogen vacancies are regarded to play a vital role in photo-induced phase segregation and the resulting switchable emission colors in the soft mixed-halide perovskites ; however, its control strategy via the balanced Pb 0 defects remains a big challenge. The research reports the regulation of synthesis and photochromic behavior via interfacial Eu 3+ /Eu 2+ -Pb 0 /Pb 2+ redox in composites of porous Ca 0.9 Eu 0.1 MoO 4 and nominal mixed-halide perovskite CsPbCl 1.5 Br 1.5 . The composite takes full advantage of Eu 3+ ions with the concerns of its luminescence and variable valences. It provides an additional emission color besides the halide perovskite, manipulates the Pb 0 defects and the resulting Br-rich domain via interfacial redox reaction in the composites. The more contents of surfaced Eu 3+ caused by substituting the unequivalent Ca 2+ ions and the high volume-to-surface ratio of the porous Ca 0.9 Eu 0.1 MoO 4 guarantees the interfacial access for the Eu 3+ and the halides. The research provides some perspectives on the regulation of ionic valence and photoluminescence of halide perovskites with the use of lanthanide ions. The composites may find potential applications in the anti-counterfeiting field.
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