Regulating synthesis and photochromic behavior via interfacial Eu3+/Eu2+-Pb0/Pb2+ redox of the CsPbCl1.5Br1.5@ Ca0.9Eu0.1MoO4 porous composites

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.