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

Abstract

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 Pb0 defects remains a big challenge. The research reports the regulation of synthesis and photochromic behavior via interfacial Eu3+/Eu2+-Pb0/Pb2+ redox in composites of porous Ca0.9Eu0.1MoO4 and nominal mixed-halide perovskite CsPbCl1.5Br1.5. The composite takes full advantage of Eu3+ ions with the concerns of its luminescence and variable valences. It provides an additional emission color besides the halide perovskite, manipulates the Pb0 defects and the resulting Br-rich domain via interfacial redox reaction in the composites. The more contents of surfaced Eu3+ caused by substituting the unequivalent Ca2+ ions and the high volume-to-surface ratio of the porous Ca0.9Eu0.1MoO4 guarantees the interfacial access for the Eu3+ 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.