Stabilizing RbPbBr ₃ Perovskite Nanocrystals through Cs ⁺ Substitution

ABX ₃ -type halide perovskite nanocrystals (NCs) have been a hot topic recently due to their fascinating optoelectronic properties. It has been demonstrated that A-site ions have an impact on their photophysical and chemical properties, such as the optical band gap and chemical stability. The pursuit of halide perovskite materials with diverse A-site species would deepen the understanding of the structure–property relationship of the perovskite family. In this work we have attempted to synthesize rubidium-based perovskite NCs. We have discovered that the partial substitution of Rb ⁺ by Cs ⁺ help to stabilize the orthorhombic RbPbBr ₃ NCs at low temperature, which otherwise can only be obtained at high temperature. The inclusion of Cs ⁺ into the RbPbBr ₃ lattice results in highly photoluminescent Rb _1−x Cs _x PbBr ₃ NCs. With increasing amounts of Cs ⁺ , the band gaps of the Rb _1−x Cs _x PbBr ₃ NCs decrease, leading to a redshift of the photoluminescence peak. Also, the Rb _1−x Cs _x PbBr ₃ NCs (x=0.4) show good stability under ambient conditions. This work demonstrates the high structural flexibility and tunability of halide perovskite materials through an A-site cation substitution strategy and sheds light on the optimization of perovskite materials for application in high-performance optoelectronic devices.