Tunable CsPbBr3/Cs4PbBr6 phase transformation and their optical spectroscopic properties

Abstract

As a novel type of promising materials, metal halide perovskites are a rising star in the field of optoelectronics. On this basis, a new frontier of zero-dimensional perovskite-related Cs₄PbBr₆ with bright green emission and high stability has attracted an enormous amount of attention, even though its photoluminescence still requires to clarification. Herein, the controllable phase transformation between three-dimensional CsPbBr₃ and zero-dimensional Cs₄PbBr₆ is easily achieved in a facile ligand-assisted supersaturated recrystallization synthesis procedure via tuning the amount of surfactants, and their unique optical properties are investigated and compared in detail. Both Cs₄PbBr₆ and CsPbBr₃ produce remarkably intense green luminescence with quantum yields up to 45% and 80%, respectively; however, significantly different emitting behaviors are observed. The fluorescence lifetime of Cs₄PbBr₆ is much longer than that of CsPbBr₃, and photo-blinking is easily detected in the Cs₄PbBr₆ product, proving that the zero-dimensional Cs₄PbBr₆ is indeed a highly luminescent perovskite-related material. Additionally, for the first time, tunable emissions over the visible-light spectral region are demonstrated to be achievable via halogen composition modulations in the Cs₄PbX₆ (X = Cl, Br, I) samples. Our study brings a simple method for the phase control of CsPbBr₃/Cs₄PbBr₆ and demonstrates the intrinsic luminescence nature of the zero-dimensional perovskite-related Cs₄PbX₆ products.