UC Berkeley

Metal halide perovskites, a class of semiconducting materials with remarkable optoelectronic properties, have attracted considerable attention in recent years. This dissertation delves into innovative design and synthesis approaches, as well as structural transformations and applications of halide perovskites, with a focus on the fundamental properties of the metal halide ion octahedron [MX6]n– (M = metal cation, X = halide anion) as the primary building block and functional unit. By examining the assembly, connection, and interaction of these octahedra, this research aims to establish a solid foundation for the future development and application of halide perovskites.Chapter 1 provides a comprehensive overview of halide perovskites, covering their fundamentals, structural chemistry, stimulus response, and applications, with particular emphasis on the metal halide octahedron as the key building block and functional unit. In Chapter 2, we propose a new design principle for halide perovskite structures based on ionic octahedron networks (IONs) and report the first experimental synthesis of a novel halide perovskite, Cs8Au3.5In1.5Cl23, which adopts an ABO3-type ION. Chapter 3 examines the stimulus-responsive behavior of metal halide perovskites, using Cs3Bi2Br9 as a model compound. By employing in situ characterization techniques, we identify two distinct distortion classes of [BiBr6]3– octahedra and analyze the changes in exciton emissions in relation to the octahedral distortion. In Chapter 4, we utilize our understanding of [MX6]n– octahedra to establish the electronic band structure and photoexcitation model of molecule-like halide perovskite Cs2TeBr6. We demonstrate that different LED wavelengths can generate holes in various valence bands and differentially activate benzyl alcohol molecules. Lastly, Chapter 5 summarizes the research findings and provides insights into future directions for halide perovskite studies, emphasizing the significance of understanding the metal halide ion octahedron.