Bonding Mechanisms Underpinning Structural and Electronic Properties of Halide Perovskites

Halide perovskites have emerged as a versatile class of optoelectronic materials, exhibiting outstanding performance across a broad spectrum of applications, including photovoltaics, light-emitting devices, non-classical light sources, and radiation detectors. On the fundamental side, the nature of chemical bonding in halide perovskites plays a crucial role in determining their structural and (opto)electronic properties, chemical stability, and formability. For instance, their electronic bandgap is highly sensitive to octahedral tilting as well as to lattice expansion or contraction, due to changes in the orbital overlap. In fact, one of the most intriguing features of halide perovskites is their dynamic structural behavior rooted in the flexibility of the BX6 octahedra framework, which underpins complex interactions between charge carriers and the lattice. These materials exhibit pronounced structural softness and anharmonicity, as indicated by their low thermal conductivity and high thermal expansion coefficients. These features significantly influence charge transport and thermolectric properties, making halide perovskites promising candidates for various applications. In this context, this review aims to provide readers with a comprehensive overview of recent advances in the detailed atomic-scale characterization of halide perovskites, combining experimental structural chemistry and computational techniques, an essential step toward the rational design of novel materials with tailored optoelectronic properties for next-generation technologies. It examines the atomic structure and dynamics of these materials, emphasizing how chemical bonding within the inorganic framework and interactions with organic moieties in hybrid and layered systems govern their structural behavior, ultimately influencing their optoelectronic performance.