Exploiting Dimensionality in Hybrid Metal Halides: Design Strategies, Structure–Property Relationships, Optoelectronic Applications, and Future Perspectives

Low-dimensional perovskite-type hybrid metal halides (HMHs) have become a research hotspot due to their excellent photoelectric properties and structural tunability. Compared with traditional three-dimensional perovskite-type HMHs, low-dimensional materials exhibit many outstanding advantages, including wide-range tunability of bandgaps, enhancement of exciton binding energy, ultrahigh photoluminescence quantum yield (PLQY), and improvement of environmental stability. However, the related research on low-dimensional HMHs still lacks systematic organization, there is no unified standard for dimension determination and design criteria, and the dimension control and performance analysis are not comprehensive and specific enough. Therefore, this article takes the connection mode of MX₆ octahedra as the main line, constructs a systematic structural classification framework covering three-dimensional (3D), two-dimensional (2D), one-dimensional (1D), and zero-dimensional (0D) structures, systematically reviews dimension engineering strategies such as organic cation engineering, metal cation regulation, external field stimulation modulation, and synthesis route optimization, and extracts the structure–activity relationships dominated by dimension and corresponding application scenarios. This research aims to establish a unified conceptual framework and provide methodological guidance, to support the further development of low-dimensional HMHs.