Among perovskites, the research on cesium lead iodides (CsPbI₃) has attracted a large research community, owing to their all-inorganic nature and promising solar cell performance. Typically, the CsPbI₃ solar cell devices are prepared at various heterojunctions, and working at fluctuating temperatures raises questions on the material stability-related performance of such devices. The fundamental studies reveal that their poor stability is due to a lower side deviation from Goldschmidt’s tolerance factor, causing weak chemical interactions within the crystal lattice. In the case of organic–inorganic hybrid perovskites, where their stability is related to the inherent chemical nature of the organic cations, which cannot be manipulated to improve the stability drastically whereas the stability of CsPbI₃ is related to surface and lattice engineering. Thus, the challenges posed by CsPbI₃ could be overcome by engineering the surface and inside the CsPbI₃ crystal lattice. A few solutions have been proposed, including controlled crystal sizes, surface modifications, and lattice engineering. Various research groups have been working on these aspects and had accumulated a rich understanding of these materials. In this review, at first, we survey the fundamental aspects of CsPbI₃ polymorphs structure, highlighting the superiority of CsPbI₃ over other halide systems, stability, the factors (temperature, polarity, and size influence) leading to their phase transformations, and electronic band structure along with the important property of the defect tolerance nature. Fortunately, the factors stabilizing the most effective phases are achieved through a size reduction and the efficient surface passivation on the delicate CsPbI₃ nanocrystal surfaces. In the following section, we have provided the up-to-date surface passivating methods to suppress the non-radiative process for near-unity photoluminescence quantum yield, while maintaining their optically active phases, especially through molecular links (ligands, polymers, zwitterions, polymers) and inorganic halides. We have also provided recent advances to the efficient synthetic protocols for optically active CsPbI₃ NC phases to use readily for solar cell applications. The nanocrystal purification techniques are challenging and had a significant effect on the device performances. In part, we summarized the CsPbI₃-related solar cell device performances with respect to the device fabrication methods. At the end, we provide a brief outlook on the view of surface and lattice engineering in CsPbI₃ NCs for advancing the enhanced stability which is crucial for superior optical and light applications.

NiFe‐based MIL‐55 metal‐organic frameworks (MOFs) face challenges in achieving atomically precise composition and reliable methods for uniform growth. This study addresses these challenges by applying a slow evaporation crystallization technique to crude colloidal MIL‐55 products from hydrothermal synthesis, resulting in highly uniform, hexagonal pyramid‐shaped NiFe‐MIL‐55 nanorods (NRs). In contrast, isolating MIL‐55 through antisolvent precipitation leads to irregular shapes, highlighting the critical role of the crystallization method. This shape control enables single‐particle analysis, revealing tunable atomic compositions ranging from Ni ₁ Fe ₉ to Ni ₉ Fe ₁ by adjusting the Ni ²⁺ /Fe ³⁺ precursor ratios. A volcano‐type morphology plot illustrates the role of the Ni‐BDC framework in shape control, where Ni ₄ Fe ₆ to Ni ₈ Fe ₂ compositions produce uniform NRs, whereas others yield mixed or irregular morphologies. The electrocatalytic oxygen evolution reaction (OER) and supercapacitor performances of these NRs were evaluated, with Ni ₇ Fe ₃ ‐MIL‐55 showing the best OER performance, including a low overpotential of 230 mV at 10 mA cm ⁻² and a Tafel slope of 64 mV dec ⁻¹ . It also demonstrates excellent stability, retaining 82% of its OER activity over 50 h, as well as superior supercapacitor performance (571 F g ⁻¹ at 1 A g ⁻¹ ), making it a promising dual‐function material. Density functional theory (DFT) calculations reveal that Ni ₇ Fe ₃ has the lowest limiting potential (0.52 V) compared to its single‐metal counterparts, explaining its enhanced OER activity. This work provides a strategy for atomically precise MOF nanostructure design, offering valuable insights into electrocatalytic behavior and guiding the development of materials for renewable‐energy technologies.