Aryane Tofanello

Lead halide perovskites have emerged as promising materials for next‐generation optoelectronic devices due to their outstanding physicochemical properties and low‐cost fabrication. However, widespread application remains limited by pronounced chemical instability under ambient conditions, particularly in the presence of moisture. Traditionally viewed as a primary trigger of degradation, water promotes lattice collapse through hydration, ion migration, and photooxidative pathways. We critically analyze the multifaceted role of water in halide perovskite chemistry, shifting the paradigm from degradation toward controlled functionality. Beyond its detrimental effects, we highlight how controlled exposure to moisture can enhance material quality through water‐assisted synthesis, recrystallization, and defect healing, promoting oriented crystal growth and the formation of stable hybrid and heterostructured architectures. By integrating mechanistic insights with emerging water‐mediated processes, this review outlines new opportunities for water‐controlled synthesis and stability engineering of halide perovskites, enabling robust materials that leverage water as a functional, kinetic, and structural agent, thereby transforming a traditional challenge into a platform for innovation.

Racemic mixtures drive dimensionality and induce broadband emission in lead bromide perovskites. Temperature-dependent optical and structural studies reveal that exciton dynamics are related to octahedral distortions and hydration effects.

Characteristic photon emissions in low-dimensional hybrid perovskites are strongly related to inherent distortions in the crystal lattice. These cooperative distortions, influenced by organic spacers and the confined BX₆ octahedral arrangement, allow for the manipulation and control of the emitted photon energy and its nature. Herein, we observed a complex dynamic where photon emissions at both low and high energies emerge, depending on octahedral distortion and the application of hydrostatic pressure. Our results demonstrated that samples featuring different octahedral sizes and distortions but having a common organic spacer (BA₂MAPb₂Br₇ and BA₂MAPb₂I₇) showed low-energy photon emission attributed to self-trapped excitons (STEs), which can be tuned towards free exciton (FE) states through pressure annealing. Experimental and theoretical results revealed that octahedral distortions in 2D perovskites played a crucial role in controlling emission, disclosing their complex structure and electronic relationship.

Investigation of sodium/indium-based 2D double perovskites with mono- and divalent organic spacers reveals significant optoelectronic impacts in a novel lead-free Dion–Jacobson phase due to octahedral distortions.

Hematite nanoceramics is considered as one of the most promised materials for photoelectrochemical (PEC) water splitting due to its remarkable characteristics such as low band gap, earth abundant composition and stability. In general, the hematite design over fluorine‐doped tin oxide (FTO) glass substrate involve high thermal treatment to promote its surface activation. As consequence, Sn from FTO substrate is commonly found migrating through the hematite layer. This unintentional Sn species diffusion is often associated with improvements on the photoelectrochemical response. The role played by Sn migrating from FTO against intentionally incorporated during the synthesis process into hematite to boost its performance remain unclear. In this perspective, the complexity of these matters was discussed to reveal the contribution and limiting aspects of each effect on the hematite manufacture. Indeed, a deep comprehension and latest advances on Sn diffusion and incorporation role on hematite led us to find synergistic characteristics between them, indicating economically viable alternatives to design active hematite nanoceramics. Regardless of its morphology, the key direction is based on external modifications which reduce energetic barriers on interfaces to favor electron carrier dynamics.