Metal halide perovskite photovoltaics have emerged as promising next-generation solar technologies owing to their high efficiency and compatibility with low-temperature manufacturing. Although small-area perovskite solar cells have achieved certified efficiencies around 28%, scalable fabrication of large-area perovskite films and modules remains a major challenge for commercialization. During scale-up, film formation becomes highly sensitive to coupled transport and solidification processes, including fluid flow, solvent evaporation, vapor transport, supersaturation evolution, nucleation, crystal growth, and phase conversion. These processes generate spatiotemporal heterogeneities that cause nonuniform crystallization, defect formation, and module-level performance losses. In this Review, we establish a crystallization-centered framework for understanding large-area perovskite film fabrication across both solution-based and vapor-based deposition routes. Solution processing methods are discussed from the perspectives of wet-film hydrodynamics and solvent-mediated crystallization, while vapor-based routes are analyzed in terms of precursor transport, surface reaction kinetics, and non-equilibrium growth. Previous studies are further used to relate precursor transport and perovskite crystallization control to film uniformity, device performance, and operational stability. Finally, we discuss emerging strategies for crystallization control and scalable manufacturing toward reliable, high-throughput perovskite photovoltaic modules.

Wide-bandgap (WBG) perovskites are one of the most promising semiconducting materials for high-efficiency tandem solar cells and emerging applications such as indoor photovoltaics and building-integrated photovoltaics. However, mixed-halide WBG perovskites suffer from photo-induced phase segregation, which induces bandgap inhomogeneity, enhances non-radiative recombination, and limits device stability. Here, we present a concise and integrated understanding of phase segregation by linking fundamental mechanisms with experimental characterization. We analyze the interplay among thermodynamic instability, strain-coupled carrier-lattice interactions, and electric-field-driven ion migration, and summarize key techniques for probing phase segregation across multiple length scales. Building on this mechanistic analysis, we review state-of-the-art strategies for suppressing phase segregation, including composition design, crystallization control, interface/passivation engineering, ion-migration regulation, strain modulation, and redox-mediated self-healing approaches. Finally, we outline key challenges and future directions toward achieving intrinsically stable, high-efficiency WBG perovskite solar cells. This review provides both fundamental insights and practical guidance for overcoming one of the most critical barriers to the deployment of WBG perovskite photovoltaics.

Cl-based salts are magical additives to control the perovskite crystallization and enhance film morphology. Especially for the I/Br halide wide-bandgap (WBG) perovskites, alloying Cl to form triple halide perovskites can effectively enhance their optoelectronic characteristics. However, the alloying mechanism of Cl into the I/Br-based perovskite lattice remains unclear. Here, we conduct a systematic in-situ photoluminescence (PL) exploration on the crystallization processes of I/Br-based WBG with Cl-based additives including MACl and PbCl₂. The results reveal that only the Cl from PbCl₂ is easy to incorporate into the I/Br-based perovskite lattice structure at the initial stage of perovskite nucleation. However, PbCl₂ incorporation results in the precipitation of excess PbI₂, which leads to unfavorable charge transport and decreased photostability. With co-incorporation of MACl and CsCl, the transition of crystal orientation during the annealing process is effectively regulated, significantly eliminating the accumulation of excess PbI₂. This improvement enhances phase homogeneity and reduces defect density. Consequently, the optimized WBG perovskite solar cell achieves a high efficiency of 21.58%, which is the highest value for 1.68 eV perovskite with bromine content lower than 10%. In addition, the operational stability is significantly enhanced, along with ameliorated burn-in aging behavior.