Toward Stable and Efficient Perovskite Solar Cells: Unlocking the Potential of Porous PbI₂ Scaffolds via Two-Step...

The two-step sequential deposition method for perovskite solar cells (PSCs) is often limited by the dense PbI₂ film morphology, leading to incomplete conversion, residual PbI₂, and high defect density. This review consolidates research showing that engineering a porous PbI₂ architecture is a universal and transformative solution. We categorize the key strategies: (1) Solvent Engineering: Using solvent extraction, vapor treatment, or anti-solvent methods to create rapid nanoporosity; (2) Molecular Additives: Lewis bases or volatile amines that coordinate with Pb²⁺, disrupting crystallization and forming porous scaffolds; (3) Ionic Liquids and Salts: Multi-functional agents templating porosity while passivating defects and boosting stability; (4) Sacrificial Agents and Frameworks: Pore-forming compounds or MOFs/COFs that provide predefined porous structures; (5) Interfacial Engineering: Substrate modifications or low-dimensional seeds guiding favorable PbI₂ porosity. A porous PbI₂ scaffold enhances organic salt diffusion, ensuring complete conversion to high-quality perovskite films with larger grains, improved crystallinity, and lower trap densities. This consistently yields PSCs with efficiencies >25%-26% and outstanding stability, often retaining >90% performance after thousands of hours. Controlling PbI₂ morphology thus offers a scalable route to enhance perovskite photovoltaic performance and commercial viability.