Advances in <scp>2D</scp> / <scp>3D</scp> perovskite heterostructures: Toward commercially viable perovskite solar cells

Abstract Perovskite solar cells (PSCs) have achieved power conversion efficiencies exceeding 26%, yet their commercialization remains limited, mainly due to instability caused by defect‐mediated nonradiative recombination, ion migration, and environmental degradation of the three‐dimensional (3D) perovskite. Introducing two‐dimensional (2D) perovskite layers at the top, bottom, or both interfaces of the 3D perovskite has emerged as an effective strategy to passivate defects, optimize band alignment, suppress ion migration, and enhance moisture and thermal stability. This mini‐review summarizes recent progress in mixed‐dimensional 2D–3D perovskite heterostructures, highlighting different approaches, including ligand design, phase‐pure 2D growth, and solvent engineering, that lead to high‐efficiency and stable PSCs. Finally, the review outlines remaining challenges and future directions, pointing toward mixed‐dimensional perovskite architectures as a promising route to commercialize PSC technology.