Bulk Synthesis of Phase‐Pure Ruddlesden‐Popper Phase Perovskites via Iodide‐Mediated Mechanochemistry

Ruddlesden-Popper (RP) perovskites offer exceptional optoelectronic properties but face persistent challenges in achieving simultaneous control over phase purity, processability, and scalable synthesis. Here, we overcome this limitation through iodide-mediated liquid-assisted grinding (LAG), enabling gram-scale synthesis of phase-pure quantum-well perovskites (n = 1-4) with >98% phase fidelity. By introducing hydroiodic acid (HI) during mechanochemical milling, we achieve kinetic acceleration via liquid-phase ionic incorporation, bypassing solid-state diffusion barriers to drive stoichiometry-directed assembly into monophase crystals (0.1-5 µm). The resulting powders resolve scalability-processability constraints by enabling spark plasma sintering consolidation into centimeter-scale bulk monoliths with improved crystallographic orientation, and facilitating conformal coatings on flexible/curved substrates via screen printing. Critically, these processable forms support heterogeneous integration with 3D perovskites to create functional heterostructures. This work establishes a platform for deterministic quantum-well design, unlocking scalable production and integration of 2D perovskites for advanced optoelectronics.