Abstract
<jats:p> Realizing multilayer stacks analogous to classical semiconductors with precise control over chemistry, composition, thickness, orientation, and epitaxy using solution-processing has remained a long-standing bottleneck. Here, we present a novel scalable solution-based strategy for the deterministic deposition of any perovskite layer onto an existing perovskite film, enabling multilayer perovskite heterostructures with comparable control. Our approach dissolves pre-synthesized perovskite crystals or precursor salts in a dissolving solvent, followed by dispersion into a miscible carrier solvent to form a metastable colloidal system that can be deposited without disturbing the underlying layer. This universal process enables architectures including 3D-on-3D, 2D|3D, 3D|2D, and more complex multilayers, while independently controlling composition, thickness, orientation, and interfaces. We further show that lattice parameter matching enables orientation control through solution-phase epitaxy. Integrating a formamidinium-rich 3D|2D stack (FA <jats:sub>0.9</jats:sub> Cs <jats:sub>0.1</jats:sub> PbI <jats:sub>3</jats:sub> |(3AMP)FA <jats:sub>2</jats:sub> Pb <jats:sub>3</jats:sub> I <jats:sub>10</jats:sub> ) into p-i-n solar cells increases efficiency from 24.2% to 26.0%, maintained for 2D layer thicknesses up to 80 nm, establishing a versatile platform for scalable semiconductor heterostructures. </jats:p>