A Quasi‐n‐i‐p Architecture Realized by Sequential Lamination Delivers 20.58% Efficiency in Inverted Organic Solar Cells

Inverted organic solar cells (OSCs) are promising for their enhanced operational stability; however, their power conversion efficiencies (PCEs) have lagged those of conventional devices, largely due to interfacial losses at the active layer/metal‐oxide interface. Here, we develop a sequential lamination strategy to construct a quasi‐n‐i‐p active layer comprising an acceptor‐rich layer, a bulk heterojunction (BHJ) core, and a donor‐rich layer. This vertically engineered architecture establishes cascade energy‐level alignment and preserves interfacial integrity, thereby facilitating efficient charge extraction and suppressing recombination losses. As a result, the optimal device achieves a PCE of 20.58%, with a certified efficiency of 20.07%, placing it among the highest reported for single‐junction inverted OSCs. This architecture was successfully fabricated with different donor‐rich layers, BHJ cores, and acceptor‐rich layers, demonstrating broader material applicability across multiple material combinations. Interfacial adhesion and vertical compositional control improve electrical continuity, enhance charge generation and transport, and reduce trap‐assisted and bimolecular recombination, leading to higher open‐circuit voltage, short‐circuit current density, and fill factor. This work provides a scalable route to active‐layer engineering in inverted OSCs and offers a general strategy for high‐performance organic photovoltaic fabrication.