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

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.