Weak-Interaction-Driven Self-Positioning for Multi-Site Modification in Perovskite Solar Cells

Interfacial engineering is a key strategy for suppressing non-radiative recombination and optimizing energy-level alignment in perovskite solar cells, which must be implemented at multiple sites for the state-of-the-art devices to further approach their theoretical efficiency limit. However, conventional modification methods typically rely on depositing additional ultrathin layers at specific interfaces, complicating the manufacturing procedure and requiring precise control to achieve multi-site modification. Here, a weak-interaction-driven self-positioning strategy is proposed to realize multi-site modification without any additional deposition step. Metal phthalocyanine-based modifiers with tunable coordination affinities are investigated, and spatially selective self-positioning of ligands and alkali metal ions is revealed for Na₂Pc and Li₂Pc-modified films. During film formation, these weakly coordinated complexes dissociate, leading to spontaneous migration of alkali metal ions toward the SnO₂/perovskite interface, accompanied by preferential enrichment of ligands at the upper surface. The resulting synergistic multi-site modification significantly enhances the built-in electric field and suppresses non-radiative recombination. Consequently, the Li₂Pc-modified device (0.1 cm²) reaches an open-circuit voltage (V_OC) of 1.204 V and a power conversion efficiency (PCE) of 25.60%, corresponding to over 95% of the theoretical V_OC limit. A high V_OC of 1.177 V is reached for 1.0 cm² devices, offering a clear competitive advantage and strong potential for scalable applications.