Orthogonal Solvent-Assisted Sequential Deposition for High-Performance Organic Solar Cells: Synergistic Enhancement of Efficiency and Mechanical Properties

Sequential deposition has emerged as an effective strategy to modulate the morphology of the active layer and enhance the power conversion efficiencies (PCEs) of organic solar cells (OSCs). However, conventional sequential methods often employ nonorthogonal solvents for the upper layer, leading to excessive donor–acceptor interpenetration, which compromises the mechanical properties and limits the flexibility of the active layers. Herein, we report a small-molecule/polymer blend acceptor strategy to construct a well-controlled P-i-N device architecture using orthogonal solvents to optimize the PCE and mechanical robustness simultaneously. The P-i-N devices exhibit a strong dependence on the upper-layer processing solvent, achieving a remarkable PCE of 18.67% and a crack-onset strain of 15.48%. In situ morphological and device analyses demonstrate that the enhanced crystallinity, more face-on orientation, and purer phases introduced by N2200 are beneficial for improving charge transport and decreasing bimolecular recombination in OSCs. Furthermore, the incorporation of polymer N2200 results in stable blend film nanostructures, thus improving the mechanical properties of the devices. These structural optimizations collectively suppress bimolecular recombination while enhancing both photovoltaic efficiency and mechanical robustness. This work provides a viable pathway toward high-performance and flexible OSCs for practical applications.