Controlled Solution Flow via Patterned Meniscus Assist for Elongated Exciton Diffusion Length to Approaching 20% Efficiency in Pseudo‐Planar Heterojunction Organic Solar Cells

Precisely controlling the ideal vertical phase morphology of blade-coated pseudo-planar heterojunction (PPHJ) organic photovoltaics presents a key challenge due to Marangoni flow and coffee-ring effect, which further limits large-area film uniformity and shortens exciton diffusion length. Here, the patterned meniscus assist (PMA) strategy is used to stretch polymer chains and construct regular micropatterns to facilitate donor/acceptor inter-penetration, resulting in a high-performance printable PPHJ device with extended exciton diffusion length (from ≈45 to ≈56 nm). More importantly, micropatterns can mitigate Marangoni flow and promote film uniformity by enhancing solution flow. Consequently, the PPHJ device via PMA strategy exhibits one of the highest power conversion efficiencies (PCE) of 19.91% (certified as 19.63%) for the D18/BO-4Cl:L8-BO ternary system. Furthermore, the enlarged-area (1 and 16.94 cm²) devices show competitive PCEs of 18.90%/17.05% with one of the minimum PCE losses (5.07%/14.36%) during area expansion. This PMA strategy provides a feasible guiding avenue for realizing ideal active layer morphology to obtain large-scale, high-efficiency PPHJ devices.