High-performance and scalable large-area organic solar cells enabled by alloy-like composite-induced optimized morphology processed from non-halogenated solvent in air

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• Scalable, eco-friendly OSCs enabled by alloy-like blends of low- and high-crystalline small molecule acceptors. • Ternary system shows strong tolerance to thickness/area variations and excellent stability under light and heat. • Achieved > 69.7% FF and > 14.2% PCE in large-area OSCs (up to 55.0 cm²) with minimal cell-to-module efficiency loss. This study presents a scalable and eco-friendly approach for high-performance organic solar cells (OSCs) by optimizing photoactive morphology with an alloy-like composite structure between small molecule acceptors (SMAs). Processing the photoactive film in ambient conditions using non-halogenated solvents, we address key challenges in efficiency, scalability, stability, and environmental impact for commercially available OSCs. The unique combination of low- and high-crystalline SMAs offers a balanced and refined bulk-heterojunction morphology that enhances charge transfer/transport, reduces recombination/energy losses, and yields high/balanced carrier mobility. The low-crystalline acceptor (Y6-HU) provides flexibility to the molecular arrangement, while the high-crystalline component (BTP-eC9) establishes ordered charge transport pathways. This synergy leads to improved tolerance to photoactive thickness/area variations, enhanced batch-to-batch reproducibility, and outstanding device stability under light and thermal exposure, enabling consistent fill factors over 69.7 % and power conversion efficiencies over 14.2 % across large-area OSCs up to 55.0 cm 2 with minimal cell-to-module efficiency loss. These photovoltaic parameters are among the highest values ever achieved for OSCs fabricated via a spin-coating-free process using non-halogenated solvents. Our strategy achieves high efficiency and stability while ensuring environmental sustainability, advancing OSC technology for scalable, eco-friendly photovoltaic solutions in diverse applications.