A Giant Acceptor with a Novel Oxygenated Linker Modulates Molecular Crystallization Kinetics for High-Efficiency Non-Halogenated-Processed Organic Solar Cells.

Abstract

The use of low-boiling-point halogenated solvents is common in lab-scale organic solar cell (OSC) fabrication to achieve high power conversion efficiencies (PCEs), but their high volatility hinders large-scale fabrication. High-boiling-point, non-halogenated solvents are adopted as alternatives, but they often result in significant efficiency losses due to inferior morphology. In this work, toluene is adopted, enabling scalable production without any post-treatment. Two giant guest acceptors, featuring distinct oxygenated side chains, are introduced to modulate pre-aggregation in solution and crystallization kinetics within the PM6:BTP-eC9 blend. The incorporation of giant acceptors effectively inhibits rapid acceptor aggregation and promotes smaller phase separation. Moreover, G-1O with a shorter oxygenated side chain yields more homogeneous phase separation, whereas G-3O with a longer side chain leads to uneven separation. Therefore, the G-1O-based ternary device achieves an outstanding PCE of 20.02%. Notably, a high PCE of 16.97% is also obtained in a large-area module (15.6 cm², without dead zone). These findings highlight the critical role of oxygenated side-chain engineering in guest molecules for tuning crystallization kinetics under toluene processing.