Chlorination-controlled aggregation and film-formation kinetics enabling high-efficiency organic solar cells with low-cost linear conjugated polymers

The pursuit of simple yet high-performance materials is important for advancing organic photovoltaics, though structurally simple polymer donors typically underperform. This study reveals precise control over polymer aggregation and donor-acceptor compatibility is key to optimizing active layer morphology. We design three linear conjugated polymers with systematically chlorinated backbones to finely modulate aggregation tendency and surface tension. This strategy concurrently regulates film-formation kinetics and donor-acceptor compatibility. PTTz-Cl50 exhibits ideal aggregation and optimal compatibility with BTP-eC9, enabling sequential deposition that forms a bicontinuous interpenetrating network with appropriate domain size and marked phase purity. This microstructure provides sufficient interfacial area for exciton dissociation while retaining high-purity charge transport pathways. Consequently, the device demonstrates rapid exciton dissociation, efficient charge transport, and suppressed recombination, enhancing both short-circuit current and fill factor. This yield a high power conversion efficiency of 20.42% for linear conjugated polymers, underscoring the promise of low-cost materials for efficient devices. Yin et al. report linear conjugated polymer donors with chlorinated backbone for modulating polymer aggregation and surface tension, and optimised compatibility with norfullerene acceptors. By using binary blends, a 20.42% efficiency is achieved for organic solar cells.