A morphology controller for high-efficiency bulk-heterojunction polymer solar cells

Controlling the morphology in bulk-heterojunction solar cells is the preferred and most effective way to achieve high efficiency. To control the morphology, we synthesized a novel hydrophobic end-functionalized P3HT to induce hydrophilic-hydrophobic repulsive interactions in the boundary between the relatively hydrophilic PCBM and the relatively hydrophobic P3HT. The introduction of hydrophobic end-functionalized P3HT (F-P3HT) leads to larger PCBM clusters, while maintaining the crystallinity of P3HT due to repulsive interactions. F-P3HT thus provides a maximized continuous interfacial area between the donor and the acceptor as well as bi-continuous networks of donor and acceptor domains, resulting in better percolation pathways for charge transport.