Efficient organic solar cells (OSCs) often use combination of polymer donor and small molecule acceptor. Herein we demonstrate efficient and thermally stable OSCs with combination of small molecule donor and polymer acceptor, which is expected to expand the research field of OSCs. Typical small molecule donors show strong intermolecular interactions and high crystallinity, and consequently do not match polymer acceptors because of large-size phase separation. We develop a small molecule donor with suppressed π-π stacking between molecular backbones by introducing large steric hindrance. As the result, the OSC exhibits small-size phase separation in the active layer and shows a power conversion efficiency of 8.0%. Moreover, this OSC exhibits much improved thermal stability, i.e. maintaining 89% of its initial efficiency after thermal annealing the active layer at 180 °C for 7 days. These results indicate a different kind of efficient and stable OSCs.

高效有机太阳能电池（OSC）通常使用聚合物供体和小分子受体的组合。在此，我们展示了小分子供体和聚合物受体相结合的高效且热稳定的OSC，这有望扩大OSC的研究领域。典型的小分子供体表现出强烈的分子间相互作用和高结晶度，因此由于大尺寸的相分离而与聚合物受体不匹配。我们通过引入大的空间位阻开发了一种小分子供体，其分子主链之间的 π-π 堆积受到抑制。结果，OSC在有源层中表现出小尺寸的相分离，并且功率转换效率为8.0%。此外，该OSC表现出大大改善的热稳定性，即在180°C对有源层进行热退火7天后仍保持其初始效率的89%。这些结果表明了一种不同类型的高效且稳定的 OSC。