The flexibility and stability of organic solar cells (OSCs) are becoming hotspot research due to their practical applications. Molecular arrangement and network morphology of the active layer are important factors affecting the flexibility and stability of OSCs. Here, two polymer donors (PBB1-Cl and PBB2-Cl) with different side chains were investigated as the third component to finely regulate morphology and molecular accumulation of the active layer to improve the performance of OSCs. Both third components show complementary absorption spectra and good compatibility. The good planarity of PBB1-Cl and PBB2-Cl significantly increases intermolecular overlap to promote the charge transfer in the active layer. In addition, the steric hindrance of the one-dimensional side chain of PBB1-Cl enhanced the intermolecular close packing and entanglement of the active layer. As a result, the tensile endurance of PM6:PBB1-Cl:Y6-BO-4Cl ternary blend film reached 4.6 times (26.86%) of the PM6:Y6-BO-4Cl binary blend film. Furthermore, the power conversion efficiency (PCE) increased from 15.83% for PM6:Y6-BO-4Cl based binary OSCs to 17.36% for PBB1-Cl based rigid ternary OSCs, and the flexible OSCs increased from 13.44% to 14.96%, respectively. 17.36% efficiency of PBB1-Cl based ternary OSCs is the highest value in OSCs with elongation at the break of active layer exceeding 25% so far. Further, the PCEs of PBB1-Cl-based flexible ternary OSCs still remain above 74% within 500 cycles of bending with a diameter of 10 mm or annealing at 100 °C for 24 hours, which is mainly attributed to the smaller surface energy difference between PBB1-Cl-based ternary blend film and transport layers, higher glass transition temperature and larger elongation at break of the active layer. All results suggest that enhancing intermolecular overlapping fasten packing in the active layer has great potential in improving the photovoltaic performance, mechanical and thermal stability of OSCs.

中文翻译：

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重叠紧固包装可实现具有超拉伸性的高效双供体三元有机太阳能电池

有机太阳能电池 (OSC) 的灵活性和稳定性因其实际应用而成为研究热点。活性层的分子排列和网络形态是影响 OSCs 灵活性和稳定性的重要因素。在这里，研究了具有不同侧链的两种聚合物供体（PBB1-Cl 和 PBB2-Cl）作为第三种成分，以精细调节活性层的形态和分子积累，以提高 OSC 的性能。两种第三组分都显示出互补的吸收光谱和良好的兼容性。PBB1-Cl 和 PBB2-Cl 的良好平面性显着增加了分子间重叠，以促进活性层中的电荷转移。此外，PBB1-Cl 一维侧链的空间位阻增强了活性层的分子间紧密堆积和缠结。结果，PM6:PBB1-Cl:Y6-BO-4Cl三元共混薄膜的拉伸强度达到了PM6:Y6-BO-4Cl二元共混薄膜的4.6倍（26.86%）。此外，基于 PM6:Y6-BO-4Cl 的二元 OSCs 的功率转换效率 (PCE) 从 15.83% 增加到基于 PBB1-Cl 的刚性三元 OSCs 的 17.36%，柔性 OSCs 分别从 13.44% 增加到 14.96%。迄今为止，基于 PBB1-Cl 的三元 OSC 的效率为 17.36%，是迄今为止活性层断裂伸长率超过 25% 的 OSC 中的最高值。此外，基于 PBB1-Cl 的柔性三元 OSCs 在直径为 10 mm 的弯曲或在 100°C 下退火 24 小时的 500 次循环内的 PCE 仍保持在 74% 以上，这主要归因于基于PBB1-Cl的三元共混膜与传输层之间的表面能差异较小，活性层的玻璃化转变温度较高和断裂伸长率较大。所有结果表明，增强活性层中的分子间重叠紧固堆积在改善 OSC 的光伏性能、机械和热稳定性方面具有巨大潜力。