Three polymerized small molecule acceptors (PSMAs), namely PY-TP, PY-TPMe2, and PY-TPMe4, were designed and synthesized by employing (bisthiophene)benzene linkers containing various methyl-substituted phenylene groups. All the PSMAs exhibit similar absorption maxima in films as well as LUMO energy levels. However, the increased number of methyl groups on the linkers induces steric hindrance and decreases the coplanarity of the polymer backbones, which, in turn, increases intermolecular π–π stacking distances. When the three acceptors are blended with a classical polymer donor PM6, PY-TPMe4 with a highly twisted backbone has a large π–π stacking distance and excessive phase separation, whereas PY-TP and PY-TPMe2 with moderately twisted backbones demonstrate more compact π–π stacking and suitable phase separation morphology. As a result, PY-TP and PY-TPMe2 exhibit better exciton dissociation and charge transport, leading to much higher photovoltaic performance compared to PY-TPMe4. Particularly, PY-TPMe2 effectively regulates the crystallinity and achieves a more suitable phase separation morphology in the blend films. The optimal PY-TPMe2-based photovoltaic device exhibits the best exciton dissociation and charge transport performance, achieving the highest power conversion efficiency (PCE) of 8.4% among the devices based on the three PSMAs, with a high open-circuit voltage (V_OC) of 0.97 V, a short-circuit current density (J_SC) of 14.74 mA cm⁻² and a fill factor (FF) of 59.65%. These findings provide new insights into the regulation of the molecular packing and photovoltaic performance of polymer acceptors through simple methylation modification on linkers for designing novel PSMA materials.

中文翻译：

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通过简单的甲基化工程调节（比噻吩）苯连接聚合物受体的封装和光伏性能


采用含有各种甲基取代苯基团的（双噻吩）苯接头设计合成了三种聚合小分子受体 （PSMA），即 PY-TP、PY-TPMe2 和 PY-TPMe4。所有 PSMA 在薄膜中都表现出相似的最大吸收率以及 LUMO 能级。然而，接头上甲基数量的增加会诱导空间位阻并降低聚合物骨架的共面性，这反过来又会增加分子间 π-π 堆叠距离。当三个受体与经典聚合物供体 PM6 共混时，具有高度扭曲骨架的 PY-TPMe4 具有较大的 π-π 堆叠距离和过度的相分离，而具有适度扭曲骨架的 PY-TP 和 PY-TPMe2 表现出更紧凑的 π-π 堆叠和合适的相分离形态。因此，PY-TP 和 PY-TPMe2 表现出更好的激子解离和电荷传输，与 PY-TPMe4 相比，光伏性能要高得多。特别是，PY-TPMe2 有效地调节了结晶度，并在共混膜中实现了更合适的相分离形貌。最佳的基于 PY-TPMe2 的光伏器件表现出最佳的激子解离和电荷传输性能，在基于三种 PSMA 的器件中实现了最高的功率转换效率 （PCE），达到 8.4% 的最高功率转换效率 （PCE），具有 0.97 V 的高开路电压 （V_OC），短路电流密度 （J_SC） 为 14.74 mA ^cm-2，填充因子 （FF） 为 59.65%。 这些发现为通过对接头进行简单的甲基化修饰来设计新型 PSMA 材料，为聚合物受体的分子包装和光伏性能的调节提供了新的见解。