Although isoindigo (IID)-based polymers can realize high charge mobility, these materials are currently confined to fullerene-based organic solar cells (OSCs). Herein, we designed a pair of alternative D-π-A type copolymers, PE71 and PE72, to expand the application in non-fullerene OSCs, where benzo[1,2-b:4,5-b′]thiophene (BDT), thieno[3,2-b]thiophene (TT) and IID units were used as D, A and π-bridge, respectively. The aim of optimizing the length of alkyl chains on TT bridge is to ensure polymer solubility, crystallinity as well as miscibility with acceptor molecules. We find that PE71 and PE72 exhibit similar optical and electronic properties, but PE71 with shorter hexyl chain tends to aggregate into fiber-like structure. In the end, Y6 is selected as the electron acceptor because of suitable energy levels and complementary absorption spectrum. Finally, PE71:Y6 device realizes a power conversion efficiency (PCE) of 12.03%, which is obviously higher than that of PE72:Y6 device (9.74%) and is also the highest value for IID-based photovoltaic polymers. The charge transport, molecular aggregation, film morphology and energy loss analysis were systematically investigated. The improved photovoltaic performance of PE71:Y6 mainly originates from the better interpenetrating network structure toward facilitating exciton seperation and free charge carrier transportation. Our results indicate that IID-based D-π-A polymers can also be utilized in non-fullerene OSCs and the alkyl chains on the thieno [3,2-b]thiophene π-bridge have a vital effect on the photovoltaic performance.

尽管基于异靛蓝（IID）的聚合物可以实现高电荷迁移率，但这些材料目前仅限于基于富勒烯的有机太阳能电池（OSC）。在这里，我们设计了一对替代的D-π-A型共聚物PE71和PE72，以扩展其在苯并[1,2- b：4,5- b' ]噻吩（BDT）的非富勒烯OSC中的应用。，噻吩并[3，2- b ]噻吩（TT）和IID单元分别用作D，A和π桥。优化TT桥上烷基链长度的目的是确保聚合物的溶解度，结晶度以及与受体分子的混溶性。我们发现PE71和PE72表现出相似的光学和电子特性，但是具有较短己基链的PE71倾向于聚集成纤维状结构。最后，由于合适的能级和互补的吸收光谱，选择Y 6作为电子受体。最后，PE71：Y6器件实现了12.03％的功率转换效率（PCE），明显高于PE72：Y6器件（9.74％）的转换效率，也是IID基光伏聚合物的最高值。系统地研究了电荷传输，分子聚集，薄膜形态和能量损失分析。PE71的改进的光伏性能：Y6主要源自更好的互穿网络结构，以促进激子分离和自由电荷载流子传输。我们的结果表明，基于IID的D-π-A聚合物也可用于非富勒烯OSC中，噻吩并[3,2 - b ]噻吩π桥上的烷基链对光伏性能具有至关重要的影响。