A series of new donor–acceptor π-conjugated copolymers incorporating 5,10-dihydroindolo[3,2-b]indole (DINI) as an electron donating unit have been designed, synthesized, and explored in bulk heterojunction solar cells with diketopyrrolopyrrole and thienopyrroledione as the electron accepting units. A significant effect of the size and shape of the pendant alkyl substituents attached to the DINI unit on the optical and electronic properties of the copolymers is described. Our study reveals a good correlation between the theoretical calculations performed on the selected materials and the experimental HOMO, LUMO, absorption spectra, and band gap energies of the corresponding copolymers. The band gaps of the conjugated copolymers can be tailored over 0.4 eV by the electron-withdrawing nature of the different acceptor units to provide better overlap with the solar spectrum, and the energy levels can be tuned ∼0.2 eV depending on the alkyl substituents employed. For the polymers in this study, a nonoptimized power conversion efficiency as high as 3% was observed.

中文翻译：

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5,10-二氢吲哚[3,2- b ]吲哚基共聚物，具有交替的供体和受体结构，适用于有机光伏

一系列含有5,10-二氢吲哚[3,2- b]的新的供体-受体π共轭共聚物在以二酮吡咯并吡咯和噻吩并吡咯二酮为电子接受单元的体异质结太阳能电池中，设计，合成和研究了作为电子给体的吲哚（DINI）。描述了连接至DINI单元的烷基侧基取代基的大小和形状对共聚物的光学和电子性能的显着影响。我们的研究揭示了在所选材料上进行的理论计算与相应共聚物的实验HOMO，LUMO，吸收光谱和带隙能之间的良好相关性。共轭共聚物的带隙可以通过不同受体单元的吸电子特性调整到0.4 eV以上，以更好地与太阳光谱重叠，并且能级可以调整为〜0。2 eV，取决于所用的烷基取代基。对于本研究中的聚合物，观察到高达3％的非优化功率转换效率。