Herein, three benzodithiophene (BDT)-based conjugated polymers, PBDTT-FBT, P3TBDT-FBT, and PTBOT-FBT, with gradually increased biaxially-extended side-chain conjugation are synthesized. The increase in the side-chain conjugated plane is revealed to enhance the π-π* transition and intramolecular charge transfer (ICT) of the polymer to result in improved absorption at near-ultraviolet region. Besides, the electron-withdrawing ability of the large side-chain conjugation effectively downshifts the energy levels of the derived polymer. Through providing complementary absorption spectra and suitable cascade energy levels, PTBOT-FBT with the largest side-chain conjugation is demonstrated as an effective third photoactive component for both fullerene and non-fullerene-acceptor (NFA) binary bulk-heterojunction (BHJ) systems, which enables a respective improvement of 2.5% and 11.8% in PCE of the studied fullerene- and NFA-based ternary solar cell devices. Moreover, it is found that the ternary NFA-based BHJ film exhibits a more favorable morphology after adding PTBOT-FBT as compared to the fullerene-based film, suggesting the higher tolerance of the polymers with bulky sidechains in the NFA system.

在此，合成了三种苯并二噻吩（BDT）基共轭聚合物PBDTT-FBT，P3TBDT-FBT和PTBOT-FBT，它们的双轴延伸侧链共轭逐渐增加。揭示了侧链共轭平面的增加可增强聚合物的π-π*跃迁和分子内电荷转移（ICT），从而改善近紫外区域的吸收。此外，大侧链共轭的吸电子能力有效地降低了衍生聚合物的能级。通过提供互补的吸收光谱和合适的级联能级，PTBOT-FBT具有最大侧链共轭的化合物被证明是富勒烯和非富勒烯受体（NFA）二元本体-异质结（BHJ）系统的有效第三种光敏组分，可使PCE的PCE分别提高2.5％和11.8％。研究了基于富勒烯和NFA的三元太阳能电池器件。此外，发现与基于富勒烯的膜相比，基于PTAOT-FBT的三元基于NFA的BHJ膜表现出更有利的形态，表明在NFA体系中具有大侧链的聚合物具有更高的耐受性。