State Key Laboratory of Polymer Physics and Chemistry, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, P. R. China.
Acc Chem Res. 2014 May 20;47(5):1595-603. doi: 10.1021/ar5000743. Epub 2014 Apr 29.
As researchers continue to develop new organic materials for solar cells, benzo[1,2-b:4,5-b']dithiophene (BDT)-based polymers have come to the fore. To improve the photovoltaic properties of BDT-based polymers, researchers have developed and applied various strategies leading to the successful molecular design of highly efficient photovoltaic polymers. Novel polymer materials composed of two-dimensional conjugated BDT (2D-conjugated BDT) have boosted the power conversion efficiency of polymer solar cells (PSCs) to levels that exceed 9%. In this Account, we summarize recent progress related to the design and synthesis of 2D-conjugated BDT-based polymers and discuss their applications in highly efficient photovoltaic devices. We introduce the basic considerations for the construction of 2D-conjugated BDT-based polymers and systematic molecular design guidelines. For example, simply modifying an alkoxyl-substituted BDT to form an alkylthienyl-substituted BDT can improve the polymer hole mobilities substantially with little effect on their molecular energy level. Secondly, the addition of a variety of chemical moieties to the polymer can produce a 2D-conjugated BDT unit with more functions. For example, the introduction of a conjugated side chain with electron deficient groups (such as para-alkyl-phenyl, meta-alkoxyl-phenyl, and 2-alkyl-3-fluoro-thienyl) allowed us to modulate the molecular energy levels of 2D-conjugated BDT-based polymers. Through the rational design of BDT analogues such as dithienobenzodithiophene (DTBDT) or the insertion of larger π bridges, we can tune the backbone conformations of these polymers and modulate their photovoltaic properties. We also discuss the influence of 2D-conjugated BDT on polymer morphology and the blends of these polymers with phenyl-C61 (or C71)-butyric acid methyl ester (PCBM). Finally, we summarize the various applications of the 2D-conjugated BDT-based polymers in highly efficient PSC devices. Overall, this Account correlates the molecular structures of the 2D-conjugated BDT-based polymers with their photovoltaic properties. As a result, this Account can guide the molecular design of organic photovoltaic materials and the development of organic materials for other types of optoelectronic devices.
作为研究人员继续开发用于太阳能电池的新型有机材料，苯并[1,2-b:4,5-b']二噻吩（BDT）基聚合物已经成为研究热点。为了提高 BDT 基聚合物的光伏性能，研究人员已经开发并应用了各种策略，从而成功地对高效光伏聚合物进行了分子设计。由二维共轭 BDT（2D-conjugated BDT）组成的新型聚合物材料将聚合物太阳能电池（PSC）的功率转换效率提高到了超过 9%的水平。在本综述中，我们总结了最近在设计和合成 2D-共轭 BDT 基聚合物方面的进展，并讨论了它们在高效光伏器件中的应用。我们介绍了构建 2D-共轭 BDT 基聚合物的基本考虑因素和系统的分子设计准则。例如，只需将烷氧基取代的 BDT 修饰为烷基噻吩基取代的 BDT，就可以大大提高聚合物的空穴迁移率，而对其分子能级几乎没有影响。其次，向聚合物中添加各种化学基团可以使 2D-共轭 BDT 单元具有更多的功能。例如，引入具有缺电子基团（如对烷基苯基、间烷氧基苯基和 2-烷基-3-氟噻吩基）的共轭侧链，使我们能够调节 2D-共轭 BDT 基聚合物的分子能级。通过对 BDT 类似物（如二噻吩并苯并二噻吩（DTBDT）或更大的π桥的插入进行合理设计，我们可以调节这些聚合物的主链构象并调节它们的光伏性能。我们还讨论了 2D-共轭 BDT 对聚合物形态的影响以及这些聚合物与苯基-C61（或 C71）-丁酸甲酯（PCBM）的共混。最后，我们总结了 2D-共轭 BDT 基聚合物在高效 PSC 器件中的各种应用。总体而言，本综述将 2D-共轭 BDT 基聚合物的分子结构与其光伏性能相关联。因此，本综述可以指导有机光伏材料的分子设计和其他类型光电设备用有机材料的开发。
