基于偶极矩调控和侧链修饰的新型聚合物材料的设计、制备与光电性能研究

Polymer solar cells have showed a broad application prospect because of their advantages such as low cost, light weight, flexibility and ease of large-area processing. However, the relatively low dielectric constant and high exciton binding energy (0.3-0.5 eV) in conjugated polymers primarily limit the effective charge separation and lead to charge recombination, which hence can reduce the efficiency of polymer solar cell. In this project, we present a new polymer molecule design by combining the manipulation of dipole moment and side chain modification together. First, a side-chain donor-acceptor conjugated polymer structure is employed with the main chain constructed by donor moieties and the acceptor units conjugatedly pended onto the donor unit in the side chain. On the basis of density functional theory calculation, the dipole moment of polymer is optimized by tuning the side chain structure of polymer to promote the electron to be concentrated in the side chain and hence facilitate charge separation as well as reduce charge recombination. In addition, naphthalene group is introduced to the side chain to improve the miscibility with fullerene derivatives and induce the aggregation of fullerene derivatives in the side chain units, which will provide the fast charge transfer and formation of nanoscale bicontinuous pathway for better charge transport. A series of novel side-chain donor-acceptor polymers will be prepared to systematically investigate the influence of dipole moment and naphthalene group modification on the film morphology and photovoltaic properties. Furthermore, the mechanism of charge separation, charge transport, charge recombination induced by dipole moment manipulation will be explored.

聚合物太阳能电池因具有工艺简单、成本低、重量轻、可制成柔性器件等突出优点，具有显著的应用前景。 然而由于聚合物低的介电常数和高的激子束缚能，电荷分离困难，复合现象严重，限制了光电性能的提高。本项目通过将分子偶极矩调控和侧链修饰协同起来，对聚合物分子结构进行设计优化。采用主链给体-侧链受体的共轭聚合物结构，结合理论模拟计算，一方面对其分子偶极矩进行调控，并利用给受体的推拉电子体系,以减少电子和空穴之间的束缚力，使得光激发后电子在侧链聚集，促进电荷的分离，减少电荷复合；另一方面开创性的在侧链接枝萘基团，以改进与富勒烯衍生物的相容性，诱导富勒烯衍生物在侧链处的聚集，促使侧链处富集的电子得以迅速转移和混合膜中互穿网络结构的形成。制备一系列新型聚合物材料，系统的研究分子结构改变对电荷分离、电荷传输、电荷复合、本体异质结混合膜形貌、光电性能等的影响，并探索其内在机制和影响规律。

有机光电聚合物具有制备简单、成本低廉、重量轻及可制成柔性器件等突出优点, 近年来成为国内外研究的前沿和热点。作为聚合物太阳能电池的重要功能层材料，共轭聚合物的性能优化是提高器件效率的重要途径。目前对聚合物材料主链结构的优化研究较多, 基于侧链调控的报道则相对较少. 以往侧链引入的目的主要是改善材料的溶解性能, 然而, 侧链基团的影响远非如此.研究发现, 侧链修饰后聚合物材料的吸收光谱、能级分布、载流子迁移率、器件共混膜形貌以及界面形态等光电性能方面可发生不同程度的变化.本课题对聚合物侧链进行创新性的分子结构设计,系统的研究侧链修饰对聚合物性能的影响。.首先，通过对聚合物给体材料分子侧链结构进行修饰改性，实现了混合膜形貌的自组装优化。活性层膜形貌的改变主要是由于侧链修饰后聚合物分子链的聚集性质、材料表面能、界面偶极矩及与受体材料的相容性发生了不同程度的变化。可有助于缩短光电池的制作工艺，降低生产成本。.其次，对侧链末端稠环基团修饰，一方面可诱导聚合物链形成短程有序聚集体，有利于电荷的传输。另一方面避免了结晶度的提高，有利于在柔性器件领域的应用。.此外，研究发现聚合物材料侧链可有效影响聚合物链的排列形态，导致二面角发生变化，进而影响分子平面性、主链有效共轭程度及聚合物链间π-π相互作用, 故而会对聚合物吸收光谱、能级分布、载流子迁移率、界面偶极矩和偶极子、共混膜形貌及界面形态等方面会产生不同程度的影响。.本课题发表与项目相关SCI论17篇,申请专利2项。