弱键力和液晶驱动给受体协同自组装调控聚合物/富勒烯体相异质结活性层形貌及光伏性能

The ability to control the morphology of liquid crystals and intermolecular weak bond force provides opportunities to fine-tune Bulk Heterojunction (BHJ) active layer nanostructures in polymer/fullerene solar cells. An easy-to-process and feasible strategy to achieve highly ordered BHJ morphology with bi-continuous nanoscale interpenetrating network is developed by rationally designing liquid crystalline polymer donors (D)and mesogen-modified fullerene acceptors (A)to create liquid crystalline donor-acceptor nanocomposites containing the intermolecular weak bond interaction (electrostatic force and hydrogen bond), which can control the complexes stacking induced by cooperative assembly between donor and acceptor. In such supramolecular systems, both mesogen and intermolecular interaction would drive cooperative assembly between donors and acceptors to construct heterojunction at molecular levels. More importantly, cooperative assembly would likely lead to bi-continuous nanoscale morphology to facilitate charge mobility and this obtained self-assembly nanostructures also can be further stabled by intermolecular weak bond interaction. The effect of the cooperative assembly between donors and acceptors on the active morphology and photovoltaic performance will be studied, and the relationship of the structure, morphology and device performance will be also established. Finally, high performance photovoltaic devices based on this highly ordered donor-acceptor nanocomposites as active layer will be fabricated and optimized.

本项目利用分子间弱键作用和液晶强大的形貌控制能力来调控聚合物/富勒烯太阳能电池的体相异质结活性层形貌，提出一种简易而有效的、构筑纳米尺度上的双连续有序体相异质结结构的新方法，即将光伏性能优异的聚合物给体（D）材料和富勒烯受体（A）材料同时设计成具有液晶特性的、可形成分子间弱键（如氢键、静电力等）的分子。利用分子间弱键作用和液晶超强自组装特性来诱导和驱动D材料与A材料的协同组装，从而构建分子水平上均一异质结，获得有利于载流子高效传输的、纳米尺度微相分离的、D/A双连续体相异质结结构，而且这种有序超分子结构还可以在分子间弱键力的作用下进一步得到稳定。深入研究给、受体协同组装对体相异质结活性层微观形貌和光伏性能的调控机制，建立分子结构、微观形貌和器件性能三者之间的关系。最后，在此基础上，以此微观结构有序的D/A纳米复合体系为活性层，制备高性能聚合物/富勒烯太阳能电池，并进行器件优化。

有机太阳能电池给体和受体形成的体相异质结界面形貌严重影响了电荷的分离和传输，从而影响器件的性能。本项目将各类液晶基元（棒状、盘状）和可形成分子弱键的结构引入到给体材料和受体材料中，研究发现，液晶的自组装和分子间弱键作用可以有效驱动给体材料和受体材料的协同组装，实现了分子水平上的异质结有序界面的构建，电荷的分离和传输效率以及最终的器件效率得到明显的提高。同时，协同组装体系可以很好地稳定异质结有序界面形貌，有效的提高了器件的稳定性。深入研究了液晶和弱健力驱动下给体和受体材料之间的协同组装机制，对给受体纳米复合体系组装形貌和器件性能的调控作用。另外，将液晶静电组装等方法进一步引入到界面层中调控界面偶极取向，降低界面势垒，提高了界面电荷提取和收集效率。并在此基础之上，探索了全溶液加工方法制备高效有机太阳能电池，为未来大面积制备有机太阳能电池提供理论和实验指导。