非富勒烯太阳能电池新型受体高分子材料的设计与合成

Non-fullerene solar cells have emerged as a hot research topic in the field of organic solar cells in recent years. The acceptor materials in such devices are not widely used fullerene derivatives but organic n-type small molecules or polymers. While the power conversion efficiency of non-fullerene solar cells based on small molecules has reached 12%, the one of polymer-based devices is around 8%. In order to improve the efficiency of latter, one can either modify the existing efficient acceptor polymers, for instance, naphthalene diimide (NDI)-based polymers, or develop a new class of n-type polymers. In this proposal, we will design and synthesize a new electron-withdrawing molecule, anthracene diimide (ADI), which can be used as the basic building unit to construct a series of polymers applied as the acceptor component to non-fullerene solar cells. The ADI molecule has an extended conjugation relative to NDI counterpart, resulting in a red-shifted absorption of ADI-based polymers compared to those containing NDI, which facilitates absorbing the near-infrared light of the solar spectrum for ADI polymers and thus improving the short-circuit current of devices. Moreover, ADI unit can be polymerized in two different ways producing two sorts of polymers with different backbone conformation, which will induce distinct polymer properties as well as their device performances. Therefore, ADI polymers are interesting models for studying the relationship between the molecular structure of acceptor polymers and their device behaviors, according to which the device performance could be adjusted by the molecular design. This work is supposed to provide a brand-new class of polymers that will be promising as acceptor materials for non-fullerene solar cells, and to enrich n-type material library for the research of organic electronics.

非富勒烯太阳能电池（nFSCs）是目前有机光伏领域的研究热点，其受体材料为n型有机小分子或高分子。基于小分子受体的器件效率已达12%，而高分子受体的器件效率在8%左右。为提高后者性能，可对现有高效受体如萘二酰亚胺（NDI）高分子进行优化，或者开发新的更高效的受体高分子。本项目旨在设计并合成一种新型拉电子单元，蒽二酰亚胺（ADI），构建基于此单元的受体高分子，并应用于nFSCs。ADI相对于NDI具有更大的π共轭体系，其高分子的吸收会比NDI高分子红移，有利于吸收近红外光以提高器件的短路电流。而且，ADI单元可在不同位置聚合得到两种不同主链构型的高分子，将带来材料诸多方面性质的差异，从而影响器件表现，所以ADI高分子将为研究受体高分子构效关系提供新的研究对象，并有利于通过分子结构调节器件性能。本项目将为nFSCs提供一类全新的、极具潜力的受体高分子材料，同时丰富有机电子学领域的n型材料体系。

本项目旨在设计并合成一种新型拉电子单元——蒽二酰亚胺，构建基于此单元的一系列n型高分子半导体材料，并应用于全高分子太阳能电池。项目执行期内，通过对合成路线的设计和优化，成功合成了两种基于蒽二酰亚胺单元不同对称位点双溴代的长烷基取代聚合单体，基于此进一步开发了多种新型蒽二酰亚胺类n型高分子半导体材料。研究了具有相同分子结构但主链连接方式不同的蒽二酰亚胺高分子构象异构体在光电性质、堆积行为、以及器件性能方面的差异；通过构建不同给受体组合并考察其共混薄膜形貌、结晶、和取向行为提出了给受体高分子的匹配原则；基于最优组合，对蒽二酰亚胺高分子受体材料的结构进行精细调控、选择合适的给体单元，最终取得了8.72%的全高分子太阳能电池光电转化效率。该项目的研究成果为有机太阳能电池的发展提供了新材料和新思路，同时丰富了有机电子学领域的n型材料体系，具有重要的科学意义。