高性能平面稠环电子受体光伏材料的设计与合成

In the field of organic solar cells (OSCs), the development of electron acceptor materials has lagged far behind that of donor materials. Fullerenes and their derivatives, particularly PC61BM and PC71BM, are the most widely used electron acceptors for solution processed OSCs. There remain incentives to develop non-fullerene acceptors that will not only retain the favorable properties of fullerenes, but also overcome their insufficiencies. However, high-performance non-fullerene acceptors remain rare, which is one of bottlenecks and challenging issues in this research field. In this project, we will design and synthesize high-performance planar fused-ring electron acceptor (FREA) materials with good solution processability, strong near infrared absorption, high electron mobility, suitable energy levels, and good miscibility with donors to form suitable phase separation. We will fabricate high-efficiency (13-18%), broad-photoresponse single-junction or tandem OSCs using narrow-bandgap FREAs and wide-bandgap polymer donors; or fabricate high-efficiency (>10%), high-transmittance (>40%) semitransparent OSCs using narrow-bandgap FREAs and narrow-bandgap polymer donors. We will explore fabrication of stable, high-efficiency, large-area, flexible non-fullerene OSCs. We will control aggregation and morphology by molecular engineering and processing engineering, and investigate effects of molecular packing, phase separation size and domain purity of the active layer on device performance. We propose to carry out device physics studies, particularly on photo-induced charge generation, charge transportation, charge recombination and energy loss mechanism, using ultrafast transient absorption and fluorescence spectra. We will also explore a fundamental understanding of molecular structure-morphology-device performance relationships of these FREA materials, which will in turn provide rational guide for design of new non-fullerene acceptors.

相对于电子给体，对电子受体的关注严重不足；相对于富勒烯受体，非富勒烯受体更被忽视。高性能非富勒烯受体的缺乏是制约有机太阳能电池发展的瓶颈之一。本项目针对非富勒烯受体的基本科学问题，设计创造有自主知识产权、综合性能优良的平面稠环电子受体新体系，特别是高迁移率、强近红外吸收的受体材料，打造国际同行认可的明星分子。与宽带隙的聚合物给体共混，构筑宽光谱响应、高效率（13-18%）的单结或叠层有机太阳能电池，或与窄带隙的聚合物给体共混，构筑高效率（> 10%）、高透光率(> 40%)的半透明太阳能电池，探索制备稳定、高效、大面积柔性器件。通过分子工程和器件加工工程来调控薄膜形貌和聚集态结构，研究活性层中分子堆积、相尺寸、相纯度对器件性能的影响。利用超快瞬态吸收和荧光光谱研究光生电荷产生、传输和复合以及能量损失的机制。理解分子结构、聚集态结构与光伏性能的关系，为高性能受体光伏材料的理性设计提供指导。

1995-2015年，富勒烯一直占据着电子受体这一关键有机光伏材料的统治地位。然而，富勒烯受体的诸多缺陷如吸光弱等导致其器件效率触碰天花板。另一方面，早期对替代富勒烯的新型电子受体的探索很少，其器件效率很低，且进展缓慢。因此，整个领域因为电子受体的制约遭遇发展瓶颈，发展高性能的新型受体材料是亟待解决的挑战性难题。本项目针对有机太阳能电池领域的挑战性科学问题，开展了创新性和系统性研究，取得如下重要结果：发展了若干分子设计策略，获得了具有不同结构特点的系列稠环电子受体材料和与之匹配的聚合物给体材料；构筑了效率高达18.7%的有机太阳能电池器件，制备的半透明太阳能电池器件当可见光区平均透过率为37.4%时效率为10.3%，柔性器件的效率达16.07%；建立了通过分子工程和器件工程调控分子聚集行为和活性层形貌的方法；研究了光生激子产生/解离、电荷生成/传输/复合以及能量损失的机理，发现稠环电子受体有别于富勒烯受体的新机制；揭示了稠环电子受体分子结构、聚集态结构与光伏性能的关系。. 项目执行期间，占肖卫或孙艳明以通讯作者在高水平期刊上发表105篇研究论文，包括Nat. Rev. Chem. 1篇、Nat. Rev. Mater. 1篇、Nat. Energy 1篇、Nat. Mater. 1篇、Nat. Photon. 1篇、Nat. Commun. 3篇、J. Am. Chem. Soc. 4篇、Angew. Chem. Int. Ed. 1篇、Acc. Chem. Res. 1篇、Adv. Mater. 14篇、Joule 1篇、Energy Environ. Sci. 4篇、Adv. Energy Mater. 8篇等。申请中国发明专利4项，获授权专利6项。科学出版社出版专著1部。培养博士毕业生10名，4名博士后出站。“稠环电子受体光伏材料”被提名高等学校科学研究优秀成果奖自然科学一等奖，通过会评，已公示无异议。. 我们创建了以明星分子ITIC为代表的稠环电子受体体系，我们的原创性工作引起了国内外同行的广泛关注和跟进，全球350多个研究组使用稠环电子受体制备高性能有机太阳能电池，效率远超富勒烯体系，现已超过20%，证明了稠环电子受体具有广泛的适用性。. 圆满完成了项目的研究计划，实现了项目的预期目标。