以薁为电子给体单元的新型近红外光伏材料的设计、合成及性能研究

The exploitation of novel near infrared (NIR) absorbing materials with high charge mobility is of great significance with regard to the enhancement of light-harvesting capability of photovoltaic devices in the NIR region of solar spectrum, and the key to this point lies in the development of novel electron donor (D) and electron acceptor (A) constructive units. Through careful structural analysis, we believe that azulene, the unique non-benzene aromatic unit with strong electron-donating capability and planar geometrical structure (which benefits to the intense intermolecular stacking), should be a quite promising D subunit in constructing small molecular NIR-absorbing photovoltaic materials with good carrier mobility. Hence in this project, we aim at the design and synthesis of novel NIR-absorbing materials bearing azulene D subunits but different A subunits, so that the role Azulene D subunits play in the construction of high-performance photovoltaic materials could be elucidated. Furthermore, the correlations between molecular structure and photophyiscal, electrochemical, molecular packing, charge-transporting properties as well as morphological properties of the photoactive blend films would also be investigated. The more potential materials would be selected as the electron-donating materials to fabricate integrated perovskite-heterojunction (BHJ) photovoltaic devices and multiple-donor BHJ photovoltaic devices, so that the relationship between molecular structure and photovoltaic properties could be studied. Through these research works, we could demonstrate whether azulene could act as a new promising structural unit in photovoltaic research field; and we could also develop some high-performance NIR-absorbing photovoltaic materials, which should be propitious to the enhancement of the power conversion efficiency of these low-cost solar cells.

开发具有高载流子迁移率的近红外吸收材料对改善光伏器件对近红外区太阳光谱的利用率具有重要意义，而其关键在于新型电子给体(D)/受体(A)结构单元的开发。薁，这一非苯芳香单元，不但具有极强的供电子能力，同时又有能促进分子间堆叠的大平板结构，极富潜力作为新型D单元以构建高性能近红外小分子光伏材料。本研究拟以薁及其衍生物作为D单元，将其与多种不同的A单元一起，构建出一类新型的近红外小分子吸收材料，深入研究薁单元独特的芳香性对材料的光物理、电化学、堆叠状态、迁移率及光活性层共混膜形貌的影响。筛选出性能优良的材料用于制作多主体单层本体异质结有机光伏（BHJ-OPV）器件及钙钛矿/BHJ-OPV集成器件，并探讨分子结构与光电性能的内在联系。通过本项目的完成，有望开发出薁这一全新的电子给体单元，并获得一系列新型高性能的近红外吸收材料，对提高低成本太阳电池的光电转化效率具有重要意义。

开发性能优异的近红外材料具有重要意义。本项目以薁片段为给电子单元，以方酸核、苯并噻二唑、吡咯并吡咯二酮、异靛蓝、噻吩并噻吩衍生物等为吸电子单元，设计、合成了一系列含薁光伏材料及其参比化合物，研究了薁单元对化合物的吸收、能级、堆叠、迁移率、光活性层共混膜形貌和光伏性能的影响。其中，含薁不对称方酸菁化合物仅靠简单结构就实现了低能隙、深HOMO能级和高迁移率的兼顾，获得了基于薁光伏材料的最高转换效率，和低能隙材料中的高开路电压。但研究中也发现，薁基光伏器件激子解离效率低且载流子复合高，是后续研究中需要特别注意的。本项目也通过高性能不对称方酸菁化合物的持续开发，不断推升方酸菁光伏材料的最高转换效率。更重要的是，在这些研究过程中，对方酸菁中心四元环的性质有了深入理解，为构建具有特异性的先进功能材料提供了一种新的思路和结构选择。