梯形窄带隙稠环共轭分子的设计、合成、性质及其光伏性能研究

The design and synthesis of low bandgap pi-conjugated functional molecules is the key to realize high-performance organic photovoltaics and thus of great scientific importance. High carrier mobility, broad absorption, suitable electronic energy level and good stability/processibility are the primary requirements of organic photovoltaic materials for highly efficient photon-electron conversion. Here we designed polycyclic conjugated systems featured by ladder-type molecular structure. In contrast to 6-6-fused ring system of the classical acenes, the HOMO/LUMO energy levels of the ladder-type molecules can be effectively lowered by the aromatic tendency of unsaturated five-membered ring, which results in narrow bandgap and enhanced ambient,thermal-,photo-,electrochemical and even device stability. The project on the one hand will develop new and efficient synthetic methods for the construction of polycyclic structures that are of great synthetic challenges. The "cascade" strategy will be utilized for the multiple carbon-carbon formations.The selective functionalization of the ladder-type molecules will be realized to give a molecular library for property study and device applications. On the other hand, the relationships among molecular structures, the aggregation style, the related physical properties and photovoltaic performance will be studied in detail.The stability condundrum that limits the practical application of acenes will be finally solved without the sacrifice of carrier mobility. Furthermore, several conjugated functional units will be developed owing novel and efficient singlet-fission property, which provides the possiblity of breaking Shockley-Queisser limit. The project will significantly promote the development of organic photovoltaic materials for high-performance small-molecule organic solar cells.

窄带隙共轭分子的设计与合成是实现高性能有机太阳能电池的基本要素，有着十分重要的科学意义。本项目针对高效光电转换对有机光伏材料高迁移率、宽吸收光谱、电子能级匹配性和稳定性等基本要求，设计了具有梯形结构的窄带隙稠环共轭分子，从中筛选若干具有高效单线态裂变特性的共轭功能单元，为太阳能电池突破Shockley-Queisser理论效率极限提供可能。与经典的稠环芳烃-并苯的6-6并环结构不同，借助于不饱和五元碳环的芳香化特征，有效降低梯形共轭分子的HOMO/LUMO能级水平并提高其空气、热、光、电化学乃至器件稳定性。本项目一方面开发（杂）多环结构的高效构筑方法，实现梯形分子的选择性官能化，获得可供性质/光伏器件研究的梯形分子材料库；另一方面研究梯形分子结构等对固态堆积方式、光电物理性质和光伏器件性能的影响规律。该项目将为推动高性能小分子太阳能电池的开发发挥重要作用。

窄带隙共轭分子的设计与合成是实现高性能有机太阳能电池的基本要素，有着十分重要的科学意义。本项目针对高效光电转换对有机光伏材料高迁移率、宽吸收光谱、电子能级匹配性和稳定性等基本要求，设计了具有梯形结构的窄带隙稠环共轭分子。与经典的稠环芳烃-并苯的6-6并环结构不同，借助于不饱和五元碳环的芳香化特征，有效降低梯形共轭分子的HOMO/LUMO能级水平并提高其空气、热、光、电化学乃至器件稳定性。就二并苯并[a,e]戊搭烯衍生物开发出一种高效的氧化还原中性异相催化系统，Pd(OAc)2/n-Bu4NOAc，其具有良好的底物适应性；我们合成了系列二苯并戊搭烯、二萘并戊搭烯和二蒽并戊搭烯化合物，对其光电性质研究发现二蒽并戊搭烯表现出强烈的黄色荧光特性，理论研究表明与二苯并及二萘并戊搭烯相比，只有二蒽并戊搭烯的S1态跃迁通道是打开的。设计合成了三种具有大立体位阻二叔丁基苯基取代的二并苯并[a,e]戊搭烯衍生物，随着分子共轭骨架的延长；分子堆积可以通过pi-表面和烷基或芳基取代基之间的平衡予以调节，形貌的理论计算与实验结果取得了很好的抑制。制备了基于二蒽并[a,e]戊搭烯空气稳定的场效应晶体管，其表现出优异的空穴迁移率，达到6.55 cm2 V-1 s-1；本研究表明二蒽并[a,e]戊搭烯尽管具有超大的pi拓展共轭表面依然具有很好的稳定性，为探索高性能半导体材料研究提供了优秀的分子平台。本项目一方面开发（杂）多环结构的高效构筑方法，实现梯形分子的选择性官能化，获得可供性质/光伏器件研究的梯形分子材料库；另一方面研究梯形分子结构等对固态堆积方式、光电物理性质和光伏器件性能的影响规律。