基于四嗪为受体单元共轭聚合物的设计、合成及光伏性能研究

Polymer solar cell (PSCs) related study has become one of the hottest research areas due to its advantages over conventional counterparts: low cost, easy processing, flexibility and larger area. The development of efficient polymer donor materials is considered to be the key point for the improvement of power conversion efficiency. And this is the goal of our project. Based on our previous research results, we propose a method for the synthesis of Donor-Acceptor (D-A) copolymer composed of BDT as electron-donating unit and Tetrazine as electron-accepting unit. With increasing number of acromatic rings in both sides, electron-donating ability is enhanced; being copolymerized with Tetrazine electron-accepting unit, intra-molecular charge transfer state (ICTs) will be impoved; all these adjustments guarantee a lower band gap, and thus a broader absorption band. At the meantime, BDT unit has a large and rigid planar structure, which favors the π-π stacking in solid state, thus favors the charge carrier transportation. All of these quantities together make the Tetrazine-based polymers attractive. Active layers, including polymer and PCBM, can be used for further investigation of how molecular structure would affect blend aggregation, to reveal the relationship between molecular structure and photovoltaic properties, and to provide experimental basis for molecular design of PSC materials.

聚合物太阳能电池以其成本低、制作工艺简单、可制成柔性大面积器件等突出优点，成为当前的热点研究领域之一。开发性能优异的给受体型聚合物材料是提高太阳能电池光电转换效率的关键。本项目拟在我们前期工作基础之上，通过在苯并二噻吩（BDT）单元两侧增加芳香环数目，来增加给体单元的给电子能力，与吸电子的四嗪单元共聚，构筑新型给受体型（D-A）共轭聚合物，通过增强分子内电荷转移（ICT）强度，进一步增大聚合物分子的吸收范围，降低带隙；同时，苯并二噻吩（BDT）衍生物大的刚性共平面结构，有利于固态结构中分子间的π-π堆积，从而提高了聚合物载流子的传输，进而获得一系列基于四嗪为受体单元的窄带隙、宽吸收、高载流子迁移率的共轭聚合物材料。以合成的聚合物为给体，PCBM为受体制备活性层，研究聚合物的分子结构与薄膜聚集态的关系，揭示聚合物分子结构与光电转换效率之间的关系，为聚合物太阳能电池材料的分子设计提供实验依据。

有机太阳能电池以其成本低、制作工艺简单、可制成柔性大面积器件等突出优点，成为当前的热点研究领域之一。开发性能优异的给受体型有机共轭分子是提高有机太阳能电池能量转换效率的关键。本项目以苯并二噻吩（BDT）、二噻吩并环戊二烯类（DTS）作为给电子单元，以1，2, 4, 5-四嗪、苯并噻二唑为受电子单元设计合成了一系列新型的给受体型有机共轭太阳能电池材料。在项目中，我们以合成的有机共轭分子作为给体材料，以PCBM（PC71BM，PC61BM）作为受体材料，制备了体异质结型有机太阳能电池器件。在实验中，我们通过改变给体材料和受体材料的组分比、溶剂、以及加入添加剂（DIO）的比例等，来调控有机活性层的聚集态微观结构，研究有机给体材料的分子结构与活性层光敏薄膜的聚集态的关系，进而揭示有机共轭分子结构与器件的能量转换之间的关系。本项目中设计合成的聚合物PBDT-DTffBT，展现了与PCBM合适的能级结构，有机太阳能电池器件结果：短路电流为15.2 mA/cm2，开路电压为 0.86 V，填充因子为0.69，能量转换效率达到9.01%。