基于酰亚胺取代苯并二噻吩衍生物的聚合物受体光伏材料的合成与性能研究

Polymer solar cells (PSCs) have advantages of easy adjustment of properties, excellent mechanical properties, liable to form interpenetrating network structure with stable microphase separation, and consequently are appropriate to fabricate large area, flexible photovoltaic devices through low-cost solution-processable techniques. Therefore, all-polymer solar cells based on polymer donor/polymer acceptor is the trend in organic photovoltaic and solar cells industry development. Up to now, the power conversion efficiency (PCE) of the all-polymer solar cells has been beyond 8%. However, the development of polymer acceptor still lags far behind that of PCBM and small molecular acceptor materials, which is the main constraint on development of all-polymer solar cells. Thus, it is of prime importance to design and synthesize novel building blocks for polymer acceptor materials.. In this research, we design and synthesize BDI derivatives, which combining the star building block of benzo[1,2-b:4,5-b′]dithiophene (BDT) with strong electron-withdrawing imide substitution. The electron-defect BDI derivatives will be copolymerized with a series common used aromatic rings such as thiophene, dithiophene, fluorene, carbazole, benzoditiophene, benzodifuran, thienothiophene, and so on, to form a series of novel conjugated polymers used in solar cells. By this means, the polymers will possess enhancement charge carrier mobility as well as low band gaps and broad absoption. The target of this project will focus on developing new electron-defect building blocks and corresponding acceptor polymers and get insights into the relationship of the structures, properties, and photovoltaic performance of the BDI-based polymer acceptor materials. Fine tuning on the molecular levels and absorption spectra of these polymers will be accomplished through systemic molecular modifications. That means the new molecular design strategy will accelerate the development of conjugated polymer photovoltaic materials in theory and reality.

聚合物光伏材料具有各项性能易调控、机械性能优异、易于形成互穿网络结构、相结构稳定性好等优点，利于制备大面积柔性器件，并保证器件的长期稳定性。因而，基于聚合物给体/聚合物受体的全聚合物太阳能电池，是聚合物太阳能电池发展的方向，也是大规模产业化生产应用的首选。迄今为止，全聚合物太阳能电池光电转换效率已经达到8%。然而，相对于PCBM和小分子受体材料，聚合物受体材料的光伏性能仍较低，是制约全聚合物太阳能电池发展的瓶颈。本研究工作提出了将光电性能优异的苯并二噻吩单元(BDT)，与具有强吸电子作用的酰亚胺取代基相结合，设计出苯并二噻吩四甲酰二亚胺(BDI)构筑单元，并设计合成一系列基于该类新型共轭单元的聚合物受体光伏材料。在发挥苯并二噻吩单元优异的光电性能的基础上，填补了苯并二噻吩缺电子衍生物及相关聚合物材料的空白，期望获得一类新型高性能聚合物受体材料，对聚合物光伏材料的发展做出一定的贡献。

聚合物光伏材料具有各项性能易调控、成膜加工性能好、机械性能优异、易于形成连续互穿网络结构、相结构稳定性好等优点，适合制备大面积柔性太阳能电池，并保证器件性能的长期稳定。因而，基于聚合物给体/聚合物受体的全聚合物太阳能电池，是聚合物太阳能电池发展的重要方向，具有大规模产业化生产应用的潜力。酰亚胺类共轭聚合物材料是最重要的聚合物受体光伏材料之一，其中，基于萘酰亚胺单元的共轭聚合物N2200是最具代表性的聚合物受体(n型共轭聚合物)材料之一。然而，传统的酰亚胺类聚合物(主要是萘酰亚胺和苝酰亚胺)，由于萘酰亚胺和苝酰亚胺单元的电子局域性强，聚合物中分子内电荷转移很不充分，导致酰亚胺类聚合物材料吸收性能较差，制约了该类材料的光伏性能。本研究工作将共轭性能适中的苯并二噻吩单元(BDT)，与强吸电子作用的酰亚胺取代基相结合，合成出苯并二噻吩四甲酰二亚胺(BDI)构筑单元，并制备了一系列基于该类新型共轭单元的聚合物受体光伏材料。由于共轭性的增强，电子离域性的提高，BDI类共轭聚合物实现了较充分的分子内电荷转移，相应地，该类聚合物表现出强可见光-近红外吸收。以PBDB-T为给体材料、BDI类聚合物PB2T1为受体材料的全聚合物太阳能电池实现了接近8%的光电转换效率，添加PC71BM为第三组分的太阳能电池光电转换效率达到10%，基本实现了本研究工作的预期目标，体现出了BDI单元在聚合物受体光伏材料中的应用潜力，为聚合物受体光伏材料以及全聚合物太阳能电池的研究提供了新的思路。