用于聚合物太阳电池给体材料的新型嵌段共轭聚合物

Recently, much attention has been focused on high performance polymer solar cells (PSCs), however, conjugated polymers that were employed as electron-donors typically exhibited unmatched absorption spectra with solar spectrum, which has become one of the greatest challenges for further improvement of power conversion efficiency of PSCs. In order to develop conjugated polymers with appropriate absorption profile that can harvest solar energy more efficiently, we proposed a set of novel conjugated block copolymers with broad complementary absorption that can be synthesized by covalently connecting poly(3-alkylthiophene)s (P3AT) and "donor-acceptor" (DA) type of narrow band-gap conjugated copolymer, poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-(5-fluoro-(4,7-(2,1,3-benzothiadiazole))] (PCPDFBT) via "click" reaction. The proposed conjugated block copolymers were supposed to exhibit absorption profiles of both P3AT that ranged ca. 400-650 nm and DA-type of copolymers that ranged ca. 550-900 nm, leading to comparatively broad absorption band that can cover the range of 400-900 nm, which would dramatically improve the harvest of solar energy and may thereby result in improved short circuit current and power conversion efficiency. Additional efforts focused on more rational molecular design along with the fine control of block lengths may allow for the optimization of bulk-heterojunction films processing in terms of microscale phase separation, film morphology as well as charge carrier mobilities, and may finally provide a new strategy for the molecualr design of high performance donor polymers for PSCs.

目前困扰聚合物太阳电池能量转换效率提高的最大挑战之一是用作电子给体的共轭聚合物的吸收光谱与太阳光谱不匹配，太阳光利用效率低。发展宽吸收的共轭聚合物用于有机薄膜太阳电池给体，有望显著提高太阳光利用效率。本申请拟通过"点击"化学反应将不同分子量的聚烷基噻吩衍生物以及"给体-受体"结构的窄带隙共轭聚合物聚（(二噻吩并环戊二烯)-alt-(5-氟苯并噻二唑)，PCDTFBT）通过共价键方式连接，制备一系列新型嵌段共轭聚合物。拟制备的嵌段共轭聚合物将同时具有P3HT在400-650 nm以及PCDTFBT在550-900 nm的吸收特性，其吸收光谱可覆盖400-900 nm的范围，可大大提高对太阳光的吸收，有望显著提高太阳光利用以提高太阳电池器件的光电转换效率。此外，通过对单个嵌段的分子结构进行化学改性及控制两个嵌段的比例，可有效调控嵌段共轭聚合物的微相分离，有望得到高性能的聚合物太阳电池。

作为清洁可再生能源，太阳能具有取之不尽、不受地域限制等独特优势。利用太阳能的有机/聚合物太阳电池由于其具有制作成本低、可采用“辊对辊”工艺制备柔性器件等独特优势，近年来引起了产业界和学术界的极大关注。.发展聚合物太阳电池的关键是如何有效的吸收太阳光的能量，以及如何将吸收的能量转换为光电流，保证载流子传输到电极，并实现有效的收集。本项目首先通过合理的分子设计，获得高光电转换效率的聚合物太阳电池材料体系，进一步在材料的基础上制作电池器件，并对薄膜的形貌、器件结构等进行优化，获得高光电转换效率的聚合物太阳电池器件。. 本项目取得的重要进展包括：. 1）本项目将吸收互补的宽带隙聚合物给体材料与富勒烯受体材料、非富勒烯受体材料结合，发展了“三元体系聚合物太阳电池”，不仅有效拓宽吸收光谱的范围，使器件的光电转换效率从6%提高到8%以上，同时大大简化了光活性层的制作工艺。. 2）通过将极性单元引入到共轭聚合物的侧链，首次成功发展了一种给受体型聚合物添加剂。引入这种添加剂可以有效改善体异质结活性层的形貌，将聚合物太阳电池光电转换效率从6%左右提高到7.9%，具有非常广阔的应用前景。. 3）本项目成功发展了一系列高性能的聚合物太阳电池材料。其中发展的基于萘并噻二唑结构的共轭聚合物材料光电转换效率超过10%。这类材料可以在厚度1微米的薄膜，实现光电转换效率超过8%，这是目前公开报道的厚膜器件的最高效率。. 4）发展了一系列新型的宽带隙共轭聚合物太阳电池材料，代表性的聚合物为基于酰亚胺并苯并三唑单元的共轭聚合物材料，光学带隙达到约1.8 eV。通过系统的器件优化，获得的光电转换效率达到8.63%，这是目前报道的效率的最高的宽带隙材料之一。