RIKEN Center for Emergent Matter Science (CEMS) , 2-1 Hirosawa , Wako, Saitama 351-0198 , Japan.
Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan.
ACS Appl Mater Interfaces. 2018 Mar 14;10(10):8901-8908. doi: 10.1021/acsami.7b19174. Epub 2018 Mar 1.
Surface-segregated monolayers (SSMs) based on two poly(3-alkylthiophene)s with semifluoroalkyl groups at either the side chains (P3DDFT) or one end of the main chain (P3BT-F) were used as self-organized buffer layers at the electrode interfaces in bulk heterojunction (BHJ) organic photovoltaic devices. Both of the SSMs greatly shifted the vacuum levels of the BHJ films at the surface due to the aligned permanent dipole moments of the semifluoroalkyl chains. Hole extraction in the BHJ of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C-butyric acid methyl ester (PCBM) became more efficient in the presence of the P3DDFT buffer layer, resulting in an improved power conversion efficiency. In contrast, the SSM of P3BT-F induced changes in the chain orientation of P3HT and the morphology of the BHJ films, resulting in decreased performance. These results indicate that the molecular design of polymer-based SSMs can affect not only the energy structure at the interface but also the morphology and the molecular orientations in the BHJs.
基于聚（3-烷基噻吩）的表面分离单层（SSM），其侧链（P3DDFT）或主链一端（P3BT-F）具有半氟烷基基团，被用作体异质结（BHJ）有机光伏器件中电极界面的自组织缓冲层。由于半氟烷基链的定向永久偶极矩，两种 SSM 都极大地改变了 BHJ 薄膜在表面的真空能级。在 P3HT：[6,6]-苯基 C-丁酸甲酯（PCBM）的 BHJ 中，存在 P3DDFT 缓冲层时空穴提取的效率更高，从而提高了功率转换效率。相比之下，P3BT-F 的 SSM 诱导了 P3HT 的链取向和 BHJ 薄膜形态的变化，导致性能下降。这些结果表明，基于聚合物的 SSM 的分子设计不仅可以影响界面的能量结构，还可以影响 BHJ 中的形态和分子取向。
