Tuning of polymer aggregation and optimization of the active layer morphology of all-polymer solar cells incorporating rylene-based acceptor polymers

本研究旨在通过优化电子接受相的电子输运特性来理解和提高聚合物基有机太阳能电池的光伏特性。本文将合成以萘二酰亚胺为基料的新型“低带隙”电子接受共聚物，提高其电子迁移率。这些共聚物的HOMO和LUMO能级是为与公认的供电子聚合物如聚（3-己基噻吩）（P3HT）结合而设计的。将研究纯聚合物和共混聚合物中的电子输运及其与光伏器件性能的关系。为了优化这些块状异质结器件的光学和电子传输性能，将研究由供电子聚合物、接受电子聚合物和众所周知的可溶富勒烯PCBM组成的三元共混物的形貌、电荷传输和太阳能电池性能。因此，通过化学设计来调整受体聚合物相对于PCBM能量结构的LUMO水平将是本项目的重要任务之一。通过使用具有低带隙的受体聚合物，设想了宽光谱覆盖。最后，将研究嵌段共聚物或低分子量软化剂（和表面活性剂）等添加剂对聚合物-聚合物共混物形貌的影响，目的是开发具有高载流子解离和萃取效率的聚合物共混物的新方法。

The proposed work aims at the understanding and the advancement of the photovoltaic properties of polymer-based organic solar cells by optimizing the electron-transport properties of the electron-accepting phase. Novel “low bandgap” electron-accepting copolymers based on naphthalenebisimide with improved electron mobility will be synthesized. The HOMO and LUMO energy levels of these copolymers are designed for a combination with well-established electron-donating polymers such as poly(3-hexylthiophene) (P3HT). Electron-transport in the pure polymer and in the blend will be studied and related to the photovoltaic device performance. In order to optimize the optical and electron-transporting properties of these bulk-heterojunction devices, ternary blends comprising an electron-donating polymer, an electron accepting polymer and the well-known soluble fullerene PCBM will be investigated with respect to morphology, charge transport and solar cell properties. Hereby, the adjustment of the LUMO level of the acceptor-polymer with respect to the energetical structure of PCBM by chemical design will be one important task of this project. By using acceptor polymers with low bandgap, wide spectral coverage is envisaged. Finally, the influence of additives as block copolymers or low molecular weight softeners (and surfactants) on the morphology of polymer-polymer blends will be investigated, with the goal to develop novel approaches towards polymer blends with high charge carrier dissociation and extraction efficiencies.