Near IR sensitization of polymer/fullerene solar cells: controlling the morphology and transport in ternary blends

设计和开发三元体异质结（BHJ）复合材料需要研究有机半导体和光伏的三个独立方面和基本主题。合成：该项目将从用于传输矩阵和敏化剂的现有聚合物开始，然后迅速转向为近红外敏化而定制的新型聚合物，即具有各种带隙和较小的HOMO位置变化。形貌：三元BHJ复合材料的形貌评估和形貌控制将是本项目的另一个挑战。相互之间不能完全混溶的聚合物（这是常见的情况）在溶液中和在固态中都会出现脱混现象。根据希尔德布兰特的理论，如果聚合物具有相当的分子间粘附力，那么它们就可以相互混溶。我们对三元体系中相分离机制的理解和研究将基于类似汉森理论的方法。通过评估单个组分的溶解度参数，我们研究了三元复合材料的汉森球。输运和电荷转移：二元BHJ复合材料中的输运已经是一个复杂的过程。在这个项目中，我们将研究三元复合材料的输运机制。具体来说，我们将探索合适的实验方法，以区分两种聚合物的作用及其对空穴输运的各自贡献。与输运同样重要的是三元共混体系中的电荷产生过程。时间分辨泵浦探测光谱在ns体制将被用来了解如何两种聚合物相互作用。最重要的是，我们想弄清楚这两种聚合物是否会表现出直接的电荷转移、能量转移，甚至没有电子相互作用。

The design and development of ternary bulk heterojunction (BHJ) composites requires the investigation of three separate aspects and fundamental topics of organic semiconductors and photovoltaics.1. Synthesis: The project will start with available polymers for the transport matrix as well as for the sensitizers, and then quickly move over to novel polymers, customized for the purpose of near IR sensitizing, i.e. with various bandgap and smaller variations in the HOMO position.2. Morphology: The morphology assessment and morphology control of ternary BHJ composites will be another challenge in this project. Polymers which are not completely miscible to each other (and that is the common situation) will show demixing in solution as well as in the solid state. Following Hildebrandt, polymers are miscible to each other if they have comparable intermolecular adhesion forces. Our access to understand and investigate the phase separation mechanisms in ternary systems will be based on an approach similar to Hansen theory. By assessing the solubility parameters for the individual components we investigate the Hansen sphere for a ternary composite.3. Transport and Charge Transfer: Transport in binary BHJ composites is already a complex process. Within this project we will investigate the transport mechanisms in ternary composites. Specifically, we will explore suitable experimental methods which allow to distinguish between the role of the two polymer and their individual contributions to the hole transport. As important as transport is the charge generation process in the ternary blends. Time resolved pump-probe spectroscopy in the ns regime will be used to understand how the two polymers interact with each other. Most importantly, we want to clarify whether the two polymers may show direct charge transfer, energy transfer, or even have no electronic interactions.