CAREER: Controlling the Morphology of Polymer/Fullerene Solar Cells

技术概述：本研究计划的目的是确定控制聚合物/富勒烯太阳能电池光电功能的关键形态参数。聚合物基太阳能电池中的活性层通常是通过阻止聚合物/富勒烯共混物的相分离来制备的。这种非平衡过程形成的结构难以控制和精确表征，因此很难理解膜形态对器件效率的影响。该奖项将开发三个综合任务，分别研究畴大小、界面面积和聚合物结晶度对电荷产生、重组和传输过程的影响。首先，利用电子束图案化技术制备导电聚合物纳米结构。这些纳米结构具有耐溶剂性和热稳定性，并且诸如纳米结构几何形状、聚合物结晶度和聚合物交联密度等变量都是可调的。其次，利用已建立的光谱和器件表征技术对模型纳米结构/富勒烯太阳能电池的光电性能进行了评估。最后，通过对x射线散射数据的详细分析，精确地定量了畴尺寸、界面面积和结晶度。这项工作的一个特别重点是界面工程：假设聚合物/富勒烯界面组成曲线可以通过聚合物交联密度（除了退火温度和时间）来控制，为研究界面对电荷产生和损失的影响提供了一个简单的途径。通过这些系统研究获得的知识将确定基准聚合物/富勒烯体系的最佳设计属性，并指导各种高性能材料的形态优化。非技术总结：聚合物基太阳能电池有望实现低成本的太阳能转换，但在功率输出得到改善之前，该技术还不能作为一种替代能源。本研究计划通过建立一个系统来研究有源层结构与电子功能之间的关系，从而促进这些改进。这些发现将有助于优化聚合物基太阳能电池的效率。教育和外展活动以四种方式与本研究计划相结合。首先，PI鼓励高中生、本科生和研究生参与各种各样的研究，并参与许多K-12推广项目，向科学和工程领域代表性不足的群体介绍聚合物科学。其次，学生将通过新的纳米制造课程和多机构研讨会，教授x射线散射的基础知识，掌握多学科研究的必要技能。第三，通过与休斯敦当地材料行业的联系，学生将了解用于能量转换和储存的聚合物的商业化。最后，为了提高学生参与者的全球意识，PI将与韩国科学技术院（Korea Advanced Institute of Science and Technology）协调互补研究合作。

TECHNICAL SUMMARY: The objective of this research program is to identify the critical morphological parameters that control optoelectronic function in polymer/fullerene solar cells. The active layer in polymer-based solar cells is usually prepared by arresting the phase separation of a polymer/fullerene blend. The structures formed with this non-equilibrium process are difficult to control and accurately characterize, so it is hard to understand how film morphology influences the device efficiency. This award will develop three integrated tasks to investigate the effects of domain size, interfacial area and polymer crystallinity on charge generation, recombination, and transport processes, respectively. First, conductive polymer nanostructures are prepared by electron-beam patterning. These nanostructures are solvent-resistant and thermally-stable, and variables such as nanostructure geometry, polymer crystallinity, and polymer cross-link density are all tunable. Second, the optoelectronic performance of model nanostructure/fullerene solar cells is evaluated with established spectroscopic and device characterization techniques. Last, domain size, interfacial area, and crystallinity are accurately quantified with detailed analysis of X-ray scattering data. A particular focus of this work is interfacial engineering: It is hypothesized that polymer/fullerene interfacial composition profiles can be controlled through polymer cross-link density (in addition to annealing temperature and time), offering a simple route to study the effects of interfaces on charge generation and losses. The knowledge acquired through these systematic studies will identify the optimal design attributes for a benchmark polymer/fullerene system and guide morphology optimization for a variety of high-performance materials. NON-TECHNICAL SUMMARY: Polymer-based solar cells show promise for low-cost solar energy conversion, but the technology will not be viable as an alternative source of energy until the power output is improved. This research program facilitates those improvements by establishing a system to study the relationships between active layer structure and electronic function. These findings will help optimize the efficiency of polymer-based solar cells. Education and outreach activities are integrated with this research program in four ways. First, the PI encourages research participation for a diverse pool of high school, undergraduate and graduate students, and participates in numerous K-12 outreach programs that introduce polymer science to under-represented groups in science and engineering. Second, students will be equipped with the necessary skills for multidisciplinary research through a new nanofabrication course and a multi-institutional workshop that will teach the fundamentals of X-ray scattering. Third, through connections to the local Houston materials industry, students will learn about commercialization of polymers for energy conversion and storage. Finally, to enhance the global awareness of student participants, the PI will coordinate complementary research collaborations with the Korea Advanced Institute of Science and Technology.