Overcoming Energy Loss in Organic Bulk Heterojunctions

成熟的太阳能技术，尤其是硅，正在美国越来越多的地方提供能源，其成本甚至远低于化石燃料。简而言之，作为一种低成本、清洁和无限可再生能源，太阳能正在兑现其60多年的承诺。然而，基于这种单一材料系统的所有太阳能解决方案仍然远远不是最佳解决方案。为了产生影响，新的解决方案必须以使太阳能发电无处不在为目标，最终满足我们不断扩大的能源需求。最近，有机光伏（opv）的急剧增加，导致了在含有新型非富勒烯受体（nfa）的电池中15%的太阳能转换效率（PCE）的演示，以及液体和溶液处理的有机和金属材料的不寻常组合，利用我们对纳米尺度非均相薄膜中电荷和激子传输的增加的理解。该研究的主要影响将是了解和改进opv，最终在成熟的太阳能技术效率较低的情况下提供超低成本的太阳能发电，例如太阳能发电窗口和建筑集成光伏发电，以及在非常低的光照水平下发电，以清除废弃的照明功率。该项目将支持在实验和材料设计与合成、光谱测量、数据采集和分析以及科学交流方面对不同群体的研究生和本科生进行教育。这些学院将寻求于2021年在密歇根大学举办一场物理学本科女性会议（CUWiP）。他们还将与当地少数民族服务机构建立牢固的联系，举办研讨会和简短讲座，讨论最先进的OPV设计和光谱测量。该项目将结合OPV设计和表征方面的广泛专业知识，以及最先进和新兴的多维相干光谱（MDCS），以了解目前限制单结OPV器件效率的能量损失机制。本研究旨在提高我们对基于nfa的opv的电荷和激发态输运机制以及能量损失来源的基本认识。这将通过开发和使用新的光谱和可视化工具来促进，这些工具可以精确地量化，在飞秒-秒的时间尺度上，从紫外到红外，光产生的电荷在异质界面上的转移和从它们的原点转移的动力学。从这些基础研究中得出的原理将提供分子设计规则来指导nfa基opv的改进，使其达到热力学限制的~25%的效率。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Mature solar technologies, in particular silicon, are now providing energy in a growing number of locales across the US at costs well below even that of fossil fuels. In short, solar energy is delivering on its promise of over 60 years as a source of low cost, clean and literally infinitely renewable energy. However, basing all solar solutions on this single materials system is still far from an optimal solution. To be impactful, new solutions must have the objective of making solar power generation a ubiquitous presence, ultimately filling all of our ever-expanding energy needs. Recently there have been dramatic increases in organic photovoltaics (OPVs) that have led to the demonstration of 15% solar power conversion efficiencies (PCE) in cells containing new non-fullerene acceptors (NFAs) and unusual combinations of liquid and solution-processed organic and metallic materials that leverage our increased understanding of charge and exciton transport in films with heterogeneous phases at the nanometer scale. The primary impact of the research will be to understand and improve OPVs to ultimately provide ultralow cost solar power in situations where established, mature solar technologies are less effective, such as in solar power generating windows and building-integrated photovoltaics, and generation at very low light levels to scavenge waste illumination power. The project will support the education of a diverse group of graduate and undergraduate students in experimental and material design and synthesis, spectroscopic measurement, data-taking and analysis, and scientific communication. The PIs will seek to host a Conference for Undergraduate Women in Physics (CUWiP) at the University of Michigan in 2021. They will also develop strong ties to local minority serving institutions to give seminars and short lectures discussing state of the art OPV design and spectroscopic measurements.The project will combine extensive expertise in OPV design and characterization with state-of-the-art and emerging multidimensional coherent spectroscopies (MDCS) to understand the energy loss mechanisms that currently limit single junction OPV device efficiencies. The research aims to improve our fundamental understanding of the mechanisms governing charge and excited state transport and sources of energy loss in NFA-based OPVs. This will be facilitated by the development and use of new spectroscopic and visualization tools that can precisely quantify, on femtosecond - second time scales across the UV and into the infrared, the dynamics of photogenerated charge transfer across heterogeneous interfaces and transport away from their points of origin. The principles derived from these fundamental studies will provide molecular design rules to guide the improvement of NFA-based OPVs towards their thermodynamically limited efficiencies of ~25%.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.