Imaging Defect Dynamics in Organic Semiconductor Films

技术说明：本研究项目的目标是应用新型扫描探针显微镜工具来了解局部结构和无序如何影响有机半导体薄膜的光化学稳定性和电荷转移态的形成。 为了实现这一目标，该项目使用新的实验能力，如时间分辨静电力显微镜，使局部结构无序和局部变化之间的直接纳米级相关性的光化学陷阱的形成，掺杂和界面电荷转移状态能量。这些观察结果可以为我们理解结构和加工如何影响有机半导体的光化学和光物理学以及光电二极管和光电子学的技术影响提供独特的视角。该项目解决了与总体目标相关的三个挑战：（1）使用亚微秒时间分辨静电力显微镜方法研究异质性和局部无序对最先进的高效有机体异质结光化学降解的作用;（2）理解局域结构和无序对局域载流子输运、光化学掺杂、以及使用非接触能量耗散的这些光化学过程的时间演变（质量因子）测量;以及（3）以空间和光谱分辨的方式理解形态和结构异质性对电荷转移状态的能量分布的作用。有机半导体目前用于电子显示器中，并且对于用作轻质、低成本的太阳能电池（例如为消费电子产品供电和充电，或最终为电网收集太阳能）是有兴趣的。长期稳定性是这些应用的一个主要挑战，该项目旨在通过应用新开发的扫描探针显微镜工具，更好地了解这些材料在数十纳米的非常精细的长度尺度上如何形成缺陷和缺陷的细节。有机半导体在照明和太阳能中的可能应用不仅具有显著的直接经济和社会影响，而且可以成为吸引学生和更广泛公众参与科学教育的宝贵手段。该项目的外展部分开发了新的数字和视觉媒体，用于大规模的公众参与，接触K-12学生和当地社区。除了在化学，物理和材料科学的接口培训研究生外，该项目还直接支持本科生研究，并通过与雷尼尔学者计划建立新的合作伙伴关系来解决科学教育管道问题。

Technical Description: The goal of this research project is to apply novel scanning probe microscopy tools to understand how local structure and disorder influence photochemical stability and charge transfer state formation in organic semiconductor films. To accomplish this goal, the project uses new experimental capabilities such as time-resolved electrostatic force microscopy to make direct nanoscale correlations between local structural disorder and local variations in photochemical trap formation, doping, and interfacial charge transfer state energies. These observations can add a unique perspective to our understanding of how structure and processing affect the photochemistry and photophysics of organic semiconductors with technological implications for photodiodes and photovoltaics. The project tackles three challenges related to the overall goal: (1) using sub-microsecond time-resolved electrostatic force microscopy methods to study the role of heterogeneity and local disorder on the photochemical degradation of state-of-the art high-efficiency organic bulk heterojunctions; (2) understanding the role of local structure and disorder on local carrier transport, photochemical doping, and the evolution of these photochemical processes in time using non-contact energy dissipation (quality factor) measurements; and (3) understanding the role of morphology and structural heterogeneity on the energetic distribution of charge transfer states in a spatially and spectrally resolved fashion.Non-Technical Description: Organic semiconductors are currently used in electronic displays, and are of interest for use as light-weight, low-cost solar cells (for instance to power and recharge consumer electronics, or eventually harvest solar energy for the grid). Long term stability is a major challenge for these applications, and this project seeks to better understand the details of how imperfections and defects form in these materials at very fine length scales of tens of nanometers through the application of newly developed scanning-probe microscopy tools. The possible applications of organic semiconductors in lighting and solar energy not only have significant direct economic and societal impact, but can be valuable hooks for engaging students and the broader public in science education. The outreach component of the project develops new digital and visual media for large scale public engagements reaching K-12 students and the local community. In addition to training graduate students at the interface of chemistry, physics, and materials science, the project directly supports undergraduate research and seeks to address science education pipeline issues by beginning a new partnership with the Rainier Scholars program.