Single Molecule Scanning Tunneling Microscopy Studies of Dynamic Disorder in Organic Semiconductors

非技术描述：在平板显示器和太阳能电池等重要应用中使用有机电子材料的一个主要挑战是，这些材料通常缺乏良好的分子秩序。这种分子紊乱通常会导致许多基于有机物的器件性能受损。该项目解决了由于有机材料薄膜中分子的快速运动而产生的无序影响。研究小组使用了一种强大的显微镜，能够观察和分析单个分子的快速运动。通过在一系列重要的有机电子材料上进行这些实验，该项目为设备工程师提供了有关如何选择合适分子以最大限度地减少分子运动对设备性能的负面影响的信息。该项目支持研究生在有机电子学的许多方面的培训，并在跨学科有机和碳电子实验室的基础设施中发挥科学领导作用。该基础设施包括一个主要由本科生操作的材料制造设施。它还包括教育方面的倡议，如开发教学软件，以了解有机材料的原理。最后，该项目还支持小学生和中学生的晶体生长比赛。技术描述：在过去的十年中，动态无序已经成为了解有机电子材料性能基本限制的最前沿。位置和几何的波动——由声子和分子内振动介导——可以调节控制这些材料中电荷输运的电子传递积分。本课题利用变温扫描隧道显微镜中的隧道电流波动光谱，以单分子空间分辨率实时观察动态失序过程。通过调节样品温度，控制分子波动的时间尺度，并最终在低温下冻结。通过同时加入局部隧道光谱测量，隔离了轨道特定动力学效应。该项目重点研究最新的小分子有机电子材料，如侧臂功能化五苯和蒽噻吩。此外，它使用激光照射有机单晶，允许常规变温扫描隧道显微镜研究这些重要的材料类基准。

Nontechnical Description: A major challenge in the use of organic electronic materials in important applications like flat panel displays and solar cells is that these materials often lack good ordering of their molecules. Such molecular disorder often results in compromised performance of many organics-based devices. This project addresses the impact of disorder that arises from very fast motion of the molecules in thin films of organic materials. The research team uses a powerful microscope capable of observing and analyzing the rapid motion of single molecules. By carrying out these experiments on a range of important organic electronic materials, the project provides device engineers with information about how to choose appropriate molecules to minimize negative effects of molecular motion on device performance. The project supports training of graduate students in many aspects of organic electronics and scientific leadership within the infrastructure of the interdisciplinary Organic and Carbon Electronics Lab. This infrastructure includes a materials fabrication facility operated primarily by undergraduate students. It also includes educational initiatives such as the development of instructional software for understanding the principles of organic materials. Finally, the project also supports crystal growth competitions for grade and middle school students.Technical Description: In the past decade, dynamic disorder has come to the forefront of understanding of the fundamental limitations of performance in organic electronics materials. Fluctuations in position and geometry - mediated by phonons and intramolecular vibrations - can modulate electronic transfer integrals that control charge transport in these materials. This project applies tunneling current fluctuation spectroscopy in a variable temperature scanning tunneling microscope to observe dynamic disorder processes in real time with single molecule spatial resolution. By tuning sample temperature, the time scale of molecular fluctuations is controlled and eventually frozen out at low temperatures. By simultaneously adding local tunneling spectroscopy measurements, orbital specific dynamic effects are isolated. The project focuses on the newest classes of small molecule organic electronic materials such as side-arm functionalized pentacenes and anthradithiophenes. In addition, it uses laser illumination of organic single crystals to allow routine variable temperature scanning tunneling microscopy studies of these important materials class benchmarks.