Exploration of Ultrafast Carrier Dynamics In Polymer Semiconductors Using Terahertz Spectroscopy

0070285摩西亚皮秒时间尺度下共轭聚合物中的载流子动力学通常是未知的。太赫兹（THz）光谱的最新发展为这一时间范围内的载流子输运开辟了一个新的窗口。迄今为止，这种技术主要应用于“传统”半导体。本计画将利用此强有力的实验探针来研究各种共轭聚合物中的载子动力学。这项探索性研究的目标集中在选定的几个目前开放的问题。将进行三项研究。首先，将研究在载流子占据扩展态时，以及在显著的载流子捕获和复合发生之前，光激发后的电荷输运。其次，将进行研究如何链间耦合的强度修改的载流子输运探索PPV及其各种衍生物的运输，第三，孤子动力学在聚乙炔在高偏置场将进行研究。在这种情况下，理论上预测孤子速度达到一个平台，一个预测尚未得到验证。传输测量是基于电磁辐射的基本过程，通常在太赫兹范围内，由感应瞬态光电流发射。监测太赫兹信号的时间演化提供了关于0.1至10 ps时间尺度内的瞬态光电导的信息。这项研究采用了最先进的实验技术。研究生和博士后研究人员将参与这项研究，从而获得当代凝聚态物理和材料科学前沿领域的最新知识和技能。在发现半导体聚合物作为用于发光二极管（LED）和激光器的有前途的材料之后，在全世界范围内出现了积极的研究努力，以追求实现基于共轭聚合物的“塑料”激光器、LED和快速光检测器器件的目标。本计画主要研究准一维聚合物半导体在光激发后的发光过程的性质。这些过程发生在超快的时间尺度和他们的研究，现在有可能在实验超快光谱学的新发展。该项目涉及使用这些新技术定量研究各种聚合物材料光激发后超快发光过程的性质。这项研究将在学生和博士后研究人员的协助下进行，他们将获得凝聚态物理和材料科学当代前沿领域的技能和知识。***

0070285MosesThe carrier dynamics in conjugated polymers in the sub-picosecond time scale are generally unknown. Recent developments in terahertz (THz) spectroscopy have opened a new window to the carrier transport in this time regime. This technique has so far been applied mostly to "conventional" semiconductors. In this project advantage will be taken of this powerful experimental probe in using it to study the carrier dynamics in various conjugated polymers. The goals of this exploratory research are focused on a selected few currently open questions. Three studies will be undertaken. Firstly, the charge transport promptly following photoexcitations will be studied while the carriers occupy extended states, and before significant carrier trapping and recombination can occur. Secondly, a study will be performed on how the strength of the inter-chain coupling modifies the carrier transport by exploring the transport in PPV and its various derivatives, and thirdly, the soliton dynamics in polyacetylene at high bias fields will be studied. In this case the soliton velocity is predicted theoretically to reach a plateau, a prediction that has yet not been verified. The transport measurement is based on the fundamental process of electromagnetic radiation, typically in the THz range, emitted by the induced transient photocurrent. Monitoring the time-evolution of the THz signal provides information regarding the transient photoconductivity in the 0.1 to 10 ps time scale. This research employs state-of-the-art experimental techniques. Graduate students and post doctoral research associates will participate in this research and thereby acquire up-to-date- knowledge and skills in a forefront area of contemporary condensed matter physics and materials science.%%% Following the discovery of semiconductor polymers as promising materials for light emitting diodes (LEDs) and lasers, an active research effort has emerged worldwide in pursuit of the goal of realizing "plastic" lasers, LEDs, and fast photo-detector devices based on conjugated polymers. This project is concerned with the investigation of several unsolved questions concerning the nature of the light emission process in quasi-one dimensional polymer semiconductors promptly following photoexcitation. These processes occur at ultrafast time scales and their studies are now made possible by new developments in experimental ultrafast spectroscopy. This project is concerned with using these new techniques in the quantitative study of the nature of the processes that underlie the ultrafast emission of light following photoexcitation of various polymer materials. This research will be conducted with the assistance of students and post doctoral research associates who will thereby acquire skills and knowledge in a contemporary forefront area of condensed matter physics and materials science. ***