Photoexcitation Mechanisms and Transport Properties of Polarons and Solitons in Conjugated Polymers

本论文的研究重点是共轭聚合物中载流子的光生机理和载流子动力学。这些将通过两个实验进行研究：1。快速瞬态载流子密度测量在亚皮秒的时间制度，使用瞬态光诱导吸收探测在6-10？m光谱区域，其跨越由聚合物主链上的载流子产生的红外活性振动模式; 2.瞬态光电导测量前者测量将确定载流子量子效率对光子能量和链间耦合强度的依赖性，以及载流子复合动力学，而后者将探测载流子动力学。本研究的目的是研究共轭聚合物领域中的一些最基本的问题：孤子是主激发吗？孤子间相互作用的本质是什么？在高的孤子激发密度下，人们能跨越绝缘体-金属跃迁吗？在严格的一维系统中（例如，在单个聚合物链上）是否可能产生载流子？拟议的研究涉及国家的最先进的实验技术，因此将提供显着的教育效益，参与该项目的学生和博士后研究员。本研究利用瞬态载流子密度和瞬态光电导的测量方法，对各种共轭聚合物中载流子的光生机理和载流子动力学进行了研究。本研究的目的是研究共轭聚合物领域中的一些最基本的问题：孤子是主激发吗？孤子间相互作用的本质是什么？在高的孤子激发密度下，人们能跨越绝缘体-金属跃迁吗？在严格的一维系统中（例如，在单个聚合物链上）是否可能产生载流子？或者更确切地说，是固有的载体逃脱双生复合所需的链间耦合？如何通过修改链间耦合来影响载流子量子效率、载流子复合动力学和载流子输运？在载流子光激发过程中，中性激子的作用是什么？拟议中的研究将提供一种数据，应该结束这些核心问题。此外，拟议的研究涉及国家的最先进的实验技术，因此将提供显着的教育效益的学生和博士后研究所聚合物和有机固体在加州大学圣巴巴拉。

The proposed research is focused on the carrier photogeneration mechanism as well as the carrier dynamics in conjugated polymers. These will be investigated by means of two experiments: 1. Fast transient carrier density measurements in the sub-picosecond time regime, using transient photoinduced absorption probed in the 6-10 ?m spectral region, which spans the infrared active vibrational modes that arise from carriers on the polymer backbone; 2. transient photoconductivity measurements. The former measurement will determine the dependence of the carrier quantum efficiency on photon energy and interchain coupling strength, as well as carrier recombination dynamics, while the latter one will probe the carrier dynamics. The goal of this research is to investigate some of the most fundamental questions in the field of conjugated polymers: Are solitons primary excitations? What is the nature of soliton-soliton interaction? Can one cross the insulator-metal transition at high soliton excitation densities? Is carrier generation possible in strictly one-dimensional systems (e.g. on a single polymer chain)? The proposed research involves state-of-the-art experimental techniques, and thus will provide significant educational benefit to the students and post-doctoral fellows involved in the project. %%%This research is focused on the carrier photogeneration mechanism and carrier dynamics in various conjugated polymers by means of transient carrier density as well as transient photoconductivity measurements. The goal of this research is to investigate some of the most fundamental questions in the field of conjugated polymers: Are solitons primary excitations? What is the nature of soliton-soliton interaction? Can one cross the insulator-metal transition at high soliton excitation densities? Is carrier generation possible in strictly one-dimensional systems (e.g. on a single polymer chain)? Or rather, is interchain coupling inherently required for carriers to escape geminate recombination? How are the carrier quantum efficiency, carrier recombination dynamics, and carrier transport affected by modifying the inter-chain coupling? What is the role of neutral excitons in the carrier photoexcitation process? The proposed research will provide the kind of data that should bring a closure to these core questions. Additionally, the proposed research involves state-of-the-art experimental techniques, and thus will provide significant educational benefit to the students and post-doctoral fellows in the Institute for Polymers and Organic Solids at UC Santa Barbara.