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Spectroscopic study of excitations in pi-conjugated polymers.

机译：π共轭聚合物中激发的光谱研究。

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摘要

This dissertation deals with spin-physics of photo excitations in pi-conjugated polymers. Optical and magneto-optical spectroscopies, including continuous wave and time-resolved photo-induced absorption, photoluminescence, electroluminescence, and their optically detected magnetic resonance, were used to study steady state and transient photogeneration, energy transfer, spin relaxation, and spin dependent recombination process in the time domain from tens of nanoseconds to tens of milliseconds in polymer materials including regio-random poly (3-hexyl-thiophene-2,5-diyl), regio-regular poly (3-hexyl-thiophene-2,5-diyl), poly (9,9-dioctyl-fluorenyl-2,7-diyl), poly (poly (2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) of various morphologies, and transition metal complex poly (Pt-quinoxene).; Our studies provided the tools to clarify the physical pictures regarding two types of long-lived photoexcitations, namely polarons (both germinate polaron-pairs, and unpaired polarons) and triplet excitons, which are the major excitations in these exotic semiconductors in electrical and optical related applications.; From measurements of transient fluorescence and transient fluorescence detected magnetic resonance we show that photogenerated geminate polaron pairs live up to hundreds of microseconds following laser pulsed excitation. This conclusion is in agreement with the delayed formation of triplet excitons that we measured by transient photoinduced absorption. It also agrees with the weak spin-lattice relaxation rate in polymers that we measured using the optically detected magnetic resonance dynamic in thin films and organic light emitting devices.; Randomly captured nongeminate polaron pairs were shown to be the major source of optically detected magnetic resonance signal at steady, state. We found that the dynamics and magnitude of the signal depend on the spin-relaxation rate, generation rate and decay rate of the geminate pairs and nongeminate pairs. Importantly we found that the spin-relaxation rate depends weakly on temperature and strongly on coupled heavy atom orbital and magnetic momentum dipole induced by dopants or high intensity excitation. Also the polaron generation rate is excitation energy and nano-morphology dependent; whereas the polaron decay rate is morphology and spin dependent.
机译：本文研究了π共轭聚合物中光激发的自旋物理学。光学和磁光光谱学，包括连续波和时间分辨的光致吸收，光致发光，电致发光及其光学检测的磁共振，被用于研究稳态和瞬态光生，能量转移，自旋弛豫和自旋依赖性复合聚合物材料，包括区域随机聚（3-己基噻吩-2,5-二基），区域规则聚（3-己基噻吩-2,5-），在数十纳秒至数十毫秒的时域内发生变化二基），聚（9,9-二辛基芴基-2,7-二基），聚（各种形态的聚（2-甲氧基-5-（2-乙基己氧基）-1,4-亚苯基亚乙烯基）和过渡金属复杂的聚（Pt-喹喔啉）。;我们的研究提供了澄清两种长寿命光激发的物理图像的工具，这些激发是极化子（发芽极化子对和未配对极化子）和三重态激子，这是主要的激发在电子中这些奇异的半导体中与光学相关的应用。通过对瞬态荧光和瞬态荧光检测到的磁共振的测量，我们显示了光生化的双极化子对在激光脉冲激发后的寿命高达数百微秒。这个结论与我们通过瞬时光诱导吸收测量的三重态激子的延迟形成是一致的。这也与我们使用光学检测到的薄膜和有机发光器件中的磁共振动力学测量的聚合物中的弱自旋晶格弛豫速率相吻合。随机捕获的非对偶极化子对显示为稳定状态下光学检测到的磁共振信号的主要来源。我们发现信号的动力学和幅度取决于双子对和非双子对的自旋松弛率，生成率和衰减率。重要的是，我们发现自旋弛豫速率在很小程度上取决于温度，而在很大程度上取决于掺杂剂或高强度激发引起的重原子轨道和磁动量偶极耦合。极化子的产生速率也取决于激发能和纳米形态。而极化子的衰减速率是形态和自旋相关的。

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  • 作者

    Yang, Cungeng.;

  • 作者单位

    The University of Utah.;

  • 授予单位 The University of Utah.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 136 p.
  • 总页数 136
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 O49;
  • 关键词

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