Quantum State Resolved Spectroscopy of Excitonic and Multi-Excitonic Dynamics in Quantum Confined Nanostructures and Heterojunctions

量子约束纳米结构和异质结中激子和多激子动力学的量子态分辨光谱

• 批准号: 1206451
• 负责人: John Wright
• 金额: $ 46万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206451&HistoricalAwards=false
• 关键词: Quantum; State; Resolved; Spectroscopy; Excitonic

TECHNICAL SUMMARYMultiresonant Coherent Multidimensional Spectroscopy (CMDS) is a new and potentially transformative approach for characterizing complex nanostructures. It is based on using multiple tunable laser beams to excite different quantum states to form multiple quantum coherences (MQCs) that re-emit output beams during the time the MQCs retain their quantum mechanical phase coherence. This program, supported by the NSF Solid State and Materials Chemistry Program, uses the resonances with the quantum states to create multidimensional signatures of the individual substructures within complex nanostructures. It isolates the individual coherence pathways that contribute to the output intensity and uses these pathways to obtain the coherent and incoherent dynamics with quantum state resolution. The coherent dynamics includes both dephasing interactions and coherence transfer and the incoherent dynamics includes charge transfer and population relaxation. The program is particularly interested in developing methods for quantum state resolution of the charge transfer dynamics between donor-acceptor substructures within larger nanostructures. The quantum states of interest include the quantum confined excitonic and multiexcitonic states of the substructures as well as surface states. The multidimensional spectra and the coherent and incoherent dynamics of the multiexcitonic states identify the mechanisms responsible for multiexciton generation (MEG). Higher order wave mixing probes the potential energy surface of different energetic excitons. Alternative CMDS methodologies include 3-color pathways and multiplex detection. The nanostructures used in this program are simple, well-characterized model systems that represent the different quantum confined substructures and morphologies that are of interest in developing new nanotechnologies. NON-TECHNICAL SUMMARYProviding the energy required for the future is an enormous challenge that requires new technologies that efficiently harvest solar energy and turn it into the electrical power and solar fuels needed for growing economies. Nanotechnology is a promising direction for providing this capability because the quantum effects that occur at small dimensions provide opportunities for engineering complex nanostructures that are efficient and robust solar converters. The small size of these nanostructures dictates the creation of new technologies that can access the individual quantum states within the individual substructures and follow the flow of energy from the initial absorption of light to the final conversion into electricity or solar fuels. The laser methods developed in this program will provide these capabilities. Not only will this methodology define the fundamental scientific principles controlling how the energy is harvested and used but it will be disseminated to the wider scientific community through web site tutorials, scientific conferences and public lectures, on-line course materials, and the training of undergraduate and graduate students. The dissemination will be transformative because this new methodology provides deeper insights into how materials function and can address questions that cannot be answered by current technologies.

技术摘要多共振相干多维光谱 (CMDS) 是一种新的、具有潜在变革性的表征复杂纳米结构的方法。它基于使用多个可调谐激光束激发不同的量子态以形成多个量子相干性 (MQC)，在 MQC 保持其量子机械相位相干性期间重新发射输出光束。该项目由 NSF 固态和材料化学项目支持，利用量子态共振来创建复杂纳米结构内各个子结构的多维特征。它隔离了有助于输出强度的各个相干路径，并使用这些路径来获得具有量子态分辨率的相干和非相干动力学。相干动力学包括相干相互作用和相干转移，非相干动力学包括电荷转移和布居弛豫。该项目特别感兴趣的是开发较大纳米结构内供体-受体子结构之间电荷转移动力学的量子态分辨率方法。感兴趣的量子态包括子结构的量子限制激子态和多激子态以及表面态。多激子态的多维光谱以及相干和非相干动力学确定了多激子生成（MEG）的机制。高阶波混合探测不同高能激子的势能面。替代 CMDS 方法包括 3 色路径和多重检测。该程序中使用的纳米结构是简单、特征良好的模型系统，代表了开发新纳米技术感兴趣的不同量子限制子结构和形态。非技术摘要提供未来所需的能源是一项巨大的挑战，需要新技术来有效地收集太阳能并将其转化为经济增长所需的电力和太阳能燃料。纳米技术是提供这种能力的一个有前途的方向，因为小尺寸下发生的量子效应为设计复杂的纳米结构提供了机会，这些纳米结构是高效且稳健的太阳能转换器。这些纳米结构的小尺寸决定了新技术的创建，这些新技术可以访问各个子结构内的各个量子态，并跟踪从最初吸收光到最终转化为电力或太阳能燃料的能量流动。该计划中开发的激光方法将提供这些功能。这种方法不仅将定义控制如何收集和使用能量的基本科学原理，还将通过网站教程、科学会议和公开讲座、在线课程材料以及本科生培训向更广泛的科学界传播。和研究生。这种传播将具有变革性，因为这种新方法可以更深入地了解材料的功能，并可以解决当前技术无法回答的问题。