Measuring the Dynamics of Excitons in 1D Semiconductor Quantum Wires with Quantum State Resolution

用量子态分辨率测量一维半导体量子线中激子的动力学

• 批准号: 1905751
• 负责人: Richard Loomis
• 金额: $ 45万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1905751&HistoricalAwards=false
• 关键词: Measuring; Dynamics; Excitons; 1D; Semiconductor

Nontechnical Description: In photovoltaic (PV) devices it would be ideal for every photon that impinges on the device to be absorbed and for at least one electron and one hole to be separately collected as current and electricity with little or no loss of energy within the system, regardless of the color of light or energy of the photon absorbed. PV devices that incorporate semiconductor nanoparticles (NPs) as the absorbing medium offer the advantages of tunable absorption energies through size control and large absorption efficiencies. When light with energy in excess of the band gap of the semiconductor NPs is absorbed, the photogenerated electrons and holes relax down to the lowest-energy states. The efficiency for the charge carrier relaxation depends on numerous factors, including the densities of electron and hole states, the roles and rates of different energy-transfer mechanisms, the temperature, and the chemical environment of the NPs. The research team is synthesizing NPs with varying sizes, shapes, semiconductor materials, and chemically passivated surfaces. Several optical spectroscopy and microscopy techniques are being implemented, and new models are being developed to characterize the relaxation dynamics in the semiconductor NPs. The ultimate goals of the research activities are to not only characterize the relaxation dynamics of the carriers, but to develop novel nanostructures with properties that are optimal for the light-to-electricity conversion of PV devices. The research project is highly interdisciplinary, and graduate and undergraduate students, especially those from underrepresented backgrounds, are gaining the expertise needed to become the next generation of scientists. The educational mission of the principal investigator extends beyond the research team as educational videos on the physics of light and on the importance of alternative energy sources are being developed and disseminated to the public and local schools.Technical Description: The relaxation dynamics and efficiencies of photogenerated electrons and holes in semiconductor nanoparticles (NPs) ultimately limit the yields of photovoltaic devices that incorporate NPs as the absorbing medium. The goals of the research are to accurately characterize the intraband relaxation dynamics (IRD) and mechanisms for carrier relaxation in semiconductor NPs. Specific research activities that include nanoparticle synthesis, electron microcopy and imaging, and optical spectroscopy in both the time- and frequency-domains are characterizing the IRD of the electrons and holes. The team is paying particular attention to the roles of dimensionality and the densities of states on the rates and efficiencies of electron and hole relaxation to the band edge. Carriers in one-dimensional semiconductor quantum wires (QWs) and belts (QBs) can have translational kinetic energy and delocalization along their lengths. This dimensionality gives rise to a continuum of states that can be accessed during carrier relaxation. These one-dimensional NPs contrast those of widely studied zero-dimensional quantum dot (QD) and two-dimensional quantum platelet (QP) systems. Time-resolved transient absorption experiments are performed on NPs with contrasting dimensionality to identify the role of the states, kinetic energy, and momentum on the carrier IRD. A new model, quantum-state renormalization is being developed to help unravel the dynamics from complicated transient absorption spectra recorded on ensembles of the NPs. The efforts are complemented through a long-standing collaboration with the synthetic group of William E. Buhro (Wash. U.) and a new collaboration with the ultrafast spectroscopy group of Martin Zanni (U. Wisconsin).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术描述：在光伏 (PV) 器件中，理想的情况是每个撞击到器件上的光子都被吸收，并且至少一个电子和一个空穴被单独收集为电流和电能，而在器件内几乎没有或没有能量损失。系统，无论光的颜色或吸收的光子的能量如何。采用半导体纳米颗粒（NP）作为吸收介质的光伏器件具有通过尺寸控制和高吸收效率可调节吸收能量的优点。当能量超过半导体纳米颗粒带隙的光被吸收时，光生电子和空穴弛豫到最低能态。载流子弛豫的效率取决于许多因素，包括电子和空穴态的密度、不同能量转移机制的作用和速率、温度和纳米粒子的化学环境。研究团队正在合成具有不同尺寸、形状、半导体材料和化学钝化表面的纳米粒子。几种光谱学和显微镜技术正在实施，并且正在开发新模型来表征半导体纳米颗粒的弛豫动力学。研究活动的最终目标不仅是表征载流子的弛豫动力学，而且是开发具有最适合光伏器件光电转换特性的新型纳米结构。该研究项目是高度跨学科的，研究生和本科生，尤其是那些来自弱势群体的学生，正在获得成为下一代科学家所需的专业知识。首席研究员的教育使命超出了研究团队的范围，因为正在开发有关光物理学和替代能源重要性的教育视频并向公立和当地学校传播。技术描述：光生的弛豫动力学和效率半导体纳米颗粒（NP）中的电子和空穴最终限制了采用纳米颗粒作为吸收介质的光伏器件的产量。该研究的目标是准确表征半导体纳米粒子中的带内弛豫动力学（IRD）和载流子弛豫机制。具体的研究活动包括纳米粒子合成、电子显微镜和成像以及时域和频域的光谱学，这些活动正在表征电子和空穴的 IRD。该团队特别关注维数和态密度对电子和空穴弛豫到能带边缘的速率和效率的作用。一维半导体量子线（QW）和带（QB）中的载流子可以具有平动动能和沿其长度的离域。这种维度产生了在载流子弛豫期间可以访问的连续状态。这些一维纳米粒子与广泛研究的零维量子点（QD）和二维量子片（QP）系统形成鲜明对比。在具有对比维度的纳米粒子上进行时间分辨瞬态吸收实验，以确定载流子 IRD 上的状态、动能和动量的作用。正在开发一种新模型，即量子态重整化，以帮助揭示纳米粒子系综上记录的复杂瞬态吸收光谱的动力学。通过与 William E. Buhro（华盛顿大学）的合成小组的长期合作以及与 Martin Zanni（威斯康星大学）的超快光谱小组的新合作，这些努力得到了补充。该奖项反映了 NSF 的法定使命和通过使用基金会的智力优点和更广泛的影响审查标准进行评估，该项目被认为值得支持。

项目成果

Excitation Energy Dependence of Photoluminescence Quantum Yields in Semiconductor Nanomaterials with Varying Dimensionalities

不同维度的半导体纳米材料中光致发光量子产率的激发能量依赖性

• DOI: 10.1021/acs.jpclett.0c00489
• 发表时间: 2020-05
• 期刊: The Journal of Physical Chemistry Letters
• 作者: Sanderson, William M.;Hoy, Jessica;Morrison, Calynn;Wang, Fudong;Wang, Yuanyuan;Morrison, Paul J.;Buhro, William E.;Loomis, Richard A.
• 通讯作者: Loomis, Richard A.

Bound-Ion Pair X-Type Ligation of Cadmium and Zinc Dithiocarbamates on Cadmium Selenide Quantum Belts

硒化镉量子带上二硫代氨基甲酸镉和二硫代氨基甲酸锌的束缚离子对 X 型连接

• DOI: 10.1021/acs.inorgchem.2c00226
• 发表时间: 2022-04
• 期刊: Inorganic Chemistry
• 影响因子: 4.6
• 作者: Meyer, Hailey M.;Morrison, Calynn E.;Loomis, Richard A.;Buhro, William E.
• 通讯作者: Buhro, William E.

Facet-Specific Electron Transfer in Pseudo-Two-Dimensional Wurtzite Cadmium Selenide Nanocrystals

伪二维纤锌矿硒化镉纳米晶体中的面特异性电子转移

• DOI: 10.1021/acs.jpcc.3c03825
• 发表时间: 2023-09-07
• 期刊: The Journal of Physical Chemistry C
• 作者: Hailey M. Meyer;Jie Chen;Richard A. Loomis;W. E. Buhro
• 通讯作者: W. E. Buhro

Photo-Induced State Shifting in 1D Semiconductor Quantum Wires

一维半导体量子线中的光致状态转移

• DOI: 10.1021/acs.jpcc.0c04755
• 发表时间: 2020-07
• 期刊: The Journal of Physical Chemistry C
• 作者: Sanderson, William M.;Schrier, Joshua;Loomis, Richard A.
• 通讯作者: Loomis, Richard A.

Intraband Relaxation Dynamics of Charge Carriers within CdTe Quantum Wires

CdTe 量子线内电荷载流子的带内弛豫动力学

• DOI: 10.1021/acs.jpclett.0c01326
• 发表时间: 2020-06
• 期刊: The Journal of Physical Chemistry Letters
• 作者: Sanderson, William M.;Wang, Fudong;Schrier, Joshua;Buhro, William E.;Loomis, Richard A.
• 通讯作者: Loomis, Richard A.