2D Encapsulation of Molecular Crystals for Close-contact Measurement of Exciton Dynamics

用于激子动力学近距离接触测量的分子晶体二维封装

• 批准号: 1800187
• 负责人: Christopher Bardeen
• 金额: $ 42.6万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1800187&HistoricalAwards=false
• 关键词: 2D; Encapsulation; Molecular; Crystals; Close

Molecular crystals made from conjugated molecules are oftentimes called organic semiconductors. These materials can absorb light and efficiently transport the energy or excitation (called excitons), making them attractive for solar energy conversion applications. In addition, they support unique phenomena, such as the splitting of a single exciton into two lower-energy excitons, called singlet fission. In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Chris Bardeen of the University of California, Riverside is combining novel sample preparation with time-resolved optical microscopy to study excitons in organic crystals. The characterization of excitons in organic solids is challenging, since the fragile nature of the crystals makes it difficult to perform measurements. Professor Bardeen and his students overcome this challenge by encapsulating these crystals beneath two-dimensional sheets of graphene or hexagonal boron nitride. These atomically thin layers form an optically transparent and chemically-resistant coating for the crystal. The encapsulated crystals are then studied using high-resolution microscopy techniques that can follow the excitons as they move through the crystal and undergo singlet fission . Insights from the work could advance our understanding of light-emitting diodes and organic photovoltaic cells. The project is also exploring implications for fields such as quantum computing. The project is providing the graduate and undergraduate students involved in this research with advanced training in spectroscopy, materials characterization, microscopy, and data analysis, as well as supporting outreach efforts to Taft Elementary School. Ongoing projects include science demonstrations for various grades, science fair tutorials, a day-long visit to UCR by the fourth-grade, and classroom visits by undergraduate volunteers. A hands-on experiment for third graders has been developed in which each student builds a customized solar-powered car.The project focuses on prototypical molecular crystal semiconductors like perylene, tetracene ,and diphenylhexatriene. Plate-like molecular crystals with variable thicknesses are grown and then covered with graphene and hexagonal boron nitride. With this enabling technology in place, two categories of experiments are pursued. The first involves measuring the properties of the encapsulated crystal and its interaction with the environment using microscopy and photoluminescence methods. Questions that can be addressed include whether the exciton behavior in molecular crystals heterogeneous on length-scales down to 20 nm and whether it is possible to transfer energy and charge across the atomically thin membranes. The second category of experiments focuses on new space and time-resolved experiments to determine whether spin-entangled states of triplet pairs produced by singlet fission can extend over mesoscopic distances.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.

由共轭分子制成的分子晶体通常被称为有机半导体。这些材料可以吸收光并有效地传输能量或激发（称为激子），使它们对太阳能转换应用具有吸引力。 此外，它们支持独特的现象，例如单个激子分裂成两个较低能量的激子，称为单线态裂变。在这个由化学部化学结构动力学和机制（CSDM-A）计划资助的项目中，加州大学滨江分校的Chris Barnard教授将新型样品制备与时间分辨光学显微镜相结合，以研究有机晶体中的激子。 有机固体中激子的表征具有挑战性，因为晶体的脆弱性使得难以进行测量。 Barthel教授和他的学生通过将这些晶体封装在石墨烯或六方氮化硼的二维薄片下来克服这一挑战。这些原子级薄层形成晶体的光学透明和耐化学性涂层。然后使用高分辨率显微镜技术研究封装的晶体，该技术可以跟踪激子在晶体中移动并进行单线态裂变。这项工作的见解可以促进我们对发光二极管和有机光伏电池的理解。该项目还在探索对量子计算等领域的影响。该项目为参与这项研究的研究生和本科生提供光谱学、材料表征、显微镜和数据分析方面的高级培训，并支持塔夫脱小学的外展工作。正在进行的项目包括各年级的科学演示，科学公平的教程，为期一天的访问UCR的四年级，和课堂参观的本科志愿者。三年级学生的动手实验已经开发出来了，每个学生都制作了一辆定制的太阳能汽车，该项目的重点是原型分子晶体半导体，如二萘嵌苯，并四苯和二苯基己三烯。 生长具有可变厚度的板状分子晶体，然后用石墨烯和六方氮化硼覆盖。 有了这种使能技术，进行了两类实验。 第一个涉及测量封装晶体的性质及其与环境的相互作用，使用显微镜和光致发光方法。 可以解决的问题包括分子晶体中的激子行为在低至20纳米的长度尺度上是否不均匀，以及是否可以跨原子薄膜传输能量和电荷。 第二类实验侧重于新的空间和时间分辨实验，以确定由单重态裂变产生的三重态对的自旋纠缠态是否可以延伸到介观距离。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Hexagonal Boron Nitride Encapsulation of Organic Microcrystals and Energy-Transfer Dynamics

• DOI: 10.1021/acs.jpcc.0c06346
• 发表时间: 2020-08
• 期刊: Journal of Physical Chemistry C
• 影响因子: 3.7
• 作者: Wangxiang Li;Hao Tian;Jeremiah van Baren;Adam J. Berges;M. M. Altaiary-M.;Erfu Liu;E. Bekyarova;C. Lui;Jianlin Liu;C. Bardeen

Efficient Solid-State triplet-triplet annihilation up-conversion electroluminescence device by incorporating intermolecular intersystem-crossing dark sensitizer

• DOI: 10.1016/j.cej.2021.130889
• 发表时间: 2021-06-25
• 期刊: CHEMICAL ENGINEERING JOURNAL
• 影响因子: 15.1
• 作者: Chen, Chia-Hsun;Lin, Bo-Yen;Lee, Jiun-Haw
• 通讯作者: Lee, Jiun-Haw

Using sulfur bridge oxidation to control electronic coupling and photochemistry in covalent anthracene dimers

• DOI: 10.1039/c8sc05598j
• 发表时间: 2019-08-28
• 期刊: CHEMICAL SCIENCE
• 影响因子: 8.4
• 作者: Cruz, Chad D.;Yuan, Jennifer;Bardeen, Christopher J.
• 通讯作者: Bardeen, Christopher J.

Shaping Organic Microcrystals Using Focused Ion Beam Milling

• DOI: 10.1021/acs.cgd.9b01327
• 发表时间: 2020-03-01
• 期刊: CRYSTAL GROWTH & DESIGN
• 影响因子: 3.8
• 作者: Li, Wangxiang;van Baren, Jeremiah;Bardeen, Christopher J.
• 通讯作者: Bardeen, Christopher J.

Distinguishing between Triplet-Pair State and Excimer Emission in Singlet Fission Chromophores Using Mixed Thin Films

使用混合薄膜区分单线态裂变发色团中的三重态对状态和准分子发射

• DOI: 10.1021/acs.jpcc.1c09297
• 发表时间: 2022
• 期刊: The Journal of Physical Chemistry C
• 作者: Hausch, Julian;Berges, Adam J.;Zeiser, Clemens;Rammler, Tim;Morlok, Arne;Bredehöft, Jona;Hammer, Sebastian;Pflaum, Jens;Bardeen, Christopher J.;Broch, Katharina
• 通讯作者: Broch, Katharina