Understanding and Enhancing Electronic Coupling Between Metal Halide Perovskite Quantum Dots Through Surface Molecular Engineering

纳米颗粒是非常小的晶体。它们的尺寸可以只有几纳米，或者比一张纸薄大约10万纳米，它们可以由许多不同类型的材料制成，包括半导体。 当电子被挤压到非常小的半导体纳米晶体中时，它们会受到量子限制，并出现新的特性，这些特性可以用于新技术。在进行应用之前，研究人员必须学会如何将量子点（QD）组装成固体，以便一个纳米颗粒可以与另一个纳米颗粒共享电子。 在化学系高分子、超分子和纳米化学项目的支持下，金忠教授在北京大学化学系的高分子、超分子和纳米化学项目中担任了本课题的研究员。来自加州圣克鲁斯大学（UCSC）的张和袁平正在研究由一类称为钙钛矿的新型半导体形成的量子点固体。 与传统的半导体（如硅）不同，钙钛矿是无机成分和有机分子的混合物，这产生了不寻常的特性。 张教授和平教授正在与他们的学生合作，开发创造稳定的量子点固体的方法，在这种固体中，电子很容易被共享。 他们的发现可能会影响从量子计算到太阳能电池的应用。该项目还为未来的科学家提供先进实验和计算技术方面的培训机会。 通过每年夏天举办的“太阳、光谱学和圣克鲁斯”活动，研究小组向当地高中学生和教师介绍该项目，以提高公众对科学的认识。该研究小组正在开发基于金属卤化物（MH）钙钛矿的新型半导体QD固体。该研究解决了量子点固体的电荷传输特性通常由于量子点之间的弱耦合而受到限制的挑战，阻碍了新兴技术中的器件应用。该项目系统地研究了决定钙钛矿量子点（PQD）之间电子耦合的基本因素，如尺寸，形状和表面，通过开发设计师配体来增强PQD之间的耦合及其稳定性。PDQs之间的耦合和配体之间的相互作用，其特征在于使用时间分辨的光致发光，透射电子显微镜，红外光谱和超快泵浦-探测方法的组合。独特的导电或芳族配体分子预期既稳定QD又增强它们的电子耦合，使得QD固体将表现出强的电荷传输，同时保持QD的新颖性质。基于最先进的量子力学方法的计算研究正在探索配体-PQD相互作用和PQD间耦合，以指导和证实实验研究。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nanoparticles are extremely small crystals. They can be just a few nanometers in size, or about 100,000 thinner than a sheet of paper, and they can be formed from many different types of materials, including semiconductors. When the electrons are squeezed into very small semiconductor nanocrystals, they become quantum-confined and new properties emerge, which can be harnessed for use in new technologies. Before proceeding to applications, researchers must learn how to pack the quantum dots (QDs) together into solids so that one nanoparticle can share its electrons with another. With support from the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professors Jin Z. Zhang and Yuan Ping from University of California Santa Cruz (UCSC) are studying QD solids formed from a new class of semiconductors called perovskites. Unlike traditional semiconductors, such as silicon, perovskites are a mixture of inorganic components and organic molecules and this gives rise to unusual properties. Working with their students, Professors Zhang and Pin are developing ways to create stable QD solids where the electrons are easily shared. Their discoveries could impact applications ranging from quantum computing to solar cells. The project also provides training opportunities for future scientists in advanced experimental and computational techniques. Through their "The Sun, Spectroscopy, and Santa Cruz" events held each summer, the research groups are introducing the project to local high school students and teachers to enhance public awareness about science. The research team is developing novel semiconductor QD solids based on metal halide (MH) perovskites. This research addressws the challenge that charge transport properties of QD solids are often limited due to weak coupling between QDs, hindering device applications in emerging technologies. The project is systematically studying the fundamental factors, such as size, shape and surface, that determine the electronic coupling between perovskite QDs (PQDs) by developing designer ligands that enhance both the coupling between the PQDs and their stability. The coupling between PDQs and interaction between ligands are characterized using a combination of time-resolved photoluminescence, transmission electron microscopy, infrared spectroscopy, and ultrafast pump-probe methods. Unique conductive or aromatic ligand molecules are expected to both stabilize the QDs and enhance their electronic coupling so that the QD solids will exhibit strong charge transport while maintaining the novel properties of the QDs. Computational studies based on state-of-the-art quantum mechanical methods are exploring the ligand-PQD interaction and inter-PQD coupling to guide and corroborate experimental studies.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.