Exciton and its Coupling with Spin and Lattice in Strongly Quantum Confined 0D-2D Lead Halide Perovskite Nanocrystals

化学系的大分子、超分子和纳米化学项目支持董H教授。Son和德克萨斯A M大学的Alexey Akimov博士研究了卤化铅钙钛矿纳米晶体的新物理性质。卤化铅钙钛矿是新兴的半导体材料，在光子学和微电子学中具有重要的应用。了解卤化铅钙钛矿的物理化学性质，特别是那些以纳米晶体形式存在的卤化铅钙钛矿，对于开发高性能太阳能电池和发光器件至关重要。孙教授的研究小组研究了在一种称为量子限制的特殊条件下的物理性质。这种量子限制的条件是通过使纳米晶体的尺寸和形状小于几纳米来实现的。这种条件可能会带来新的光学和电子特性，用于构建高性能的光子和光催化器件。不能从本体形式获得的新功能性也可以从卤化铅钙钛矿作为光子和电荷发射体的非晶形式中出现。由于在这些材料中实现可控量子限制的困难，这一领域的研究通常具有挑战性。Son教授的团队通过精确控制这些纳米材料的尺寸和形状，探索了获得有用的量子限制诱导特性的有效方法。除了科学活动和影响外，该项目还利用向学生提供的自学硬件包，为学生提供科学仪器和测量方面的培训，以获得深入的学习经验。 孙教授的团队还接触到K-12学生和当地社区，通过大学举办的开放式活动和公开讲座系列提供讲座和动手科学实验。 在化学系大分子，超分子和纳米化学项目的支持下，Son教授的研究团队通过0到2维的受控量子限制研究了卤化铅钙钛矿纳米晶体的新物理性质。 预期的光物理性质可以使这些材料能够发展成为光子和电荷的来源，具有对于构建高性能光子和光催化器件重要的增强能力。该研究小组利用他们最近在制备高度均匀和强量子限制的卤化铅钙钛矿纳米晶体方面的成功。 这些材料增强了激子和其他自由度之间的耦合，这些自由度对于打开光子和电荷产生的新途径至关重要。在这个项目中，Son教授的团队专门研究了在低温下强烈限制的钙钛矿纳米晶体的非常长寿命的暗激子的稳定和强烈的发射。 该团队还研究了Mn掺杂的卤化铅钙钛矿纳米片的增强敏化作用，这得益于巨振子强度激子跃迁和长寿命暗激子向Mn的有效能量转移。此外，还阐明了Mn掺杂钙钛矿量子点中通过激子到热电子上转换增强热电子产生和热电子光电发射等过程。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。

The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division supports Professor Dong H. Son and Dr. Alexey Akimov at Texas A&M University to investigate new photophysical properties of lead halide perovskite nanocrystals. Lead halide perovskites are newly emerging semiconductor materials important for various applications in photonics and photocatalysis. Understanding the photophysical properties of lead halide perovskites, particularly those found in nanosized crystal forms, is essential to developing high-performance solar cells and light emitting devices. Professor Son’s research team studies the photophysical properties under a special condition called quantum confinement. This condition of quantum confinement is achieved by making the nanocrystals’ size and shape smaller than several nanometers. This condition may bring about new optical and electronic properties useful for building high performance, photonic and photocatalytic devices. New functionalities, not obtainable from the bulk form, can also emerge from the nanocrystal forms of lead halide perovskites as photon and charge emitters. Research in this area has generally been challenging due to the difficulty in realizing controllable quantum confinement in these materials. Professor Son’s team explores effective ways of accessing the useful quantum confinement-induced properties by precisely controlling the size and shape of these nanomaterials. In addition to the scientific activities and impacts, this project contributes to student training on scientific instrumentation and measurements utilizing self-learning hardware kits checked out to students for in-depth learning experience. Professor Son’s team also reaches out to K-12 students and to the local community providing lectures and hands-on science experiments through University-run open-house events and a public lecture series. With this support from the Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division, Professor Son’s research team investigates new photophysical properties of lead halide perovskite nanocrystals via controlled quantum confinement in 0 to 2 dimensions. The anticipated photophysical properties can enable these materials to be developed into a source of photons and charges with enhanced capabilities important for building high-performance photonic and photocatalytic devices. The research team leverages their recent success in preparing highly uniform and strongly quantum confined lead halide perovskite nanocrystals. These materials enhance the coupling between exciton and other degrees of freedom crucial for opening new pathways of photon and charge generation. In this project, Professor Son’s team specifically examines the stable and intense emission from very long-lived dark excitons of the strongly confined perovskite nanocrystals at low temperatures. The team also investigates enhanced sensitization in Mn-doped lead halide perovskite nanoplatelets benefitting from the giant oscillator strength exciton transition and efficient energy transfer of long-lived dark exciton to Mn. In addition, processes such as enhanced hot electron generation and hot electron photoemission in Mn-doped perovskite quantum dots via exciton-to-hot electron upconversion are elucidated.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.