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德克萨斯农工大学的孙东教授和阿列克谢·阿基莫夫博士研究卤化铅钙钛矿纳米晶体的新的光物理性质。卤化铅钙钛矿是一种新兴的半导体材料，在光子学和光催化等领域具有重要的应用。了解卤化铅钙钛矿的光物理性质，特别是那些以纳米晶体形式存在的性质，对于开发高性能太阳能电池和发光设备至关重要。孙教授的研究团队研究了一种名为量子限制的特殊条件下的光物理性质。这种量子限制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。这一条件可能会带来新的光学和电学性质，可用于构建高性能的光子和光催化器件。卤化铅钙钛矿的纳米晶形式还可以产生光子和电荷发射体等新功能，这些功能是从块状钙钛矿中无法获得的。由于很难在这些材料中实现可控的量子限制，这一领域的研究普遍具有挑战性。孙教授的团队探索了通过精确控制这些纳米材料的大小和形状来获取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之外，该项目还帮助学生利用自学硬件包对学生进行科学仪器和测量方面的培训，供学生进行深入学习体验。孙教授的团队还通过大学举办的开放日活动和公开讲座系列活动，接触到K-12学生和当地社区，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，孙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的光物理性质。预期的光物理性质可以使这些材料发展成为光子和电荷的来源，具有增强的能力，对于构建高性能的光子和光催化器件至关重要。该研究小组利用他们最近在制备高度均匀和强烈量子受限的卤化铅钙钛矿纳米晶方面的成功。这些材料增强了激子和其他自由度之间的耦合，这些自由度对于开辟新的光子和电荷产生途径至关重要。在这个项目中，孙教授的团队专门研究了低温下强烈受限的钙钛矿纳米晶体长寿命暗激子的稳定和强烈发射。该团队还研究了掺杂锰的卤化铅钙钛矿纳米片的增感作用，得益于巨型振子强度激子跃迁和长寿命暗激子向锰的有效能量转移。此外，还阐明了通过激子到热电子上转换在掺锰钙钛矿量子点中增强热电子产生和热电子光电子发射等过程。这一奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的智力优势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.