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

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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.