LDRD Seminar: Sept. 24, 2019
Named Fellow Peijun Guo (NST), Senior Physicist Jin Wang (XSD), and Senior Scientist Nestor Zaluzec (PSC) will discuss their Laboratory-Directed Research and Development (LDRD) sponsored work at the LDRD Seminar Series presentation Tuesday, Sept. 24, 2019, at 12:30 p.m. in Building 212, Room A157. All are welcome to attend.
Visit the LDRD website to view upcoming seminars.
“Strongly Anisotropic Excitons in Low-Dimensional Hybrid Perovskites,” by Peijun Guo (NST)
The need for exquisite control of light is ubiquitous in light-harvesting applications, optoelectronics, and information science. In this talk, I will discuss how hybrid materials such as low-dimensional organic-inorganic perovskites, which consist of distinct organic and inorganic sub-lattices, allow for dramatically enhanced light absorption and emission in the visible spectral range. Using a newly developed dielectric-coating based technique, we characterized the refractive index for these materials for the first time. We found that strong quantum confinement can be easily imparted to hybrid perovskites with the use of organic spacer-molecules, leading to a hyperbolic dispersion relation (i.e., the permittivity changes sign with direction). Such naturally occurring, exotic dispersion stems from the extremely anisotropic excitonic behaviors of low-dimensional perovskites and can intrinsically support a large photonic density of states, suggesting low-dimensional hybrid perovskites as excellent candidates for solid-state lighting applications.
Peijun Guo received his B.E. from Tsinghua University with highest honors in 2009, and his M.S. and Ph.D. from Northwestern University in 2011 and 2016, respectively, all in materials science and engineering. He is currently an Enrico Fermi Named Postdoc Fellow at Argonne National Laboratory. Guo has authored and co-authored more than 50 peer-reviewed journal publications and has been recognized with the Materials Research Society Graduate Student Gold Award and the SPIE Education Scholarship. His research is focused on the design and synthesis of inorganic and hybrid materials for enhanced light-matter interactions, and time-resolved optical studies of excited-state dynamics in complex material systems for energy conversion, optoelectronics, and information science.
“Developing Advanced Coherent Surface Scattering Reconstruction Method Based on Dynamical Scattering Theory,” by Jin Wang (XSD)
At the center stage of scientific topics ranging from energy production/storage to self-assembled hierarchical mesoscaled structures, surface/interface phenomena are of great interest to scientists in a variety of fields. Among surface probes, grazing-incidence X-ray scattering exhibits unique advantages for exploring the surface/interface problems that are challenging to solve. X-ray sources with brightness increased by a factor of 100 to 1000 will be achieved at the APS Upgrade (APS-U), which is well suited for measuring the spatiotemporal evolution of structures in complex systems with the highest precision. To take advantage of the new sources, coherent surface scattering imaging (CSSI) technique provides ideal tools to directly observe surface/interface structures and their dynamics responding to external stimuli. The implementation of a new beamline at the APS-U, dedicated to CSSI, requires a state-of-the-art coherent imaging reconstruction when conventional reconstruction methods are not sufficient. In this work, facilitated by high-performance computing resource at Argonne, we show a novel reconstruction method which incorporates dynamical scattering theory, required in the grazing-incidence condition, and enables CSSI to be a true 3D structural probe for the surface/interface visualization on mesoscales, at current and the future upgraded APS sources.
Jin Wang is a senior physicist in the X-ray Science division of the Advanced Photon Source, where he develops novel X-ray scattering and imaging techniques for applications ranging from time-resolved studies of fuel sprays to dynamics and structures of nanostructures.