Tailored Light-Matter Interactions in Scalable and Artificial Nanomaterials

Peijun Guo, Ph.D.
Argonne National Laboratory

The need for exquisite control of light is ubiquitous in energy-relevant applications, optoelectronics, and information science. In this talk, I will discuss how hybrid materials consisting of distinct sub-lattices and periodically nanostructured materials allow for dramatically enhanced light scattering, absorption, emission and charge carrier collection at various time- and length-scales. I will first focus on hybrid organic-inorganic perovskites. These solution-processed, scalable materials exhibit remarkable optoelectronic properties such as strong light absorption, defect tolerance, and long carrier lifetimes. I will describe how electronic excitations in these materials are coupled to and influenced by the vibrational degrees of freedom of the organic and inorganic sublattices, investigated using an array of optical spectroscopic techniques. The unique soft nature of the lead-halide octahedral framework gives rise to dynamic fluctuations in the electronic bandgap, which distinguishes hybrid perovskites from traditional inorganic semiconductors. Furthermore, strong quantum confinement can be easily imparted to hybrid perovskites with the use of organic spacer-molecules, leading to exotic dispersion relation and enhanced light-emitting properties. Beyond solution-processed semiconductors, I will demonstrate how widely-used materials, such as indium-tin-oxide (ITO), can be grown in ordered, nanoscale array form by chemical vapor phase epitaxy to exhibit well-defined localized surface plasmon resonances in the infrared spectral range. The unique band structure and carrier concentration of ITO result in an unusual type of optical nonlinearity that is significantly larger and faster than the noble metal counterparts, opening new avenues for ultrafast optical switching and active photonic devices.

About the Speaker

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. Dr. Guo has authored and coauthored 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 focuses 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.