AEM Seminar: Theory and modeling of correlated ionic and electronic motions in hybrid organic-inorganic perovskites
Andrew Rappe, Blanchard Professor of Chemistry and Professor of Materials Science and Engineering, University of Pennsylvania
2:30 PM on 2017-10-06
100 Bell Museum *IMPORTANT NOTE: Although the Bell Museum's galleries are now closed (to reopen on the St. Paul campus in 2018), the Bell Auditorium (Room 100) is still open and is accessible through the side doors. Joint Seminar with ME and CTC.
The perovskite crystal structure hosts a wealth of intriguing properties, and the renaissance of interest in halide (and hybrid organic-inorganic) perovskites (HOIPs) has further broadened the palette of exciting physical phenomena. Breakthroughs in HOIP synthesis, characterization, and solar cell design have led to remarkable increases in reported photovoltaic efficiency.
However, the observed long carrier lifetime and PV performance have eluded comprehensive physical justification. The hybrid perovskites serve as an enigmatic crossroads of physics. Concepts from crystalline band theory, molecular physics, liquids, and phase transitions have been applied with some success, but the observations of HOIPs make it clear that none of these conceptual frameworks completely fits. In this talk, recent theoretical progress in understanding HOIPs will be reviewed and integrated with experimental findings. The large amplitude motions of HOIPs will be highlighted, including ionic diffusion, anharmonic phonons, and dynamic incipient order on various length and time scales. The intricate relationships between correlated structural fluctuations, polar order, and excited charge carrier dynamics will also be discussed.
Bio:
Andrew M. Rappe is Blanchard Professor of Chemistry and Professor of Materials Science and Engineering at the University of Pennsylvania. He received his A. B. in “Chemistry and Physics” summa cum laude from Harvard University in 1986, and his Ph. D. in “Physics and Chemistry” from MIT in 1992. He was an IBM Postdoctoral Fellow at UC Berkeley before starting at Penn in 1994.
Andrew received an NSF CAREER award in 1997, an Alfred P. Sloan Research Fellowship in 1998, and a Camille Dreyfus Teacher-Scholar Award in 1999. He was named a Fellow of the American Physical Society in 2006. He was awarded a Humboldt Research Award in 2017.
Andrew is one of the two founding co-directors of Pennergy: the Penn Center for Energy Innovation. He is also one of the founding co-directors of the VIPER honors program at Penn, the Vagelos Integrated Program in Energy Research.
Andrew has published more than 240 peer-reviewed articles. Many of his current research interests revolve around ferroelectric phase transitions in oxides, surface chemistry and catalysis of complex oxides, and the interplay between the two: a) He helped establish relationships between composition and ferroelectric phase transition temperature in bismuth-containing perovskite oxides, b) He predicted that changing chemical vapor composition above a ferroelectric oxide could reorient its polarization, c) He revealed the mechanism of domain wall motion in ferroelectric oxides, d) He showed that changing ferroelectric polarization dramatically changes catalytic activity of supported metal films and nanoparticles, and e) He uses computational materials design to invent new ferroelectric photovoltaics for solar applications. In recent years, he has become actively involved in the theory of hybrid organic-inorganic perovskites and topological materials.
Joint Seminar with Mechanical Engineering and the Chemical Theory Center.