Andrew M. Rappe, Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania
200 Institute of Data Science
Halide perovskites have attracted a high and sustained level of scientific and applied interest for solar photovoltaics because they demonstrate long carrier lifetimes, high mobility, and high power conversion efficiency. The most effective materials incorporate molecular cations on the perovskite A site, making them “hybrid” halide perovskites, but both hybrid and inorganic halide perovskites offer impressive optoelectronic properties and pose strong scientific challenges. Despite the promise, the perovskites face multiple challenges before industrial insertion, including hysteresis and stability issues.
In this talk, I will report on key insights gleaned from theory and modeling to understand the novel couplings between mechanical, electronic, and optical responses in this class of materials. The low energy scale for vibrations and strains necessitates their explicit incorporation in electronic and optical calculations. I will present a multi-scale approach incorporating spin-orbit Hamiltonian terms, vibrational motions, thermal disorder, first-principles modeling, tight binding, molecular dynamics, and kinetic Monte Carlo. This comprehensive scheme brings a new understanding of ionic dynamics revealing emergent anharmonicity, electron-phonon coupling variations, and carrier transport and stability.
Andrew M. Rappe is a 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. 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 200 peer-reviewed articles on ferroelectric phase transitions in oxides, surface chemistry and catalysis of complex oxides, the theory of hybrid organic-inorganic perovskites, and topological materials.