Date: Tuesday, March 15, 2022
Time: 11:00 am
Talk Title: Hybrid Halide Perovskites: Highly Diverse and Tunable Semiconductors
Although known for many years, organic-inorganic (“hybrid”) perovskites have received extraordinary attention recently, because of the unique physical properties and chemical diversity offered by these structures, which make them outstanding candidates for applications in photovoltaic and other semiconductor devices. Perovskite crystal structures consist of networks of corner-sharing metal halide octahedra that extend in three or lower dimensions, interspersed with organic cations. The current presentation will explore several examples of the remarkable flexibility afforded by this unique semiconductor family (enabled in part by the mixing of organic and inorganic functionalities). As one example, selection of certain chiral organic cations in 2D perovskites may lead to a transfer of chirality between the organic and inorganic components and an associated breaking of symmetry within the inorganic layer, which in turn can provide a large Rashba-Dresselhaus splitting of the conduction band and associated control over spin texture . Alternatively, choice of organic cation has been shown to influence the melting temperature of hybrid perovskites by more than 100°C , enabling facile film melt-processing and the design of hybrid phase-change materials exhibiting glass-crystalline switching and associated modulation in optoelectronic properties . A third prospective topic involves semiconductor doping (effective control over carrier density/type), which underlies most successful device design and optimization. While generally challenging in halide perovskites, a recent study shows the use of the molecular dopant F4TCNQ as one pathway for effective control over carrier density in 3D perovskites . The above recent examples of tunability point to new opportunities for fundamental science and prospective device opportunities for these materials.
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David Mitzi received his B.S. in Electrical Engineering and Engineering Physics from Princeton University in 1985 and his Ph.D. in Applied Physics from Stanford University in 1990. Prior to joining the faculty at Duke in 2014, Dr. Mitzi spent 23 years at IBM’s T.J. Watson Research Center, where his focus was on the search for and application of new electronic materials, including organic-inorganic perovskites and inorganic materials for photovoltaic, LED, transistor and memory applications. For his final five years at IBM, he served as manager for the Photovoltaic Science and Technology Department, where he initiated and managed a multi-company program to develop a low-cost, high-throughput approach to deposit thin-film chalcogenide-based absorber layers for high-efficiency solar cells. Dr. Mitzi’s current research interests involve making emerging photovoltaic materials more effective, cost-efficient and competitive for the energy market. He holds a number of patents, and has authored or coauthored more than 200 papers and book chapters.