Professor Mercouri G. Kanatzidis

"Understanding perovskites: New materials for high efficiency all-solid-state solar cells"

About the Seminar

Liquid dye-sensitized solar cells (DSCs) are now rapidly giving way to solid-state devices. The removal of organic liquid electrolytes containing the I−/I3− redox couple, was achieved using perovskite materials. Using a novel inorganic material, CsSnI3, we have created new all-solid-state solar cells TiO2 based devices free of liquid electrolyte. This results set off an avalanche of new reports worldwide on the application of Pb-based perovskites in all solid state cells with rapid and spectacular advances in power conversion efficiency. Perovskite materials however are complex and they present challenges in stability, handling, processing etc. How much of this chemistry do we understand? Is it important to understand the chemistry at a fundamental level in order to make further progress? For example, CH3NH3PbI3 and CsSnI3 are unusual materials that undergo complex displacive and reconstructive phase transitions that affect their physical behavior. Tin based materials have even more potential in this field because they can replace the lead based systems, for which there are significant environmental toxicity concerns. The synthesis and chemistry of ASnI3 and APb1-xSnxI3 (A = CH3NH3+, HC(NH2)2+, etc) compounds will be presented. These materials consist of a 3D network and behave as medium band gap semiconductors (Eg = 1.20-1.40 eV) with octahedral metal coordination. The mobilities of carriers in these materials appear to be very high, and when doped the compounds also display significant electrical conductivity. This combination of properties renders the materials ideal for solar cell and other applications. Moreover, CH3NH3SnI3 exhibits intense room temperature photoluminescence at ~ 970nm and HC(NH2)2SnI3 at ~ 900 nm, a property that can be utilized in luminescent solar concentrators. All three properties strongly depend on the synthetic method and are very sensitive to Sn4+ doping level. Results on solar cells constructed from these materials will be presented.

About the Speaker

Mercouri Kanatzidis obtained a B. Sc degree in Chemistry from Aristotle University of Thessaloniki in Greece in 1979 and his Ph D. in Chemistry from the University of Iowa in 1984. He was a postdoctoral research fellow at the University of Michigan and Northwestern University from 1985 to 1987 and is currently Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern. Mercouri also holds an appointment at Argonne National Laboratory. His research interests are in the area of discovery as well as design and synthesis of advanced materials, nanostructures and large crystals. He is interested in thermal and solar energy conversion, radiation detection and superconductors for electronic, optoelectronic and direct power generation applications and also in environmental remediation. He is the recipient of the ACS Morley Medal; Alfred Sloan Research Fellowship; Richard Dreyfus Teacher-Scholar Award, NSF Presidential Young Investigator Award, Beckman Young Investigator Award, Guggenheim Fellow, and the International Thermoelectric Society Outstanding Achievement Award. He is a MRS and AAAS Fellow.