报告摘要

With limited supply of fossil fuels and their adverse effect on the environment, finding materials to harvest and store clean energy is one of the greatest challenges in the 21st century.  Solar energy is an ideal renewable source, but its harvesting and storage requires efficient, cost-effective, and environmentally friendly materials for solar cells and batteries. This talk will focus on one class of such materials1-6 based on perovskites. Hybrid perovskites composed of organic cations and inorganic anions have emerged in the past few years as the next generation solar cells with power conversion efficiency reaching above 20%. However, the instability of these materials when exposed to moisture, is one of the most challenging problems.  Using density functional theory and molecular dynamics simulation, we have analyzed the source of this instability and show how this can be overcome by replacing halogens with cluster ions, without compromising their electronic or optical properties. These cluster ions mimic the chemistry of halogens and have electron affinities that are either similar or greater than those of halogens. Similarly, antiperovskites which have been recently used as solid electrolytes in Li-ion batteries can be modified to increase their superionic conductivity. This is achieved by replacing alkali atoms with superalkali ions and halogens with superhalogens. Examples of water-resistant hybrid perovskites for solar cells and anti- perovskites for superionic conductors include MAPbI2.75(ph)0.25 (ph = SCN, SeCN, PCO, OCl, OBr and OI), and Li3S(BF4)0.5Cl0.5, respectively. Much of the science in these materials can be understood by visualizing these modified perovskites as super-alkali halides where alkali cations and halogens anions are replaced by respective super-ions. A new class of solids with clusters as building blocks can usher a new era in materials science where rational design can lead to materials with unprecedented properties.
 
报告人简介：

Puru Jena, Distinguished Professor of Physics at Virginia Commonwealth University (VCU) received his Ph. D. at the University of California. He joined VCU in 1980 and has been there ever since, with the exception of two years when he was a program director at the National Science Foundation and Jefferson Science Fellow and senior science adviser at the US Department of State. Dr. Jena’s research covers a wide range of topics in condensed matter physics and nano-science dealing with the structure-property relationships of matter, such as atomic clusters, cluster-assembled materials, super-ion inspired materials for energy storage and conversion, superatoms as building block of a three-dimensional periodic table, and hydrogen storage materials. He is the author of nearly 600 papers and 13 edited books. Dr. Jena’s honors include: Outstanding Scientist of Virginia, Presidential Medallion from VCU, Fellow of the American Physical Society, Outstanding Faculty Award from the State Council of Higher Education of Virginia, and Award of Excellence and Outstanding Scholar Award from VCU, and co-chair of the Presidential Commission on bilateral scientific collaboration between USA and Russia.

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