Structural Tolerance Factor Approach to Defect-Resistant I<inf>2</inf>-II-IV-X<inf>4</inf> Semiconductor Design

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Copyright © 2020 American Chemical Society. Recent work on quaternary semiconductors Cu2BaSn(S,Se)4 and Ag2BaSnSe4 for photovoltaic and thermoelectric applications, respectively, has shown the promise of exploring the broader family of defect-resistant I2-II-IV-X4 materials (where I, II, and IV refer to the formal oxidation state of the metal cations and X is a chalcogen anion) with tetrahedrally coordinated I/IV cations and larger II cations (i.e., Sr, Ba, Pb, and Eu) for optoelectronic and energy-related applications. Chemical dissimilarity among the II and I/IV atoms represents an important design motivation because it presents a barrier to antisite formation, which otherwise may act as electronically harmful defects. We herein show how all 31 experimentally reported I2-II-IV-X4 examples (with large II cations and tetrahedrally coordinated smaller I/IV cations), which form within five crystal structure types, are structurally linked. Based on these structural similarities, we derive a set of tolerance factors that serve as descriptors for phase stability within this family. Despite common usage in the well-studied perovskite system, Shannon ionic radii are found to be insufficient for predicting metal-chalcogen bond lengths, pointing to the need for experimentally derived correction factors as part of an empirically driven learning approach to structure prediction. We use the tolerance factors as a predictive tool and demonstrate that four new I2-II-IV-X4 compounds, Ag2BaSiS4, Ag2PbSiS4, Cu2PbGeS4, and Cu2SrSiS4, can be synthesized in correctly predicted phases. One of these compounds, Ag2PbSiS4, shows potentially promising optoelectronic properties for photovoltaic applications.





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Sun, JP, GC McKeown Wessler, T Wang, T Zhu, V Blum and DB Mitzi (2020). Structural Tolerance Factor Approach to Defect-Resistant I2-II-IV-X4 Semiconductor Design. Chemistry of Materials, 32(4). pp. 1636–1649. 10.1021/acs.chemmater.9b05107 Retrieved from

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Volker Blum

Rooney Family Associate Professor of Mechanical Engineering and Materials Science

Volker Blum heads the "Ab initio materials simulations" group at Duke University. Dr. Blum's research focuses on first-principles computational materials science: using the fundamental laws of quantum mechanics to predict the properties of real materials from the atomic scale on upwards.

Specific focus areas are interface and nanoscale systems with electronic and energy applications, as well as work on molecular structure and spectroscopy. He is actively working on novel semiconductor materials, including hybrid organic-inorganic perovskites and complex chalcogenide materials. Both groups of materials hold promise as absorbers for photovoltaics (i.e., solar cells), as materials for spin-based electronics and optoelectronics, and other semiconductor applications.

Dr. Blum is the coordinator of a major computer package for computational materials and molecular science based on electronic structure theory, FHI-aims. Work in his group is interdisciplinary (touching areas of physics and chemistry in addition to materials science), with opportunities for international collaboration and exchange.


David Mitzi

Simon Family Distinguished Professor

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.

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