CAS: Multinary Semiconductor Nanocrystals: Increasing Complexity through Solution-Phase Chemistry

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Javier Vela of Iowa State University will study emerging and technologically relevant semiconductors comprised of multiple elements for which this type of chemistry remains underdeveloped. Because these semiconductors will be made from non-toxic and earth abundant elements, this research may open new classes of environmentally friendly and low-cost semiconductors of great potential for clean and renewable energy. To broaden participation and help build the next generation of highly qualified and diverse nanochemistry scientists, the Vela group will offer internships to first generation or under-represented undergraduates, contribute to the career development of postdoctoral fellows, and prepare first year graduate students to apply for research fellowships. Under this award, Professor Javier Vela and his team will utilize their expertise in the synthesis and spectroscopic study of optically active nanomaterials to: (1) study the evolution of perovskite chalcogenide nanocrystals for photovoltaics, (2) develop tin-based quaternary chalcohalide nanocrystals for optoelectronics, and (3) test ternary tetrahedral nanocrystals for carbon dioxide reduction. Compared to the high temperature synthesis of single crystal or bulk semiconductors, the synthesis of nanoscale multinary semiconductors from solution can be particularly challenging. Unlike unary or binary nanocrystals, the nucleation and growth of multinary nanocrystals from multiple precursors in a single, simultaneous step can be entropically demanding. In fact, metallic or binary seeds often precede the formation, through interfacial chemistry, of the final multinary nanophase. Further, multinary semiconductors often adopt more than one polymorph, each of which may contain mixed-occupancy sites or “coloring” patterns. This project will focus on multinary semiconductors that, in addition to being defect-tolerant, show increased stability to conditions of heat and high humidity or under continuous illumination. Colloidal synthesis from readily available precursors is expected to serve as a sustainable route into a wide range of functional multinary nanocrystals. Synergy among structural characterization, spectroscopic studies, and computation is expected to provide for a better understanding of multinary nanocrystal polymorphism and structure. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.