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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6

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Department: search.filters.department.Department of ChemistrySubject: search.filters.subject.Materials science, multidisciplinary

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    PublicationOpen Access
    Grain boundary engineering with nano-scale InSb producing high performance InxCeyCo4Sb12+z skutterudite thermoelectrics
    (Elsevier, 2017) Li, Han; Su, Xianli; Tang, Xinfeng; Zhang, Qingjie; Uher, Ctirad; Snyder, G. Jeffrey; Department of Chemistry; Aydemir, Umut; Faculty Member; Department of Chemistry; College of Sciences; 58403
    Thermoelectric semiconductors based on CoSb3 hold the best promise for recovering industrial or automotive waste heat because of their high efficiency and relatively abundant, lead-free constituent elements. However, higher efficiency is needed before thermoelectrics reach economic viability for widespread use. In this study, n-type InxCeyCo4Sb12+z skutterudites with high thermoelectric performance are produced by combining several phonon scattering mechanisms in a panoscopic synthesis. Using melt spinning followed by spark plasma sintering (MS-SPS), bulk InxCeyCo4Sb12+z alloys are formed with grain boundaries decorated with nano-phase of InSb. The skutterudite matrix has grains on a scale of 100-200 nm and the InSb nano-phase with a typical size of 5-15 nm is evenly dispersed at the grain boundaries of the skutterudite matrix. Coupled with the presence of defects on the Sb sublattice, this multi-scale nanometer structure is exceptionally effective in scattering phonons and, therefore, InxCeyCo4Sb12/InSb nano-composites have very low lattice thermal conductivity and high zT values reaching in excess of 1.5 at 800 K.
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    PublicationOpen Access
    Lead halide perovskite quantum dots for photovoltaics and photocatalysis: a review
    (American Chemical Society (ACS), 2022) Department of Chemistry; Peighambardoust, Naeimeh Sadat; Sadeghi, Ebrahim; Aydemir, Umut; Researcher; PhD Student; Faculty Member; Department of Chemistry; Koç University AKKİM Boron-Based Materials _ High-technology Chemicals Research _ Application Center (KABAM) / Koç Üniversitesi AKKİM Bor Tabanlı Malzemeler ve İleri Teknoloji Kimyasallar Uygulama ve Araştırma Merkezi (KABAM); College of Sciences; Graduate School of Sciences and Engineering; N/A; N/A; 58403
    Lead halide-based perovskite quantum dots (PQDs) have recently emerged as an important class of nanocrystal (NC) materials for optoelectronic and photoelec-trochemical applications. Thanks to their intriguing features including tunable band gap, narrow emission, high charge carrier mobility, remarkable light-absorbing factors, and long charge diffusion length, there has been a surge in research on lead halide-based PQDs and their applications. In this review, we showcase the fundamentals of PQDs and two principal applications including PQD solar cells (PQDSCs) and photocatalytic conversion. First, a thorough discussion on PQDSCs, their structure, surface treat-ment, and interface engineering along with their recent progress are presented. It is highlighted that the improvement of the efficiency of PQDSCs from below 10% to beyond 16% in a matter of a few years has turned them into promising candidates for future SC applications. Subsequently, the application of PQDs in photocatalytic reactions such as hydrogen production, CO2 reduction, and organic compounds' degradation is summarized. Not to mention that, despite the remarkable properties of PQDs in SCs and photocatalysis, the inferior stability of PV devices based thereon under operation as well as their poor tolerance under air, water, light, and heat impede their widespread application. For this, the practical efforts and possible solutions are extensively addressed. Finally, an outlook is provided, addressing further merits, and demerits of each application as well as prospective opportunities.