DATE: Thursday, July 30 - Thursday, August 06, 2020
TIME: 12:00 AM - 12:00 AM
DATE: Monday, August 10, 2020
TIME: 02:00 PM - 04:00 PM
Zoom Link: https://kaust.zoom.us/j/96005124178 ABSTRACT: Semiconducting materials have emerged as the cornerstone of modern electronics owing to their extensive device applications. There is a continuous quest to find cost-effective and low-temperature compatible materials for future electronics. The recent reemergence of solution processable halide perovskites have taken the optoelectronics research to new paradigms. Apart from photovoltaics, the versatile characteristics of halide perovskites have resulted in a multitude of applications. This dissertation mainly focuses on various properties and emerging applications particularly, photodetection and thermoelectrics of both hybrid and all-inorganic halide perovskites. It is important to understand the underlying properties of perovskites to further develop this class of materials. One of the major hurdles restricting the practical devices of perovskites is their sensitivity to moisture. A systematic investigation on the effect of humidity on hybrid perovskites revealed different degree of moisture uptake behaviour for micropatterns, films, and single crystals. Degradation pathways and processing limitations of hybrid perovskites are discussed which will aid in designing strategies to overcome these impediments for future large scale device integration. There is a recent surge of reports on doping hybrid perovskites to control its optoelectronic properties but in-depth understanding of these dopants and their ramifications remain unexplored. The effect of doping on the optoelectronic properties of hybrid perovskites is studied and a model is proposed for the observed behavior. Leveraging on the rapid growth of microcrystalline perovskite films, for the first time tunable bifacial perovskite photodetectors were fabricated, operating in both broadband and narrowband regimes. Furthermore, self-biased single crystalline photodetectors based on all-inorganic perovskite were developed with high on-off ratio and low dark current. Halide perovskites are emerging as a new class of materials for thermoelectric applications owing to their ultralow thermal conductivity and decent Seebeck coefficient. Here, halide perovskites are evaluated in terms of composition, stability, and performance tunability to understand their thermoelectric efficacy. Finally, as an alternative to Pb and Sn-based perovskites, a new hybrid was discovered with ultralow thermal conductivity and a general synthetic route to design such hybrids is proposed.
DATE: Wednesday, August 12, 2020
TIME: 03:00 PM - 04:00 PM
LOCATION:KAUST, VIA ZOOM, CLICK OR COPY THE LINK BELOW
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Abstract: Halide perovskites have recently emerged as the state-of-the-art semiconductors with the unique combination of outstanding optoelectronic properties and facile solution synthesis. Within only a decade of research, their polycrystalline thin films have already achieved a remarkable success in photovoltaics, competing now with the high-quality inorganic semiconductors. Yet, grain boundaries in these polycrystalline thin films have been found to act as non-radiative recombination centers and facilitate the material’s degradation, adversely affecting the device performance. On the other hand, single crystals of halide perovskites – which are free of grain boundaries – exhibit even superior charge transport characteristics and environmental stability over their polycrystalline alternatives.
In this regard, my dissertation focuses on the design, growth and characterization of halide perovskite single crystals. Particularly, we investigate their fundamental optical and charge transport properties, as well as develop crystal engineering approaches toward their applications in optoelectronics.
DATE: Monday, September 28, 2020
TIME: 12:00 PM - 01:00 PM
Standard test methods to determine delamination resistance impose significant constraints on the specimen geometry and stacking sequence, thus they do not enable direct evaluation of the fracture toughness in many configurations of real-life practical interest (such as non-flat geometries, non-midplane delamination, [a/b] interfaces). In this talk, some alternative testing configurations are introduced and explored, enabling us to tackle these difficulties and achieve information on more general (co-cured or bonded) interfaces. The advantages and drawbacks of the different testing configurations are discussed, as well as the mechanical significance of the measured interface characteristics with respect to the classical testing methods.
Federica Daghia is Adjunct Professor (Maître de Conférences HDR) at the École Normale Supérieure Paris-Saclay. She is secretary of the French Society for Composite Materials, as well as member of the French National Committee for Scientific Research, Division 9 (Mechanics of Solids, Materials and Structures, Biomechanics, Acoustics). Her research interest revolve around the modeling, experimental characterization and simulation of the behaviour until failure of architectured materials, including polymer matrix composites.
To be updated later
DATE: Wednesday, February 17, 2021
TIME: 04:15 PM - 05:15 PM