Session Y36: Physics For Everyone & Student Award Symposium

Sustainable manufacturing supply chains for vehicle electrification

The United States and many other countries have placed electric vehicles at the center of strategies to decarbonize the light duty fleet. Based on life cycle assessments, per mile driven, electric vehicles emit a lower amount of greenhouse gases than conventional vehicles. This result accounts for increased emissions during vehicle manufacturing, which are largely attributable to manufacturing lithium-ion batteries. However, life cycle assessments that focus on greenhouse gas emissions may miss other environmental effects of manufacturing electric vehicle batteries that should be addressed to drive society towards a just transition to an electrified vehicle fleet. These include water and air pollution from minerals mining activities. Notably, most electric vehicle battery manufacturing along with acquisition of the minerals the batteries contain occur overseas. With the passage of the Inflation Reduction Act, the supply chain is shifting as investments are made to ramp up domestic minerals production and battery manufacturing. These shifts are occurring alongside other developments and changes in the international supply chain. Each of these shifts bring environmental and social effects. Life cycle assessment is a valuable tool to evaluate the overall sustainability of lithium-ion battery manufacturing. I will describe how this holistic analysis framework along with material flow analysis can help us design and pursue a battery supply chain that is tailored to limit negative environmental and social effects of lithium-ion battery manufacturing.   

Reducing cement and concrete environmental impact: a physicist's perspective

Cement is the main binding agent in concrete, literally gluing together rocks and sand into the most-used synthetic material on Earth. However, cement production is responsible for significant amounts of man-made greenhouse gases—in fact if the cement industry were a country, it would be the third largest emitter in the world. It has become clear that even a slight reduction of cement carbon footprint will dramatically reduce the global anthropogenic CO2 emissions of the whole construction sector, and that meeting emission-reduction targets for new constructions calls for deeper scientific understanding of cement properties and performance. I will analyze recent insights into the physics of this complex material and how they open a new path to scientifically grounded strategies of material design for greener cements. I will also discuss how physicists and policy experts can work together to devise available strategies for reducing cement and concrete environmental impact, and the role that new technologies, such as additive manufacturing, can play.   

Greene Dissertation Award Winner: Characterising nanostructure and understanding its influence on phase stability in halide perovskites

Halide perovskites possess exceptional characteristics for the next generation of low-cost optoelectronic applications. Photovoltaic (PV) devices fabricated from perovskite absorbers already exhibit certified power conversion efficiencies exceeding 25.5% in single-junction devices and 32% in tandem configurations. However a number of challenges remain before perovskites can be widely commercialized. For instance, in spite of their high performance, perovskites still exhibit a sizeable density of deep sub-gap non-radiative trap states1,2 that lead to local variations in photoluminescence and ultimately limit device performance. Understanding the origin and nature of these traps is critical to further reduce losses and yield devices operating at close to their theoretical limits. In this talk, we use correlated nanoscale characterisation methodologies to explore the nanoscopic landscape of beam-sensitive halide perovskite materials. Utilising Scanning Electron Diffraction, in particular, we show that deep trap states in perovskite materials are correlated with the presence of nm scale phase impurities1 that include hexagonal wide bandgap perovskite polytypes and PbI2. We then show that these same phase impurities that are responsible for performance losses, seed material degradation in the perovskite absorber layer under operational conditions6. Finally, we show that state-of-the-art alloyed formamadinium lead iodide-like perovskites are non-cubic on average, exhibiting slight octahedral tilting at room temperature. This octahedral tilting, induced by cationic additives, frustrates the transition between the photoactive and hexagonal perovskite phases7 thus providing an intrinsic barrier to phase impurity formation. However, local regions of a perovskite film without octahedral tilting can rapidly transition to the nm sized hexagonal phase impurities that cause deep traps and seed material degradation.   

Greene Dissertation Award Winner: Negative Capacitance Electronics: Manipulating Ferroelectricity in Atomically Thin Simple Materials

The explosion in energy consumption from microelectronics is projected to exceed 20% of worldwide electricity production by 2030 and is continuing to exponentially rise, which calls for fundamental breakthroughs in information processing and on-chip energy technologies. In this talk, I will introduce electronic metamaterials as a new atomic scale platform towards this goal of energy-efficient and energy-autonomous electronics, in which negative capacitance phenomena lead to unprecedented charge responses beyond what is possible in traditional materials. All discoveries will be demonstrated in the model system of HfO₂-ZrO₂ thin films on Si, the conventional dielectrics in today’s microelectronics, to establish atomic-scale confinement of simple 3D materials – down to its unit cell thickness – as a powerful strategy to unlock previously hidden electronic phenomena. I will primarily present the microscopic origins underlying negative capacitance behavior in ultrathin HfO₂-ZrO₂ films, namely frustrated ferroelectric-antiferroelectric order and negative piezoelectricity, and how manipulating symmetry in atomically thin heterostructures can stabilize such ground states. In closing, I will briefly establish negative capacitance effects in ultrathin HfO₂-ZrO₂ films as a new paradigm for (i) ultra-low power computing beyond conventional high permittivity dielectric transistors and (ii) ultra-fast energy storage beyond conventional electrochemical supercapacitors.