Bulletin of the American Physical Society
76th Annual Meeting of the Southeastern Section of APS
Volume 54, Number 16
Wednesday–Saturday, November 11–14, 2009; Atlanta, Georgia
Session GB: Energy, Conversion, Storage and Future Trends |
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Chair: Ahmet Erbil, Georgia Institute of Technology Room: Frankfurt |
Friday, November 13, 2009 8:30AM - 9:00AM |
GB.00001: Electronic properties of Single Impurities and Defects in PV Materials Invited Speaker: Approaching the theoretical limits of solar cell efficiencies necessitates advances in the understanding of impurity and defects physics in photovoltaic material. Using optical spectroscopy with diffraction limited spatial resolution, it is possible to study the luminescence from single impurity centers in a semiconductor. By selectively studying individual impurity centers formed by two neighboring nitrogen atoms in GaAs1-xNx, I will show that one can identify their particular impurity configuration, map their spatial distribution, and demonstrate the presence of a diversity of local impurity-host environments. Circumventing the limitation imposed by ensemble averaging and the ability to discriminate individual electronic responses from discrete impurities provides an unprecedented perspective on the nanoscience of impurities in photovoltaic material. The ternary semiconductor alloy GaInP2 plays a very prominent role in High-Efficiency Multijunction Solar Cells as well as in Solid-State Lighting. The size-mismatch induced strain between the binary components of the alloy leads to spontaneous ordering, that results in dramatic changes to the electronic and optical properties. In addition to bandgap lowering, spontaneous ordering is accompanied by stacking fault defects which are poorly understood. I will discuss a novel photoluminescence (PL) snapshot technique that has been recently developed to probe the electronic properties originating from the microstructure of these defects. [Preview Abstract] |
Friday, November 13, 2009 9:00AM - 9:30AM |
GB.00002: Solar Photovoltaics Technology: The Revolution Begins . . . Invited Speaker: The prospects of current and coming solar-photovoltaic (PV) technologies are envisioned, arguing this solar-electricity source is at a tipping point in the complex worldwide energy outlook. The emphasis of this presentation is on R\&D advances (cell, materials, and module options), with indications of the limitations and strengths of crystalline (Si and GaAs) and thin-film (a-Si:H, Si, Cu(In,Ga)(Se,S)$_{2}$, CdTe). The contributions and technological pathways for now and near-term technologies (silicon, III-Vs, and thin films) and status and forecasts for next- generation PV (organics, nanotechnologies, non-conventional junction approaches) are evaluated. Recent advances in concentrators with efficiencies headed toward 50\%, new directions for thin films (20\% and beyond), and materials/device technology issues are discussed in terms of technology progress. Insights into technical and other investments needed to tip photovoltaics to its next level of contribution as a significant clean-energy partner in the world energy portfolio. The need for R\&D accelerating the now and imminent (evolutionary) technologies balanced with work in mid-term (disruptive) approaches is highlighted. Moreover, technology progress and ownership for next generation solar PV mandates a balanced investment in research on longer-term (the revolution needs revolutionary approaches to sustain itself) technologies (quantum dots, multi-multijunctions, intermediate-band concepts, nanotubes, bio-inspired, thermophotonics, solar hydrogen. . . ) having high-risk, but extremely high performance and cost returns for our next generations of energy consumers. Issues relating to manufacturing are explored-especially with the requirements for the next-generation technologies. This presentation provides insights into how this technology has developed-and where the R\&D investments should be made and we can expect to be by this mid-21st century. [Preview Abstract] |
Friday, November 13, 2009 9:30AM - 10:00AM |
GB.00003: Bio-Inspired Solar Energy Conversion Invited Speaker: The areas of solar-powered catalysts for energy rich fuels formation and bio-inspired molecular assemblies for integrating photon-to-fuels pathways have been identified by the Office of Basic Energy Sciences of the U. S. Department of Energy as challenges for the next generation of sustainable, high-efficiency solar energy conversion systems [1]. The light-harvesting, energy-transducing and carbon compound-synthesizing (carbon dioxide-fixing) reactions that are encompassed by natural photosynthesis offer molecular paradigms for efficient free energy capture and storage. We seek to emulate these features in cell-free, protein-based systems. Our goal is to transform the robust (alpha,beta)8-barrel fold of an enzyme that naturally catalyzes radical reactions into a catalytic module for the reduction of carbon dioxide to formate, by using the cobalt-containing cobalamins and other organocobalt centers. The activation of the catalytic center will be driven by photo-reduction, by using soluble and attached organic or semiconductor architectures. Progress on the biochemical, chemical, physical, and molecular biological (including rational design of high binding affinity and reactivity towards carbon dioxide) approaches to the development of the photocatalytic system will be presented.\\[4pt] [1] Lewis, N.; Crabtree, G. In: Basic Research Needs for Solar Energy Utilization, Basic Energy Sciences Workshop on Solar Energy Utilization, Energy, U.S. Department of Energy, Office of Science: 2005. [Preview Abstract] |
Friday, November 13, 2009 10:00AM - 10:30AM |
GB.00004: Novel materials for advanced supercapacitors and Li-ion batteries Invited Speaker: High power energy storage devices, such as supercapacitors and Li-ion batteries, are critical for the development of zero-emission electrical vehicles, large scale smart grid, and energy efficient cargo ships and locomotives. The energy storage characteristics of supercapacitors and Li-ion batteries are mostly determined by the specific capacities of their electrodes, while their power characteristics are influenced by the maximum rate of the ion transport. The talk will focus on the development of nanocomposite electrodes capable to improve both the energy and power storage characteristics of the state of the art devices. Advanced ultra-high surface area carbons, carbon-polymer, and carbon-metal oxide nanocomposites have been demonstrated to greatly exceed the specific capacitance of traditional electrodes for supercapacitors. In addition, selected materials showed the unprecedented ultra-fast charging and discharging characteristics. Intelligently designed Si-C composites showed up to 5 times higher specific capacity than graphite, the conventional anode material in Li-ion batteries. Achieving stable performance of Si anodes is commonly a challenge. Recent experiments suggest that individual Si nanoparticles and thin films below a critical size do not fracture and exhibit high reversible capacity for Li. The often observed rapid degradation of Si-based anodes is related not to the intrinsic property of Si but to the loss of electrical contact within the anodes caused by the large volume changes that takes place during Li insertion and extraction. Successful synthesis of high capacity nanocomposite Si-C particles that do not exhibit volume changes during Li insertion and extraction allowed us to achieve stable performance. In order to overcome the limitations of traditional composites precise control over the materials' structure and porosity at the nanoscale was required. [Preview Abstract] |
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