Energy Harvesting Through Thermoelectricity: An Atomic Scale - PowerPoint PPT Presentation

Energy Harvesting Through Thermoelectricity: An Atomic Scale Approach Carlos Untiedt LT-NanoLab, Dept Física Aplicada Universidad de Alicante, Spain

Alicante C. Untiedt 9/5/11 2

LT-Nanolab: Low temperatures and Nanosystems Laboratory C. Untiedt 9/5/11 3

Study Electronic Transport of small structures 4 05/09/11 Carlos Untiedt

Energy Harvesting Through Thermoelectricity: An Atomic Scale Approach  Thermoelectricity should be considered for energy harvesting towards Zero Power ICT  Research should be done at the nanoscale (atomic and molecular) to improve thermoelectrics 5

The Seebeck effect S depends on: ● Density of +/- chargers at Fermi energy ● Phonon drag ﾺ 6

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Figure of Merit (ZT) Figure of Merit (ZT) ZT is related to the thermodynamic efficiency, Figure of Merit (ZT) ✔ ZT about 1 → good; ✔ ZT about 3–4 → thermoelectrics compete with mechanical devices in efficiency. Now the best reported ZT values are in the 2–3 range. Much of the research in thermoelectric materials has focused on increasing S and reducing κ by manipulating the nanostructure of the materials. 11 J. Syder (2003) http://www.thermoelectrics.caltech.edu/thermoelectrics/index.html

12 Cronin B. Vining . Nature Materials 8, 83 - 85 (2009)

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New opportunities in atomic and molecular conductors Basic research through Scanning Tunneling Microscopies and related techniques ● Density of states can be “engineered” ● We can have a huge amount of Seebeck devices ● It could make possible to design on-chip peltier/seebeck devices ● Make use of small T gradients 15 Y. Dubi and M. Di Ventra. Rev. Mod. Phys. 83, 131 (2011)

Seebeck in molecules Carlos Untiedt Reddy et al. Science 315 , 1568 (2007) 16

Seebeck in MCBJ Seebeck in MCBJ 17

Special DOS coming from quantum effects as resonant states or electron correlation effects such as “Kondo” Nature 458, 1150 (2009) 18 05/09/11 Carlos Untiedt

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Spin Seebeck effect Spin Seebeck effect Carlos Untiedt New oportunities: using temperature gradients to build-up spin separation for spintronic devices to be combined with other new technologies (Topological Insulators) K.S. Uchida et al. Nature 455, 778 (2008) 20

Sumary Sumary ● Thermoelectricity constitutes an opportunity towards Zero Power ICT ● There has been a great advance in Thermoelectrics in the last decade ● Nanomaterials are good candidates for improving thermoelectric devices Issues Issues ● Seebeck coefficients and merit figures have to be properly understood and improved ● Nanostures including molecular and atomic conductors have to be further studied ● Integration of nanostructures in large devices should be implemented 21 (micro-fabrication, electrochemical methods,...)