Physical Electronics Dept.

***** Seminar *****

Gideon Segev

(PhD. student under the supervision of Prof. Yossi Rosenwaks and Prof. Abraham Kribus)

School of Electrical Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel

Photon Enhanced Thermionic Emission for Solar Energy Conversion

To date, the vast majority of solar energy conversion research focused on two parallel paths: photovoltaics and solar thermal energy conversion. Attempts were made to combine photovoltaic and thermal conversion such as cogeneration and thermo-photonics. However, these attempts did not yield very high efficiencies, and these concepts were not widely implemented. As a result, researchers are still looking for a conversion path that exploits both the photonic nature of sunlight and the high temperatures that can be achieved by focusing it.

Photon Enhanced Thermionic Emission (PETE) was recently proposed as a novel concept in solar energy conversion. Similar to traditional thermionic emission devices, a PETE device consists of a high-temperature cathode emitting energetic electrons and a lower temperature anode absorbing the electrons. By using a semiconductor cathode, optically generated electrons increase the cathode’s conduction band charge population allowing high electron emission at temperatures lower than the common range for thermionic emitters. In this seminar, we will discuss the efficiency limits of PETE devices. The theoretical efficiency limits of PETE converters can theoretically rise above 40% at concentration of 1000 suns, exceeding the Shockley Queisser limit for an ideal single junction PV cell. When coupled to secondary thermal cycle the limits were shown to be exceptionally high reaching close to 70% for a flux concentration 1000. Furthermore, unlike traditional thermionic converters, PETE conversion is possible even under isothermal conditions. Next, the loss mechanisms of more realistic PETE devices will be surveyed through elaborated models. Negative space charge between the two electrodes and surface recombination at the cathode contact are shown to heavily restrict the conversion efficiency. Implementation of back surface field layers in the form of homo-junction or hetero-junction cathodes can reduce surface recombination and bring the efficiency closer to the ideal limits.

Wednesday, December 31, 2014, at 16:00

Room 206, Wolfson Mechanical Engineering Building

You are invited to attend a lecture

By

Atef Shalabney

Institut de Science et d'Ingènierie Supramolèculaires, University of Strasbourg, Strasbourg, France

On the subject:

Light-matter strong coupling and potential for chemistry and biology

When matter is placed in the confined field of electromagnetic radiation, it can lead to modified and even new properties. This is of great interest from both the fundamental point of view as well as for many radiation engineering applications. For instance, the field confinement can lead to effects such as extraordinary optical transmission, enhanced absorption and emission of light, high-resolution spectroscopy and imaging. Under certain conditions, the light-matter interaction can become so strong that it enters the so-called strong coupling regime where new hybrid light-matter states are formed, offering a vast potential for chemistry and biology that has hardly been explored.

In this talk, I'll present the nature of enhanced optical phenomena using nanophotonics and plasmonic structures, emphasizing the applications of harnessing radiation fields into confined regions for bio-sensing and molecular detection. Then, a basic introduction to strong coupling of optically-active substances will be presented. Strong coupling of molecular vibrational transitions in the infra-red region will be particularly elaborated with new prospects to modify molecular and structural processes. New directions for exploiting strong light-matter interactions for bio-sensing and biomedical applications will be discussed.

Short biography:

Dr. Shalabney graduated from the Electrical Engineering Department of the Technion in 1997. He received his M.Sc. and Ph.D. degrees from the Electro-Optics Engineering Department at the Ben-Gurion University in the years 2010 and 2013 respectively. During his Ph.D., he worked within the group of Prof. Ibrahim Abdulhalim on developing plasmonic nanostructures to enhance the sensitivity of optical bio-sensors. In 2013, Dr. Shalabney joined the group of Prof. Thomas  Ebbesen at the University of Strasbourg, where his work has been focused on light-matter strong coupling with applications in biology and chemistry.

30 December 2014, at 15:00,

Room 011, Engineering Kitot Building