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At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-07-01 |
| Journal | Electronics Letters |
| Authors | Anonymous |
Abstract
Section titled âAbstractâDr Marco Girolami from the Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia in Italy, talks about the work behind the Letter, âHigh-temperature electric contacts for AlGaInP/GaInP photon-enhanced thermionic emission cathodesâ, page 945. Dr Marco Girolami Since I was a PhD student, my primary research activity has always been the design, fabrication and characterisation of diamond detectors for ionising radiation (X-rays, gamma-rays) and nuclear particle monitoring (alpha and beta particles, neutrons), together with the development and testing of front-end and read-out electronics for data elaboration. In 2013, in the framework of the European FP7-Energy Project ProME3ThE2US2 (âProduction Method of Electrical Energy by Enhanced Thermal Electron Emission by the Use of Superior Semiconductorsâ), I started working on the development of solar energy conversion modules based on photon-enhanced thermionic emission (PETE). This is a promising technique for concentrating solar systems which exploits both solar photon absorption and high-temperature-triggered thermionic emission, and can potentially overcome the limitations of conventional photovoltaics. At the moment, Iâm interested in the development of efficient cost-effective technologies for a more sustainable energy economy. I think that energy issues are indeed of primary importance in the world of applied research, which should open new paths for the production of clean energy from renewable sources, or further investigate the existing ones to optimize their performance. Our letter makes a little but significant step forward in the development of efficient solar energy conversion modules based on PETE from III-V semiconductors. The Fraunhofer Institute for Solar Energy System, with which we collaborate, recently developed a PETE cathode, based on an AlGaInP/GaInP heterostructure, potentially able to work stably at temperatures higher than 400 °C. In this Letter, we report on the results of a preliminary selection of possible contact electrode materials able to guarantee the device high performance even at high operating temperatures. In particular, we studied three metals (gold, silver, and titanium) and a carbide (tungsten carbide): results reported here show that titanium is the best choice. In concentrating solar power systems, for a reliable electrical power production, it is necessary to ensure that the metal contacts connecting the conversion module to the external circuit are stable at the high temperatures that can be reached, without affecting the conversion efficiency of the device. By adopting titanium contacts, which showed the best trade-off between low contact resistivity and high mechanical robustness, AlGaInP/GaInP-based PETE conversion modules are expected to work at a temperature of at least 350 °C without degrading their performance. Contact electrodes able to maintain their electrical and mechanical properties at high temperatures (up to 350-400 °C) may find application not only in semiconductor-based conversion modules for concentrating solar power systems, as reported in this Letter, but also in other fields in which high operating temperatures are concerned (e.g. electronic devices for harsh environments, oil and gas industries, avionics, automotive). My group is now involved in a new European project (H2020 Future Emerging Technology), named AMADEUS, on the development of ultra-high temperature energy storage systems, able to perform a direct conversion of heat into electricity. Such systems are based on thermionic-photovoltaic (TIPV) solid-state devices, able to transform into electricity both the electron and photon fluxes emitted by an incandescent surface. Potential applications are the direct storage of solar energy in thermal solar power plants, or the integration of both electric power storage and cogeneration in the housing sector and urban areas. I approached the world of conversion modules for solar concentrating systems only four years ago, so itâs too early for me to notice changes. As for the future perspectives, I think that significant efforts will be spent in the optimisation of the devices already developed in the lab, in order to increase their technology readiness level and, hopefully, present them on the market as high-efficiency alternatives to conventional solar energy converters. The main challenge is to turn the outstanding conversion efficiency values of PETE systems (> 50%) from theoretical to practically achievable. At the moment, efficiency of prototypes hardly exceeds 8-10%, but the technological reasons that limit their performance have already been identified, and research activities of several groups worldwide are ongoing to overcome these limitations.