Engineered nanostructured thin films for thermionic-photovoltaic energy conversion at ultra-high temperatures
| Main Authors: | Trucchi, Daniele M., Bellucci, A., Generosi, A., Girolami, M, Mastellone, M., Orlando, S., Paci, B, Valentini, V., Polini, R., Mezzi, A., Kaciulis, S., Datas, A., Antolin, E., Linares, P.G., Villa,, J., Martì, A. |
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| Format: | info Proceeding Journal |
| Terbitan: |
, 2018
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/1306232 |
Daftar Isi:
- The H2020FET-OPEN project AMADEUS proposes the proof-of-concept of a novel solar thermal energy storage system based on phase change materials, such as pure silicon and boron with a high melting point (>1400 °C) and a high latent heat capacity (10 times higher than the molten salts), combined with a solid-state energy conversion mechanism based on a hybrid thermionic-photovoltaic (TIPV) device. The TIPV cell, operating at very high temperatures (up to 2000 °C) produces and exploits high electronic and photonic fluxes to convert heat directly and efficiently into electric power at very high power rates. Specifically, our main aim is the development of low work-function thermionic electrodes able to manage a large current density at the operating temperatures. The thermionic cathode is under development with the deposition of thin films of nanostructured borides (lanthanum, cerium) obtained by nanosecond and femtosecond pulsed laser deposition and/or electron-beam evaporation on refractory substrates. Single-crystal borides already demonstrated to be efficient thermionic emitters due to a low work function (typically < 3 eV) and a high melting point (>2200 °C). The challenge here is to extend these properties to low-cost large-area nano/micro-structured boride thin layers. On the other hand, the anode of the TIPV converter is a thin layer deposited on a PV cell. The layer, with a work-function even lower than the cathode one to collect the emitted electrons, must also be transparent to the blackbody radiation coming from the hot cathodic component so to allow the PV cell to exploit this photon flux. Ultra-thin layers of alkali metal compounds (barium and caesium) are under development by electron-beam evaporation and magnetron sputtering as anodic coatings. Grazing incidence x-ray diffraction, scanning-electron and atomic-force microscopies, Raman and x-ray spectroscopies were used to investigate the chemical-physical properties of all the deposited thin films, allowing us to optimize their functional properties. Ultraviolet photo-spectroscopy and thermionic emission measurements were performed to evaluate the work-functions and the operating temperature ranges of the emitting/collecting layers.