| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018) | |
| Energy Harvesting & Storage | Tuesday Sessions |
| Session EH-TuP |
| Session: | Energy Harvesting and Storage Poster Session |
| Presenter: | Gregory Abadias, Institut Pprime, CNRS-Université de Poitiers, France |
| Authors: | G. Abadias, Institut Pprime, CNRS-Université de Poitiers, France Y. Metayrek, Institut Pprime, CNRS-Université de Poitiers, France A. Michel, Institut Pprime, CNRS-Université de Poitiers, France J. Drevillon, Institut Pprime, CNRS-Université de Poitiers, France |
| Correspondent: | Click to Email |
One of the key points for designing high-efficiency thermophotovoltaic (TPV) systems is to match the spectral emission of the radiator with the spectral range where photons are converted into electron-hole pairs inside the photovoltaic device. Recent studies have shown the potential offered by photonic crystals made of metal/dielectric stack of layers acting as Fabry-Pérot cavity, ensuring spectral selectivity to the emitter. Another material requirement is thermal stability in order to keep the same spectral emission at the operating temperature of the radiator. The Mo/HfO2 system is a promising candidate material in this respect, as recently reported by Blandre et al. [1].
In this work we investigate the synthesis by magnetron sputtering of W/HfO2 four-layer films for TPV applications. The individual layer thicknesses were optimized based on fluctuational electrodynamics calculations of thermal emissivity of one-dimensional layered media. Prior to the fabrication of the multilayer stack, the structure and optical properties of the transparent HfO2 layer were investigating as a function of process parameters: substrate temperature Ts and O2 flow rate.
Films were characterized by X-ray reflectivity, X-ray diffraction and wavelength dispersive spectroscopy. The optical indices (n and k) were measured experimentally from variable angle spectroscopic ellipsometry in the visible and mid-infrared (MIR) range (up to 35 μm). Results show that dense, crystalline HfO2 layers with monoclinic structure can be formed by reactive magnetron sputtering at room temperature with optical index n close to 2.1 at 550 nm; however, crystallinity was improved by increasing Ts up to 500°C, with little variation on n and k. In the MIR, the optical properties of HfO2 were consistent with the data reported by Bright et al. [2].The optical reflectance of the W/HfO2 stack was measured using spectrophotometer and a good agreement with theoretical predictions was found, attesting of the potential of this system for TPV emitters.