Preparation and Characterization of Solar Thermal Absorbers by Nanoimprint Lithography and Sputtering
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.285
Preparation and Characterization of Solar Thermal Absorbers by Nanoimprint Lithography and Sputtering Tina Mitteramskogler1, Michael J. Haslinger1, Ambiörn Wennberg2, Iván FernandezMartínez2, Michael Muehlberger1, Matthias Krause3 and Elena Guillén1 1
PROFACTOR GmbH, Im Stadtgut A2, 4407 Steyr-Gleink, Austria Nano4Energy SL, José Gutiérrez Abascal 2, 28006 Madrid, Spain Helmholtz-Zentrum Dresden-Rossendorf e.V., Bautzner Landstraße 400, 01328 Dresden, Germany
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ABSTRACT
Selective solar absorbers comprised of plasmonic materials offer great flexibility in design along with a highly promising optical performance. However, the nanopattern generation, typically done with electron beam writing, is a very time-intensive process. In this work, we present a fast, scalable, and flexible method for the fabrication of plasmonic materials by the combination of a deposition mask prepared by nanoimprint lithography and thin film deposition by magnetron sputtering. The fabrication process was first performed on silicon wafer substrates using AFM and SEM measurements to calibrate the deposition time, determine maximal deposition height, and characterize samples. Afterwards, the process was transferred to polished Inconel NiCr-alloy substrates used in high temperature solar absorbers. To investigate the adhesion properties of the nanostructure on the substrate, two different deposition methods were investigated: DC magnetron sputtering and High Power Impulse Magnetron Sputtering (HiPIMS).
INTRODUCTION Concentrated solar power systems generate electrical energy by harvesting the sunlight shining upon a large area and focussing it onto an absorber tube. There, the solar radiation is converted to heat and subsequently to electrical energy. An ideal absorber, capable of harvesting solar power efficiently, is characterised by a high absorption and ability to capture the incoming energy while supressing thermal re-emission. Since absorption and emission spectra are closely linked, a balance needs to be found in order to mimic an ideal blackbody absorber in the solar spectral range (0.3 – 2.5μm) while
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having low thermal emittance in the infrared region (2.5 – 30 μm). An ideal solar absorber must be highly wavelength selective and characterised by a sharp temperaturedependent cut-off wavelength. [1] There are various approaches for the design of selective solar absorbers, including intrinsic absorbers, cermets, multilayer structures, photonic crystals and plasmonic materials [1,2]. What sets the plasmonic absorbers apart is their optical selectivity, as well as the tuneability of their optical properties [1–5]. Regarding the materials, various designs have been proposed based on tungsten [6,7], silver [8], gold [2,9
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