Iridium-based selective emitters for thermophotovoltaic applications

The long-term operation of refractory-metal-based metamaterials is crucial for applications such as thermophotovoltaics. The metamaterials based on refractory metals like W, Mo, Ta, Nb, and Re fail primarily by oxidation. Here, the use of the noble metal Ir is proposed, which is stable to oxidation and has optical properties comparable to gold. The thermal endurance of Ir in a 3-layer-system, consisting of HfO2/Ir/HfO2, by performing annealing experiments up to 1240 °C in a pressure range from 2 × 10−6 mbar to 1 bar, is demonstrated. The Ir layer shows no oxidation in a vacuum and inert gas atmosphere. At temperatures above 1100 °C, the Ir layer starts to agglomerate due to the degradation of the confining HfO2 layers. An in situ X-ray diffraction experimental comparison between 1D multilayered Ir/HfO2 and W/HfO2 selective emitters annealed at 1000 °C, 2 × 10−6 mbar, over 100 h, confirms oxidation stability of Ir while W multilayers gradually disappear. The results of this work show that W-based metamaterials are not long-term stable even at 1000 °C. However, the oxidation resistance of Ir can be leveraged for refractory plasmonic metamaterials, such as selective emitters in thermophotovoltaic systems with strong suppression of long wavelength radiation.

Content

Subjects

hafnia

iridium

magnetron sputtering

selective emitters

thermophotovoltaics

thin-films

DDC Class

620: Engineering

621: Applied Physics

Funding References

Funding(s)

SFB 986: Zentralprojekt Z03 - Elektronenmikroskopie an multiskaligen Materialsystemen

SFB 986: Subproject C01- Multiscale photonic materials with adjustable absorption and thermal emission

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https://creativecommons.org/licenses/by/4.0/

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Advanced Materials - 2023 - Vaidhyanathan Krishnamurthy - Iridium‐Based Selective Emitters for Thermophotovoltaic.pdf

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