Flexible thin film optical solar reflectors with Ta2O5-based multimaterial coatings for space radiative cooling
Flexible thin film optical solar reflectors with Ta2O5-based multimaterial coatings for space radiative cooling
Optical Solar Reflectors (OSRs) combine low solar radiation absorption (α) and high broadband infrared emissivity (ϵ) and are applied to the external surface of spacecraft for its thermal management. Bulk glass OSR tiles are the incumbent, but ultra-lightweight and thin-film flexible OSR coatings are raising considerable interest for both space and terrestrial radiative cooling applications. In this work, a genetic algorithm combined with a transfer matrix method is used for the design and optimization of multimaterial thin-film OSRs for broadband radiative cooling. The algorithm simultaneously optimizes the spectral performance of the OSR at two parts of the wavelength spectrum, solar (0.3-2.5 μm) and thermal infrared (2.5-30 μm). The designed optimized OSR structure consists of 18 alternating layers of three materials, SiN, SiO
2, and Ta
2O
5, on top of an Al mirror backreflector, with a total thickness of only 2.088 μm. The optimized multilayer stack contributes distributed Bragg reflections that reduce the residual solar absorption below that of an uncoated Al mirror. The optimized OSR is demonstrated experimentally on a 150 mm (6 in.) Si wafer and on a flexible polyimide substrate using a production level reactive sputtering tool. The fabricated thin film OSR shows good thermal-optical property with α = 0.11 and ϵ = 0.75 and achieves a net cooling power of 150.1 W/m
2 under conditions of one sun total solar irradiance in space. The ultrathin coating fabricated using hard inorganic materials facilitates its integration onto flexible foils and enables large-scale manufacture of low-cost OSRs for broadband radiative cooling applications.
Xiao, Wei
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Dai, Peng
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Singh, H. Johnson
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Ajia, Idris A.
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Yan, Xingzhao
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Wiecha, Peter R.
fb335482-9577-41af-a0ef-3988b7654c9b
Huang, Ruomeng
55c6fba5-0275-4471-af5c-fb0dd2daaa64
De Groot, C.H. (kees)
92cd2e02-fcc4-43da-8816-c86f966be90c
Muskens, Otto L.
2284101a-f9ef-4d79-8951-a6cda5bfc7f9
Sun, Kai
b7c648a3-7be8-4613-9d4d-1bf937fb487b
4 September 2023
Xiao, Wei
20758ef4-698c-46e5-bb9b-a97db7340379
Dai, Peng
1150a00a-e54b-438b-bf51-4e8521c07f66
Singh, H. Johnson
709a93d7-e379-4c3f-86e2-3dc39b11eeb4
Ajia, Idris A.
6c3d6040-2701-43c9-a7d1-a55ba45ab510
Yan, Xingzhao
320b9089-1fb3-485a-8c1f-45fb1f86efa0
Wiecha, Peter R.
fb335482-9577-41af-a0ef-3988b7654c9b
Huang, Ruomeng
55c6fba5-0275-4471-af5c-fb0dd2daaa64
De Groot, C.H. (kees)
92cd2e02-fcc4-43da-8816-c86f966be90c
Muskens, Otto L.
2284101a-f9ef-4d79-8951-a6cda5bfc7f9
Sun, Kai
b7c648a3-7be8-4613-9d4d-1bf937fb487b
Xiao, Wei, Dai, Peng, Singh, H. Johnson, Ajia, Idris A., Yan, Xingzhao, Wiecha, Peter R., Huang, Ruomeng, De Groot, C.H. (kees), Muskens, Otto L. and Sun, Kai
(2023)
Flexible thin film optical solar reflectors with Ta2O5-based multimaterial coatings for space radiative cooling.
APL Photonics, 8 (9), [090802].
(doi:10.1063/5.0156526).
Abstract
Optical Solar Reflectors (OSRs) combine low solar radiation absorption (α) and high broadband infrared emissivity (ϵ) and are applied to the external surface of spacecraft for its thermal management. Bulk glass OSR tiles are the incumbent, but ultra-lightweight and thin-film flexible OSR coatings are raising considerable interest for both space and terrestrial radiative cooling applications. In this work, a genetic algorithm combined with a transfer matrix method is used for the design and optimization of multimaterial thin-film OSRs for broadband radiative cooling. The algorithm simultaneously optimizes the spectral performance of the OSR at two parts of the wavelength spectrum, solar (0.3-2.5 μm) and thermal infrared (2.5-30 μm). The designed optimized OSR structure consists of 18 alternating layers of three materials, SiN, SiO
2, and Ta
2O
5, on top of an Al mirror backreflector, with a total thickness of only 2.088 μm. The optimized multilayer stack contributes distributed Bragg reflections that reduce the residual solar absorption below that of an uncoated Al mirror. The optimized OSR is demonstrated experimentally on a 150 mm (6 in.) Si wafer and on a flexible polyimide substrate using a production level reactive sputtering tool. The fabricated thin film OSR shows good thermal-optical property with α = 0.11 and ϵ = 0.75 and achieves a net cooling power of 150.1 W/m
2 under conditions of one sun total solar irradiance in space. The ultrathin coating fabricated using hard inorganic materials facilitates its integration onto flexible foils and enables large-scale manufacture of low-cost OSRs for broadband radiative cooling applications.
Text
090802_1_5.0156526
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e-pub ahead of print date: 4 September 2023
Published date: 4 September 2023
Additional Information:
Funding Information:
O.L.M. and K.S. acknowledge the support from EPSRC through an Impact Acceleration Account project. The authors acknowledge the support from DuPont for freely providing DuPont Kapton PFC 300 as polyimide substrates. ®
Publisher Copyright:
© 2023 Author(s).
Identifiers
Local EPrints ID: 482896
URI: http://eprints.soton.ac.uk/id/eprint/482896
ISSN: 2378-0967
PURE UUID: 0d708c86-582b-40bc-8137-0870f75ba450
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Date deposited: 16 Oct 2023 16:56
Last modified: 18 Mar 2024 03:55
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Contributors
Author:
Peng Dai
Author:
H. Johnson Singh
Author:
Xingzhao Yan
Author:
Peter R. Wiecha
Author:
Ruomeng Huang
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