Title:
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Mid-infrared emissivity of crystalline silicon solar cells
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Author:
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Riverola Lacasta, Alberto; Mellor, A.; Alonso Alvarez, D.; Ferre Llin, L.; Guarracino, I.; Markides, C. N.; Paul, D. J.; Chemisana Villegas, Daniel; Ekins-Daukes, N.
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Notes:
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The thermal emissivity of crystalline silicon photovoltaic (PV) solar cells plays a role in determining the operating temperature of a solar cell. To elucidate the physical origin of thermal emissivity, we have made an experimental measurement of the full radiative spectrum of the crystalline silicon (c-Si) solar cell, which includes both absorption in the ultraviolet to near-infrared range and emission in the mid-infrared. Using optical modelling, we have identified the origin of radiative emissivity in both encapsulated and unencapsulated solar cells. We find that both encapsulated and unencapsulated c-Si solar cells are good radiative emitters but achieve this through different effects. The emissivity of an unencapsulated c-Si solar cell is determined to be 75% in the MIR range, and is dominated by free-carrier emission in the highly doped emitter and back surface field layers; both effects are greatly augmented through the enhanced optical outcoupling arising from the front surface texture. An encapsulated glass-covered cell has an average emissivity around 90% on the MIR, and dips to 70% at 10 µm and is dominated by the emissivity of the cover glass. These findings serve to illustrate the opportunity for optimising the emissivity of c-Si based collectors, either in conventional c-Si PV modules where high emissivity and low-temperature operation is desirable, or in hybrid PV-thermal collectors where low emissivity enables a higher thermal output to be achieved.
This research was supported by the 'Ministerio de Economía y
Competitividad' of Spain (grants ENE2013-48325-R, BES-2014-069596
and EEBB-I-16-11459) and the by the UK Engineering and Physical
Science Research Council (EPSRC) [grant number EP/M025012/1]. A.
Mellor was supported by the European Commission through Marie
Sklodowska Curie International Fellowship, Grant No. DLV-657359.
Re
fl
ection and Transmission measurements were performed by Dr.
Volker Kübler in the Micro-structured Surfaces Group of Fraunhofer-
ISE, Freiburg, Germany. |
Subject(s):
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-Emissivity -Mid-infrared -Normal cell operating temperature -Hybrid photovoltaic-thermal |
Rights:
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cc-by-nc-nd (c) Elsevier, 2017
http://creativecommons.org/licenses/by-nc-nd/4.0/
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Document type:
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Article Article - Accepted version |
Published by:
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Elsevier
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