12 August 2008 Optimization of antireflection coating design for multijunction solar cells and concentrator systems
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Proceedings Volume 7099, Photonics North 2008; 709915 (2008); doi: 10.1117/12.807675
Event: Photonics North 2008, 2008, Montréal, Canada
Abstract
Photovoltaic solar cells are a route towards local, environmentally benign, sustainable and affordable energy solutions. Antireflection coatings are necessary to input a high percentage of available light for photovoltaic conversion, and therefore have been widely exploited for silicon solar cells. Multi-junction III-V semiconductor solar cells have achieved the highest efficiencies of any photovoltaic technology, yielding up to 40% in the laboratory and 37% in commercial devices under varying levels of concentrated light. These devices benefit from a wide absorption spectrum (300- 1800 nm), but this also introduces significant challenges for antireflection coating design. Each sub-cell junction is electrically connected in series, limiting the overall device photocurrent by the lowest current-producing junction. Therefore, antireflection coating optimization must maximize the current from the limiting sub-cells at the expense of the others. Solar concentration, necessary for economical terrestrial deployment of multi-junction solar cells, introduces an angular-dependent irradiance spectrum. Antireflection coatings are optimized for both direct normal incidence in air and angular incidence in an Opel Mk-I concentrator, resulting in as little as 1-2% loss in photocurrent as compared to an ideal zero-reflectance solar cell, showing a similar performance to antireflection coatings on silicon solar cells. A transparent conductive oxide layer has also been considered to replace the metallic-grid front electrode and for inclusion as part of a multi-layer antireflection coating. Optimization of the solar cell, antireflection coating, and concentrator system should be considered simultaneously to enable overall optimal device performance.
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Christopher E. Valdivia, Eric Desfonds, Denis Masson, Simon Fafard, Andrew Carlson, John Cook, Trevor J. Hall, Karin Hinzer, "Optimization of antireflection coating design for multijunction solar cells and concentrator systems", Proc. SPIE 7099, Photonics North 2008, 709915 (12 August 2008); doi: 10.1117/12.807675; http://dx.doi.org/10.1117/12.807675
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KEYWORDS
Solar cells

Antireflective coatings

Coating

Refractive index

Silicon

Absorption

Solar concentrators

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