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Proceedings Paper

Spectrum splitting and directivity control by optical metasurfaces integrated in photovoltaic devices (Conference Presentation)
Author(s): Verena Neder; Floris Uleman; Andrea Cordaro; Albert Polman

Paper Abstract

We design optical metagratings that enable the control of spectrum and directivity of light in mono- and multi-junction solar cells. First, we demonstrate 1 D Si metagratings that create directional scattering creating red-colored solar cells for rooftop application. Second, we create a spectrum splitting metasurface to optimize the light absorption performance of 4-terminal perovskite-silicon solar cells. The base units in our scattering designs are Si nanobars and nanocylinders that scatter light in a well-defined spectral band. When placed on a transparent substrate light is preferentially scattered on resonance, while off-resonant light is transmitted. By choosing an appropriate shape of the scatterers in the unit cell we suppress zero-order reflection. The metagrating directivity is controlled by the diffraction channels and is tuned by changing the array pitch. We demonstrate a colored PV module glass for rooftop application that reflects a red spectral band around 650 nm under angles between 30-75 degrees. This metasurface is composed Si nanobars arranged in differently pitched 1 D gratings that together results in a Lambertian-like scattering profile between 30-75 degrees. The reflectivity is tuned to 10% around 650 nm to achieve a clear perception of the red color, while keeping optical losses minimal. We fabricate the grating metasurface on top of a Si heterojunction solar cell and show experimentally that the short-circuit current of the cell is only reduced by 7%. Next, we design a semi-transparent spectrum splitting metasurface to improve the performance of perovskite-silicon 4-terminal tandem devices. A 2D hexagonal grid of amorphous silicon cylinders is placed at the Si/perovskite interface and resonantly scatters upward the 600-800 nm spectral band that is otherwise incompletely absorbed in the perovskite. The spectrum splitting layer redirects light into the perovskite under a steep angle (50-90 degrees), resulting in total internal reflection inside the perovskite and thus enhanced light trapping. An absolute improvement of over 1% of the overall tandem efficiency may be achieved.

Paper Details

Date Published: 1 April 2020
Proc. SPIE 11366, Photonics for Solar Energy Systems VIII, 113660O (1 April 2020); doi: 10.1117/12.2555743
Show Author Affiliations
Verena Neder, AMOLF (Netherlands)
Floris Uleman, AMOLF (Netherlands)
Andrea Cordaro, AMOLF (Netherlands)
Albert Polman, AMOLF (Netherlands)

Published in SPIE Proceedings Vol. 11366:
Photonics for Solar Energy Systems VIII
Alexander N. Sprafke; Jan Christoph Goldschmidt; Gregory Pandraud, Editor(s)

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