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Photonic structures for III-V//Si multijunction solar cells with efficiency >33%
Author(s): Benedikt Bläsi; Oliver Höhn; Hubert Hauser; Nico Tucher; Romain Cariou; Jan Benick; Frank Feldmann; Paul Beutel; David Lackner; Gerald Siefer; Stefan W. Glunz; Andreas W. Bett; Frank Dimroth; Martin Hermle
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Paper Abstract

Silicon based multi-junction solar cells are a promising option to overcome the theoretical efficiency limit of a silicon solar cell (29.4%). With III-V semiconductors, high bandgap materials applicable for top cells are available. For the application of such silicon based multi-junction devices, a full integration of all solar cell layers in one 2-terminal device is of great advantage. We realized a triple-junction device by wafer-bonding two III-V-based top cells onto the silicon bottom cell. However, in such a series connected solar cell system, the currents of all sub-cells need to be matched in order to achieve highest efficiencies. To fulfil the current matching condition and maximise the power output, photonic structures were investigated. The reference system without photonic structures, a triple-junction cell with identical GaInP/GaAs top cells, suffered from a current limitation by the weakly absorbing indirect semiconductor silicon bottom cell. Therefore rear side diffraction gratings manufactured by nanoimprint lithography were implemented to trap the infrared light and boost the solar cell current by more than 1 mA/cm2. Since planar passivated surfaces with an additional photonic structure (i.e. electrically planar but optically structured) were used, the optical gain could be realized without deterioration of the electrical cell properties, leading to a strong efficiency increase of 1.9% absolute. With this technology, an efficiency of 33.3% could be achieved.

Paper Details

Date Published: 5 June 2018
PDF: 11 pages
Proc. SPIE 10688, Photonics for Solar Energy Systems VII, 1068803 (5 June 2018); doi: 10.1117/12.2307831
Show Author Affiliations
Benedikt Bläsi, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Oliver Höhn, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Hubert Hauser, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Nico Tucher, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Albert-Ludwigs-Univ. (Germany)
Romain Cariou, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Jan Benick, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Frank Feldmann, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Albert-Ludwigs-Univ. (Germany)
Paul Beutel, Fraunhofer-Institut für Solare Energiesysteme (Germany)
David Lackner, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Gerald Siefer, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Stefan W. Glunz, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Albert-Ludwigs-Univ. (Germany)
Andreas W. Bett, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Frank Dimroth, Fraunhofer-Institut für Solare Energiesysteme (Germany)
Martin Hermle, Fraunhofer-Institut für Solare Energiesysteme (Germany)


Published in SPIE Proceedings Vol. 10688:
Photonics for Solar Energy Systems VII
Ralf B. Wehrspohn, Editor(s)

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