Silicon dominates the photovoltaic industry but the conversion efficiency of silicon single-junction solar cells is intrinsically constrained to 29.4%, and practically limited to around 27%. It is possible to overcome this limit by combining silicon with high-bandgap materials, such as III–V semiconductors, in a multi-junction device. Significant challenges associated with this material combination have hindered the development of highly efficient III–V/Si solar cells. Here, we demonstrate a III–V/Si cell reaching similar performances to standard III–V/Ge triple-junction solar cells. This device is fabricated using wafer bonding to permanently join a GaInP/GaAs top cell with a silicon bottom cell. The key issues of III–V/Si interface recombination and silicon's weak absorption are addressed using poly-silicon/SiO x passivating contacts and a novel rear-side diffraction grating for the silicon bottom cell. With these combined features, we demonstrate a two-terminal GaInP/GaAs//Si solar cell reaching a 1-sun AM1.5G conversion efficiency of 33.3%.

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Change history

  • 25 June 2018

    In the version of this Article originally published, in the ‘Rear-side light trapping’ paragraph of the Methods section, the values of depth and fill factor were incorrectly given as 350 nm and 50%, respectively; instead, the values should have read 250 nm and 60%. This has now been corrected.

  • 03 May 2018

    In the version of this Article originally published, in the legend in Fig. 5a, the blue, green and red lines were incorrectly labelled as GaAs, Si and GaInP, respectively; instead, the labels should have read, respectively, GaInP, GaAs and Si. This has now been corrected.


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The authors thank the Fraunhofer ISE employees E. Oliva, A. Schütte, R. Koch, M. Graf, E. Schäffer, M. Schachtner, E. Fehrenbacher, A. Wekkeli, K. Wagner, S. Stättner, R. Freitas, A. Lösel, A. Leimenstoll, F. Schätzle and V. Klinger for helping with device processing and characterization. We also thank T. Höche and C. Patzig from Fraunhofer IMWS for the TEM studies. We further acknowledge financial support through the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie HISTORIC grant agreement no. 655272 and the German Ministry for Economic Affairs and Energy through the project PoTaSi (no. 0324247). The development of the Si bottom cell received funding through the EU project NanoTandem under grant agreement no. 641023. This article reflects only the authors' view and the funding agency is not responsible for any use that may be made of the information it contains.

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Author notes

    • Romain Cariou

    Present address: Université Grenoble Alpes, CEA, LITEN, INES, Grenoble, France


  1. Fraunhofer Institute for Solar Energy Systems ISE, Freiburg, Germany

    • Romain Cariou
    • , Jan Benick
    • , Frank Feldmann
    • , Oliver Höhn
    • , Hubert Hauser
    • , Paul Beutel
    • , Benedikt Bläsi
    • , David Lackner
    • , Martin Hermle
    • , Gerald Siefer
    • , Stefan W. Glunz
    • , Andreas W. Bett
    •  & Frank Dimroth
  2. Laboratory for Photovoltaic Energy Conversion, University of Freiburg, Freiburg, Germany

    • Frank Feldmann
    •  & Stefan W. Glunz
  3. EV Group E. Thallner GmbH, St Florian am Inn, Austria

    • Nasser Razek
    •  & Markus Wimplinger


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R.C. carried out experiments in the laboratory, theoretical modelling and evaluation of the data; R.C. and J.B. led the process development and optimization. F.F., M.H. and S.W.G. developed the passivating and carrier-selective contact Si bottom cell; S.W.G. also performed the analysis of spectrum utilization in Fig. 5d. P.B. improved the III–V layer structure and performed the epitaxy growth. D.L. performed band structure simulations and coordinated the epitaxy research. N.R. performed the wafer bonding and coordinated the TEM analysis; M.W. supervised the wafer bonding collaboration and led the design of the EVG580 ComBond cluster tool. O.H. and H.H. proposed the idea of the specific rear-side diffraction grating and developed and fabricated the crossed grating together. B.B. supported the understanding and fine-tuning of the rear-side grating and coordinated the photonic light-trapping research. G.S. supervised the cell calibration and ensured the accuracy of the measurements. A.W.B. supported discussions and editing of the manuscript and F.D. developed the concept of two-terminal III–V//Si tandem cells by direct wafer bonding and contributed to many aspects of the cell design and process optimization. All co-authors participated in the discussions and improvements of this manuscript.

Competing interests

The authors N. Razek and M. Wimplinger are employed by EV Group E. Thallner GmbH, 4782 St Florian am Inn, Austria, which produces the wafer bonding machine used in this study.

Corresponding author

Correspondence to Romain Cariou.

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