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Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

Nature Energy volume 2, Article number: 17062 (2017) Cite this article

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Abstract

For crystalline-silicon solar cells, voltages close to the theoretical limit are nowadays readily achievable when using passivating contacts. Conversely, maximal current generation requires the integration of the electron and hole contacts at the back of the solar cell to liberate its front from any shadowing loss. Recently, the world-record efficiency for crystalline-silicon single-junction solar cells was achieved by merging these two approaches in a single device; however, the complexity of fabricating this class of devices raises concerns about their commercial potential. Here we show a contacting method that substantially simplifies the architecture and fabrication of back-contacted silicon solar cells. We exploit the surface-dependent growth of silicon thin films, deposited by plasma processes, to eliminate the patterning of one of the doped carrier-collecting layers. Then, using only one alignment step for electrode definition, we fabricate a proof-of-concept 9-cm2 tunnel-interdigitated back-contact solar cell with a certified conversion efficiency >22.5%.

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Figure 1: The tunnel-IBC solar-cell concept and its low-complexity fabrication process.
Figure 2: Interband-tunnelling passivating contact for electrons.
Figure 3: The doped Si:H bilayer microstructure.
Figure 4: Best tunnel-IBC solar cell.

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Acknowledgements

This work was supported by the Swiss Commission for Technology and Innovation (CTI) by the Swiss Federal Office for Energy (SFOE), and by the Fonds National Suisse Reequip Program. The authors thank Meyer Burger Research for scientific partnership and financial support; D. Lachenal and B. Strahm for support and collaboration in back-contacted silicon heterojunction solar-cell development; J. Hermans and Meyer Burger B.V. for the support in inkjet printing; M. Pickrell and SunChemicals for supplying the hot melt; the Academic Writing Services at KAUST for text editing; M. J. Lehmann, N. Badel and H. Watanabe at EPFL and CSEM for their support in back-end processing; and A. Hessler at EPFL and CIME for the TEM observations.

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Authors and Affiliations

  1. École Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin Film Electronics Laboratory, Rue de la Maladière 71b, CH-2000 Neuchâtel, Switzerland

    Andrea Tomasi, Quentin Jeangros, Jan Haschke, Johannes Peter Seif, Stefaan De Wolf & Christophe Ballif

  2. Centre Suisse d’Électronique et de Microtechnique (CSEM), PV-Center, Rue Jaquet-Droz 1, CH-2002 Neuchâtel, Switzerland

    Bertrand Paviet-Salomon, Gabriel Christmann, Loris Barraud, Antoine Descoeudres, Sylvain Nicolay, Matthieu Despeisse & Christophe Ballif

  3. Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland

    Quentin Jeangros

  4. King Abdullah University of Science and Technology (KAUST), KAUST Solar Center (KSC), Thuwal 23955-6900, Saudi Arabia

    Stefaan De Wolf

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  1. Andrea Tomasi
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Contributions

A.T., B.P.-S., M.D. and C.B. conceived the idea. A.T. designed the experiments and carried out the device fabrication in collaboration with B.P.-S. Q.J. carried out the TEM observations. L.B. and A.D. developed the a-Si:H(i) passivating films. J.P.S. contributed to the development of the doped Si:H thin-film materials. S.N. and G.C. developed and deposited the TCO material. J.H. and S.D.W. contributed to the definition and presentation of the paper contents. S.D.W., M.D. and C.B. discussed the results and organized the research. A.T. wrote the paper, and all other authors provided feedback.

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Correspondence to Andrea Tomasi.

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Supplementary Notes 1–5, Supplementary Figures 1–6, Supplementary Tables 1–5, Supplementary References. (PDF 1689 kb)

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Tomasi, A., Paviet-Salomon, B., Jeangros, Q. et al. Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth. Nat Energy 2, 17062 (2017). https://doi.org/10.1038/nenergy.2017.62

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