Raising the one-sun conversion efficiency of III–V/Si solar cells to 32.8% for two junctions and 35.9% for three junctions


Today’s dominant photovoltaic technologies rely on single-junction devices, which are approaching their practical efficiency limit of 25–27%. Therefore, researchers are increasingly turning to multi-junction devices, which consist of two or more stacked subcells, each absorbing a different part of the solar spectrum. Here, we show that dual-junction III–V//Sidevices with mechanically stacked, independently operated III–V and Si cells reach cumulative one-sun efficiencies up to 32.8%. Efficiencies up to 35.9% were achieved when combining a GaInP/GaAs dual-junction cell with a Si single-junction cell. These efficiencies exceed both the theoretical 29.4% efficiency limit of conventional Si technology and the efficiency of the record III–V dual-junction device (32.6%), highlighting the potential of Si-based multi-junction solar cells. However, techno-economic analysis reveals an order-of-magnitude disparity between the costs for III–V//Si tandem cells and conventional Si solar cells, which can be reduced if research advances in low-cost III–V growth techniques and new substrate materials are successful.

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Figure 1: Design of the III–V//Si tandem solar cells.
Figure 2: Photovoltaic performance of the mechanically stacked III–V//Si 2J devices.
Figure 3: Design of the four-terminal GaInP/GaAs//Si triple-junction solar cell.
Figure 4: Photovoltaic performance of our best four-terminal GaInP/GaAs//Si triple-junction solar cell.
Figure 5: Fabrication process flow considered in our techno-economic analysis (near term).
Figure 6: Modelled costs of the III–V//Si dual-junction solar cells assuming an increase in tandem-cell efficiency from 30% (near term) to 32% (mid term) and 35% (long term).


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S.E. acknowledges support by a Marie Skłodowska-Curie Individual Fellowship from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No: 706744, action acronym: COLIBRI). Funding for this work at NREL was provided by DOE through EERE contract SETP DE-EE00030299 and under Contract No. DE-AC36-08GO28308 and by Laboratory-Directed Research and Development funds. At NREL, W. Olavarria performed III–V MOVPE growth, M. Young processed the III–V devices, and A. Hicks provided some illustrations. At CSEM, funding was provided by the Swiss National Science Foundation (Nanotera and PNR70 programmes) and by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 641864. N. Badel from CSEM performed the screen printing and F. Debrot from CSEM the wafer texturing. We would like to thank T. Moriarty of NREL’s cell certification laboratory for careful and thorough testing of several sets of tandem-cell devices.

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S.E. developed the tandem-cell design and, together with A.T., led the tandem-cell development and optimization. D.L.Y. and J.S.W. contributed to initial stages of tandem-cell design development. J.F.G., M.A.S. and A.T. developed the III–V top-cell layer structure and optimized the growth conditions. A.T. characterized the III–V solar cells, and is the project PI at NREL. C.A. and M.D. led the Si-bottom-cell fabrication at CSEM and C.A. provided characterization of the Si cells before stacking. S.E., M.S. and A.T. carried out the tandem-cell stacking process and the uncertified characterization. L.B. and A.D. from CSEM assisted with the Si-bottom-cell fabrication and optimization. C.B. is the heading the SHJ and tandem-cell activities at CSEM. The cost analysis was performed by K.H., T.R. and M.W. from NREL and discussed in detail with A.T., S.E., C.A., M.D. and C.B. S.E. wrote the manuscript, and all other authors provided feedback.

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Correspondence to Stephanie Essig.

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Supplementary Table 1 and Supplementary Figures 1–3. (PDF 768 kb)

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Essig, S., Allebé, C., Remo, T. et al. Raising the one-sun conversion efficiency of III–V/Si solar cells to 32.8% for two junctions and 35.9% for three junctions. Nat Energy 2, 17144 (2017). https://doi.org/10.1038/nenergy.2017.144

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