Economic viability of thin-film tandem solar modules in the United States

  • Nature Energyvolume 3pages387394 (2018)
  • doi:10.1038/s41560-018-0126-z
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Tandem solar cells are more efficient but more expensive per unit area than established single-junction (SJ) solar cells. To understand when specific tandem architectures should be utilized, we evaluate the cost-effectiveness of different II–VI-based thin-film tandem solar cells and compare them to the SJ subcells. Levelized cost of electricity (LCOE) and energy yield are calculated for four technologies: industrial cadmium telluride and copper indium gallium selenide, and their hypothetical two-terminal (series-connected subcells) and four-terminal (electrically independent subcells) tandems, assuming record SJ quality subcells. Different climatic conditions and scales (residential and utility scale) are considered. We show that, for US residential systems with current balance-of-system costs, the four-terminal tandem has the lowest LCOE because of its superior energy yield, even though it has the highest US$ per watt (US$ W–1) module cost. For utility-scale systems, the lowest LCOE architecture is the cadmium telluride single junction, the lowest US$ W–1 module. The two-terminal tandem requires decreased subcell absorber costs to reach competitiveness over the four-terminal one.

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This works was funded in part by the National Research Foundation Singapore through the Singapore-MIT Alliance for Research and Technology, the Bay Area Photovoltaic Consortium (BAPVC) under Contract no. DE-EE0004946, the US Department of Energy under Award no. DE-EE0006707 and the National Science Foundation (NSF) and Department of Energy (DOE) under NSF CA No. EEC-1041895. Numerous peer conversations at BAPVC are noted. This work additionally benefitted greatly from the prior work of D. M. Powell and S. C. Siah.

The CdTe cost model was made independently, without contribution from or corroboration by First Solar. The CIGS cost model was made independently, without contribution from or corroboration by Siva Power.

Author information


  1. Massachusetts Institute of Technology, Cambridge, MA, USA

    • Sarah E. Sofia
    • , Jonathan P. Mailoa
    • , Tonio Buonassisi
    •  & I. Marius Peters
  2. First Solar Inc., Santa Clara, CA, USA

    • Dirk N. Weiss
  3. Siva Power, Santa Clara, CA, USA

    • Billy J. Stanbery


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S.E.S. compiled cost data and developed the cost model and analysis tools, with cost inputs and feedback contributed by D.N.W., B.J.S., I.M.P. and T.B. J.P.M. and S.E.S. performed energy-yield calculations. S.E.S. performed analysis and data visualization. I.M.P., T.B. and D.N.W. conceptualized the initial project. The manuscript was written by S.E.S. and edited by all the co-authors. I.M.P. provided lead mentorship. All the authors reviewed and approved the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Sarah E. Sofia or Tonio Buonassisi or I. Marius Peters.

Supplementary information

  1. Supplementary Information

    Supplementary Tables 1–9, Supplementary Methods, Supplementary Figure 1 and Supplementary References.