Homogenous Voltage-Matched Strings Using Three-Terminal Tandem Solar Cells: Fundamentals and End Losses

William McMahon, Henning Schulte-Huxel, Jeronimo Buencuerpo, John Geisz, Michelle Young, Talysa Klein, Adele Tamboli, Emily Warren

Research output: Contribution to journalArticlepeer-review

13 Scopus Citations


Strings constructed from three-terminal tandem (3TT) solar cells offer the performance benefits of voltage-matching (which reduces sensitivity to spectral variation), but without the subcell voltage isolation required by four-terminal cells. However, the circuitry for a 3TT string can become complex, making circuit analysis more challenging. Here, we illustrate the essential features of 'homogenous' voltage-matched (VM) 3TT strings, for which all 3TT cells in the string are nominally identical (with the same design/doping sequence, such that they can be fabricated on the same manufacturing line). Several representative VM string configurations are explicitly considered, and used to describe the general construction of string I(V) curves. End losses intrinsic to these strings are discussed in detail, along with mitigation strategies to minimize their impact. Our analysis agrees with experimental results for eight-cell strings constructed from GaInP/GaAs 3TT devices.

Original languageAmerican English
Article number9429873
Pages (from-to)1078-1086
Number of pages9
JournalIEEE Journal of Photovoltaics
Issue number4
StatePublished - Jul 2021

Bibliographical note

Publisher Copyright:
© 2011-2012 IEEE.

NREL Publication Number

  • NREL/JA-5900-78778


  • Cell stringing
  • tandem cells
  • three-terminal
  • voltage-matched (VM)


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