Optimization of Four Terminal Rear Heterojunction GaAs on Si Interdigitated Back Contact Tandem Solar Cells

Adele Tamboli, Riley Whitehead, Kaitlyn VanSant, Emily Warren, Jeronimo Buencuerpo, Michael Rienäcker, Robby Peibst, John Geisz

Research output: Contribution to journalArticlepeer-review

12 Scopus Citations

Abstract

High-efficiency, four-terminal tandem solar cells composed of thin GaAs films mechanically stacked onto interdigitated back contact silicon solar cells with a glass interlayer are demonstrated. The optimal thickness of the absorber layer of a rear heterojunction GaAs subcell for use in four terminal tandem solar cells was studied. GaAs top cells with absorber layer thicknesses of 1.5, 1.9, 2.3, 2.8, and 3.5 μm were fabricated on glass and mechanically stacked onto interdigitated back-contact Si bottom cells. All tandem cells were found to have efficiencies above 30% under the AM1.5 G spectrum demonstrating a relatively weak sensitivity to thickness in the four-terminal configuration. We found the 2.8 μm absorber layer cell to have the highest top cell and tandem cell efficiency at 26.38% and 32.57%, respectively. Optical modeling with transfer matrix method for the planar top cell and Lambertian light trapping in the textured Si subcell, along with drift-diffusion Hovel equations, were used to show photon recycling enhancement to the effective diffusion length and VOC of the top cell as a result of the low-index glass interlayer.

Original languageAmerican English
Article number183902
Number of pages5
JournalApplied Physics Letters
Volume118
Issue number18
DOIs
StatePublished - 3 May 2021

Bibliographical note

Publisher Copyright:
© 2021 Author(s).

NREL Publication Number

  • NREL/JA-5K00-79377

Keywords

  • absorber layers
  • GaAs films
  • photovoltaic
  • tandem solar cells

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