20%-efficient epitaxial GaAsP/Si tandem solar cells

Shizhao Fan, Zhengshan J. Yu, Yukun Sun, William Weigand, Pankul Dhingra, Mijung Kim, Ryan D. Hool, Erik D. Ratta, Zachary C. Holman, Minjoo L. Lee

Research output: Contribution to journalArticle

Abstract

We present epitaxial 1.7 eV/1.1 eV GaAs0.75P0.25/Si tandem cells with an NREL-certified efficiency of 20.0%, enabled by a thermally stable tunnel junction interconnect along with a hydrogenated amorphous Si (a-Si:H) carrier-selective contact for the Si bottom cell. Building on these promising tandem results, we also demonstrate a 16.5%-efficient GaAs0.75P0.25 single-junction top cell on Si and a 7.78%-efficient GaAs0.75P0.25-filtered Si bottom cell (both NREL-certified) with improved short-circuit current densities. The quantum efficiency of the GaAs0.75P0.25 single-junction top cell on Si is boosted across the whole wavelength range due to the use of a higher growth temperature, indicating an improved minority-carrier diffusion length. The implementation of random pyramid texturing at the Si back surface enables improved quantum efficiency at wavelengths of 900–1200 nm, corresponding to an increase of 1.42 mA/cm2 in short-circuit current density. The improved short-circuit current densities of the sub-cells together show a pathway to >23% efficiency in a two-terminal tandem configuration.

Original languageEnglish (US)
Article number110144
JournalSolar Energy Materials and Solar Cells
Volume202
DOIs
StatePublished - Nov 2019

Keywords

  • Epitaxial III-V/Si integration
  • GaAsP
  • Light trapping
  • Metamorphic growth
  • Silicon heterojunction
  • Tandem
  • Tunnel junction

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films

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  • Cite this

    Fan, S., Yu, Z. J., Sun, Y., Weigand, W., Dhingra, P., Kim, M., Hool, R. D., Ratta, E. D., Holman, Z. C., & Lee, M. L. (2019). 20%-efficient epitaxial GaAsP/Si tandem solar cells. Solar Energy Materials and Solar Cells, 202, [110144]. https://doi.org/10.1016/j.solmat.2019.110144