Performance of III-V Solar Cells Grown on Reformed Mesoporous Ge Templates

Alessandro Cavalli, Noor Alkurd, Steve Johnston, David Diercks, Dennice Roberts, Brett Ley, John Simon, David Young, Corinne Packard, Aaron Ptak

Research output: Contribution to journalArticlepeer-review

8 Scopus Citations


We demonstrate a solar cell on reformed porous Ge with an efficiency of 7.7%. We generate mesopores in (100) Ge by bipolar electrochemical etching and anneal them at high temperature. The pores coalesce deep in the structure rather than at the surface as desired, although resulting in coarse superficial morphology unsuitable for device growth. To combat this issue, we developed a surface treatment involving an HBr dip, annealing at 415°C, and a postannealing ultrasonic De-ionized water dip to improve the surface structure, resulting in a smoother reformed surface on which we grow a GaInAs solar cell. The structure retains embedded pores after growth and the transitions between Ge and III-V layers are distinct. The solar cell fabricated using the improved coalescence has an efficiency of 4.5%. The efficiency improves to 7.7% by isolating the rest of the device from three limiting localized shunt areas. Protruding defects in the porous Ge and III-V layers still limit the performance, but this work establishes a step toward the technical viability of this exfoliation approach, showing decent efficiency if protruding defects can be removed or reduced.

Original languageAmerican English
Pages (from-to)337-343
Number of pages7
JournalIEEE Journal of Photovoltaics
Issue number1
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© 2011-2012 IEEE.

NREL Publication Number

  • NREL/JA-5900-80923


  • III-V solar cells
  • Photovoltaics
  • Porosification
  • Substrate reuse


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