High-Efficiency Solar Cells Grown on Spalled Germanium for Substrate Reuse without Polishing

John Mangum, Anthony Rice, Jie Chen, Jason Chenenko, Evan Wong, Anna Braun, Steve Johnston, Harvey Guthrey, John Geisz, Aaron Ptak, Corinne Packard

Research output: Contribution to journalArticlepeer-review

18 Scopus Citations


Radical reduction of III–V device costs requires a multifaceted approach attacking both growth and substrate costs. Implementing device removal and substrate reuse provides an opportunity for substrate cost reduction. Controlled spalling allows removal of thin devices from the expensive substrate; however, the fracture-based process currently generates surfaces with significant morphological changes compared to polished wafers. 49 single junction devices are fabricated across the spalled surface of full 50 mm germanium wafers without chemo-mechanical polishing before epitaxial growth. Device defects are identified and related to morphological spalling defects—arrest lines, gull wings, and river lines—and their impact on cell performance using physical and functional characterization techniques. River line defects have the most consistent and detrimental effect on cell performance. Devices achieve a single junction efficiency above 23% and open-circuit voltage of 1.01 V, demonstrating that spalled germanium does not need to be returned to a pristine, polished state to achieve high-quality device performance.

Original languageAmerican English
Article number2201332
Number of pages12
JournalAdvanced Energy Materials
Issue number29
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© 2022 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

NREL Publication Number

  • NREL/JA-5900-82708


  • cost reduction
  • germanium
  • III–V
  • spalling
  • substrate reuse


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