Tabula Rasa for n-Cz Silicon-Based Photovoltaics

Vincenzo LaSalvia, Amanda Youssef, Mallory A. Jensen, Erin E. Looney, William Nemeth, Matthew Page, Wooseok Nam, Tonio Buonassisi, Paul Stradins

Research output: Contribution to journalArticlepeer-review

11 Scopus Citations

Abstract

High-temperature annealing, known as Tabula Rasa (TR), proves to be an effective method for dissolving oxygen precipitate nuclei in n-Cz silicon and makes this material resistant to temperature-induced and process-induced lifetime degradation. Tabula Rasa is especially effective in n-Cz wafers with oxygen concentration >15 ppma. Vacancies, self-interstitials, and their aggregates result from TR as a metastable side effect. Temperature-dependent lifetime spectroscopy reveals that these metastable defects have shallow energy levels ~0.12 eV. Their concentrations strongly depend on the ambient gases during TR because of an offset of the thermal equilibrium between vacancies and self-interstitials. However, these metastable defects anneal out at typical cell processing temperatures ≥850°C and have little effect on the bulk lifetime of the processed cell structures. Without dissolving built-in oxygen precipitate nuclei, high-temperature solar cell processing severely degrades the minority carrier lifetimes to below 0.1 millisecond, while TR-treated n-Cz wafers after the cell processing steps exhibit carrier lifetimes above 2.2 milliseconds.

Original languageAmerican English
Pages (from-to)136-143
Number of pages8
JournalProgress in Photovoltaics: Research and Applications
Volume27
Issue number2
DOIs
StatePublished - 2019

Bibliographical note

Publisher Copyright:
© 2018 John Wiley & Sons, Ltd.

NREL Publication Number

  • NREL/JA-5900-71883

Keywords

  • bulk lifetime
  • diffused boron emitter
  • intrinsic point defects
  • n-type Czochralski
  • oxygen precipitation
  • photovoltaics
  • Tabula Rasa
  • thermally induced degradation

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