Hydrogenation Mechanisms of Poly-Si/SiOx Passivating Contacts by Different Capping Layers

Matthew Young, Mowafak Al-Jassim, Thien Truong, Di Yan, Wenhao Chen, Mike Tebyetekerwa, Andres Cuevas, Daniel Macdonald, Hieu Nguyen

Research output: Contribution to journalArticlepeer-review

25 Scopus Citations

Abstract

Herein, posttreatment techniques of phosphorus-doped poly-Si/SiOx passivating contacts, including forming gas annealing (FGA), atomic layer deposition (ALD) of hydrogenated aluminum oxide (AlOx:H), and plasma-enhanced chemical vapor deposition (PECVD) of hydrogenated silicon nitride (SiNx:H), are investigated and compared in terms of their application to silicon solar cells. A simple FGA posttreatment produces a significant increase in the implied open circuit voltage (iVoc) and the effective minority-carrier lifetime (τeff) of high-resistivity crystalline Si (c-Si) samples, whereas low-resistivity samples show a minimal change. Treatment by means of AlOx:H and/or SiNx:H followed by postdeposition FGA results in a universal increase in τeff and iVoc for all substrate resistivities (as high as 12.5 ms and 728 mV for 100 Ω cm and 5.4 ms and 727 mV for 2 Ω cm n-type c-Si substrates). In addition, both the FGA and AlOx:H + FGA techniques can inject sufficient hydrogen into the samples to passivate defects at the SiOx/c-Si and poly-Si/SiOx interfaces. However, this hydrogen concentration is insufficient to neutralize both the nonradiative defects inside the poly-Si films and dangling bonds associated with the amorphous Si phase present in them. The hydrogen injected by the SiNx:H + FGA technique can passivate both the interfaces and the defects and dangling bonds within the poly-Si film. These results are confirmed by low-temperature photoluminescence spectroscopy, Fourier transform infrared spectroscopy, and dynamic secondary-ion mass spectrometry measurements.

Original languageAmerican English
Article number1900476
Number of pages6
JournalSolar RRL
Volume4
Issue number3
DOIs
StatePublished - 2020

Bibliographical note

Publisher Copyright:
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

NREL Publication Number

  • NREL/JA-5K00-75263

Keywords

  • aluminum oxide
  • doped polycrystalline silicon
  • forming gas anneal
  • hydrogenation
  • passivating contacts
  • silicon nitride

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