In Situ Reflectometry and Diffraction Investigation of the Multiscale Structure of p-Type Polysilicon Passivating Contacts for c-Si Solar Cells

Audrey Morisset*, Theodosios Famprikis, Franz Josef Haug, Andrea Ingenito, Christophe Ballif, Lars J. Bannenberg

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

The integration of passivating contacts based on a highly doped polycrystalline silicon (poly-Si) layer on top of a thin silicon oxide (SiOx) layer has been identified as the next step to further increase the conversion efficiency of current mainstream crystalline silicon (c-Si) solar cells. However, the interrelation between the final properties of poly-Si/SiOx contacts and their fabrication process has not yet been fully unraveled, which is mostly due to the challenge of characterizing thin-film stacks with features in the nanometric range. Here, we apply in situ X-ray reflectometry and diffraction to investigate the multiscale (1 Å-100 nm) structural evolution of poly-Si contacts during annealing up to 900 °C. This allows us to quantify the densification and thinning of the poly-Si layer during annealing as well as to monitor the disruption of the thin SiOx layer at high temperature >800 °C. Moreover, results obtained on a broader range of thermal profiles, including firing with dwell times of a few seconds, emphasize the impact of high thermal budgets on poly-Si contacts' final properties and thus the importance of ensuring a good control of such high-temperature processes when fabricating c-Si solar cells integrating such passivating contacts. Overall, this study demonstrates the robustness of combining different X-ray elastic scattering techniques (here XRR and GIXRD), which present the unique advantage of being rapid, nondestructive, and applicable on a large sample area, to unravel the multiscale structural evolution of poly-Si contacts in situ during high-temperature processes.

Original languageEnglish
Pages (from-to)16413-16423
JournalACS Applied Materials and Interfaces
Volume14
Issue number14
DOIs
Publication statusAccepted/In press - 2022

Keywords

  • annealing
  • c-Si solar cells
  • in situ monitoring
  • passivating contacts
  • poly-Si
  • SiO
  • X-ray reflectometry

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