New peer-reviewed article in ACS Applied Materials and Interfaces

A new article, entitled “In Situ Reflectometry and Diffraction Investigation of the Multiscale Structure of p-Type Polysilicon Passivating Contacts for c-Si Solar Cells” was published in the peer-reviewed journal Applied Materials and Interfaces of ACS.

One key objective of the SLICE project is to develop novel methodologies to elucidate the interrelation between the functional properties of poly-Si contacts (especially surface passivation) and their fabrication process. In this article, we describe the application of X-ray reflectometry (XRR) and diffraction (XRD) to poly-Si passivating contacts. In short, these techniques allow for probing the thickness, density and crystallinity of thin films in multilayer structures. More particularly, here, we applied in situ XRR and XRD while annealing samples from room temperature to 900 °C, which was never reported before.

These investigations enabled us to monitor the structural evolution of both the poly-Si layer and the buried SiOx interface during annealing up to 900 °C. Firstly, we could observe the disruption of the thin SiOx layer from a temperature of 850 °C, which correlates well with a regime in which the surface passivation provided by the poly-Si contact significantly degrades. This result confirms that the disruption of the thin SiOx is most likely involved in the loss of surface passivation observed at temperatures higher than 850 °C . We could also observe two distinct regimes during annealing for the top poly-Si layer. First, for temperatures from 200 °C up to 500 °C, the poly-Si layer becomes denser and thinner, most likely due to hydrogen out-gassing from the layer. Second, from 800 °C, the layer starts crystallizing, which is not associated to any significant changes of the layer’s macro structure (i.e., density and thickness).

Overall, our results emphasize the impact of high-temperature thermal budgets on the final properties of poly-Si contacts, and thus the importance of ensuring a good control of such high-temperature processes during the fabrication of c-Si solar cells integrating such contacts. This study also demonstrates the robustness of combining different X-ray elastic scattering techniques (here XRR and GIXRD) to unravel the multiscale structural evolution of poly-Si contacts during high-temperature processes.

The full paper is available for reading here.

Audrey Morisset, Theodosios Famprikis, Franz-Josef Haug, Andrea Ingenito, Christophe Ballif, and Lars J. Bannenberg, ACS Applied Materials & Interfaces 2022 14 (14), 16413-16423, DOI: 10.1021/acsami.2c01225.