Polysilicon Passivating Contacts for Silicon Solar Cells: Interface Passivation and Carrier Transport Mechanism

Wenzhu Liu, Xinbo Yang, Jingxuan Kang, Shuai Li, Lujia Xu, Song Zhang, Hang Xu, Jun Peng, Feng Xie, Jui-Han Fu, Kai Wang, Jiang Liu, Areej A. Alzahrani, Stefaan De Wolf

Research output: Contribution to journalArticlepeer-review

42 Scopus citations


Polysilicon passivating contacts, consisting of a stack of tunnel-oxide and doped polysilicon layers, can simultaneously provide excellent surface passivation and low contact resistivity for silicon solar cells. Nevertheless, the microscopic interfacial characteristics of such contacts are not yet fully understood. In this work, by investigating the surface passivation evolution of polysilicon passivating contacts under increasing annealing temperatures, we unveil these characteristics. Before annealing, we find that the Si and O atoms within the tunnel-oxide layer are mostly unsaturated, whereas the O atoms introduce acceptor-like defects. These defects cause Fermi-level pinning and high carrier recombination. During annealing, we identify two distinct chemical passivation regimes driven by surface hydrogenation and oxidation. We attribute the excellent chemical passivation activated by high-temperature annealing (∼850 °C) mainly to the tunnel oxide reconstruction, which effectively reduces the acceptor-like state density. During the oxide reconstruction, we also find that subnanometer pits (rather than pinholes) are formed in the oxide. A combination of experimental and theoretical investigations demonstrates these subnanometer pits provide excellent surface passivation and efficient tunneling for majority carriers.
Original languageEnglish (US)
Pages (from-to)4609-4617
Number of pages9
JournalACS Applied Energy Materials
Issue number7
StatePublished - Jul 5 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): OSR-CRG URF/1/3383
Acknowledgements: W.L. would like to acknowledge Jiajia Ling, Dr. Jichun Ye, and Dr. Yuheng Zeng for their assistance in modeling poly-Si/SiOx passivating contact solar cell in AFORS-HET v2.5. The authors also acknowledge Yifan Dang for resistivity measurements. The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under award no. OSR-CRG URF/1/3383.


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