Isolating p- and n-Doped Fingers With Intrinsic Poly-Si in Passivated Interdigitated Back Contact Silicon Solar Cells

Matthew B. Hartenstein, William Nemeth, Vincenzo Lasalvia, Steve Harvey, Harvey Guthrey, San Theingi, Matthew Page, David L. Young, Paul Stradins, Sumit Agarwal

Research output: Contribution to journalArticlepeer-review

11 Scopus Citations


Polycrystalline silicon on silicon oxide (poly-Si/SiOx) passivating contacts enable ultrahigh-efficiency interdigitated back contact silicon solar cells. To prevent shunt between n- and p-type-doped fingers, an insulating region is required between them. We evaluate the use of intrinsic poly-Si for this isolation region. Interdigitated fingers were formed by plasma deposition of doped hydrogenated amorphous silicon through mechanically aligned shadow masks on top of a full-area intrinsic hydrogenated amorphous silicon (a-Si:H) layer. High-temperature annealing then crystallized the a-Si:H to poly-Si and drove in the dopants. Two mechanisms were identified which cause contamination of the intrinsic poly-Si gap during processing. During deposition of doped fingers, we show using secondary ion mass spectrometry and conductivity measurements that the intrinsic gap becomes contaminated by doped a-Si:H tails several nanometers thick to concentrations of ∼1020 cm-3. Another source of contamination occurs during high-temperature annealing, where dopants desorb from doped regions and readsorb onto intrinsic a-Si:H. Both pathways reduce the resistivity of the intrinsic gap from ∼105 to ∼10-1 Ω·cm. We show that plasma etching of the a-Si:H surface before crystallizing with a capping layer can eliminate the contamination of the intrinsic poly-Si, maintaining a resistivity of ∼105 Ω·cm. This demonstrates masked plasma deposition as a dopant patterning method for Si solar cells.

Original languageAmerican English
Article number9199536
Pages (from-to)1574-1581
Number of pages8
JournalIEEE Journal of Photovoltaics
Issue number6
StatePublished - Nov 2020

Bibliographical note

Publisher Copyright:
© 2011-2012 IEEE.

NREL Publication Number

  • NREL/JA-5900-76547


  • Interdigitated back contact (IBC)
  • passivating contacts
  • silicon solar cells


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