Isolating p- and n-Doped Fingers With Intrinsic Poly-Si in Passivated Interdigitated Back Contact Silicon Solar Cells
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 ~10^20 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 ~10^5 to ~10^-1 O 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 ~10^5 O cm. This demonstrates masked plasma deposition as a dopant patterning method for Si solar cells.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
- DOE Contract Number:
- DE-AC36-08GO28308
- OSTI ID:
- 1721755
- Report Number(s):
- NREL/JA-5900-76547; MainId:7221; UUID:9fb4fcfe-128d-48e1-8c7b-cf0ba527f295; MainAdminID:18851
- Journal Information:
- IEEE Journal of Photovoltaics, Vol. 10, Issue 6
- Country of Publication:
- United States
- Language:
- English
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