Ion implantation for poly-Si passivated back-junction back-contacted solar cells

authored by: Udo Römer, Robby Peibst, Tobias Ohrdes, Bianca Lim, Jan Krügener, Tobias Wietler, Rolf Brendel
Abstract: We study ion implantation for patterned doping of back-junction back-contacted solar cells with polycrystalline-monocrystalline Si junctions. In particular, we investigate the concept of counterdoping, that is, a process of first implanting a blanket emitter and afterward locally overcompensating the emitter by applying masked ion implantation for the back surface field (BSF) species. On planar test structures with blanket implants, we measure saturation current densities J_0,poly of down to 1.0 ± 1.1 fA/cm² for wafers passivated with phosphorus-implanted poly-Si layers and 4.4 ± 1.1 fA/cm² for wafers passivated with boron-implanted poly-Si layers. The corresponding implied pseudofill factors pFF_impl. are 87.3% and 84.6%, respectively. Test structures fabricated with the counterdoping process applied on a full area also exhibit excellent recombination behavior (J_0,poly = 0.9 ± 1.1 fA/cm², pFF_impl. = 84.7%). By contrast, the samples with patterned counterdoped regions exhibit a far worse recombination behavior dominated by a recombination mechanism with an ideality factor n > 1. A comparison with the blanket-implanted test structures points to recombination in the space charge region inside the highly defective poly-Si layer. Consequently, we suggest introducing an undoped region between emitter and BSF in order to avoid the formation of p⁺/n⁺ junctions in poly-Si.
Organisation(s): Institute of Electronic Materials and Devices
Institute of Solid State Physics
External Organisation(s): Institute for Solar Energy Research (ISFH)
Type: Article
Journal: IEEE journal of photovoltaics
Volume: 5
Pages: 507-514
No. of pages: 8
ISSN: 2156-3381
Publication date: 01.03.2015
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering
Sustainable Development Goals: SDG 7 - Affordable and Clean Energy
Electronic version(s): https://doi.org/10.1109/jphotov.2014.2382975 (Access: Closed)