TY - JOUR

T1 - Ion implantation for poly-Si passivated back-junction back-contacted solar cells

AU - Römer, Udo

AU - Peibst, Robby

AU - Ohrdes, Tobias

AU - Lim, Bianca

AU - Krügener, Jan

AU - Wietler, Tobias

AU - Brendel, Rolf

PY - 2015/3/1

Y1 - 2015/3/1

N2 - 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 J0,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 pFFimpl. are 87.3% and 84.6%, respectively. Test structures fabricated with the counterdoping process applied on a full area also exhibit excellent recombination behavior (J0,poly = 0.9 ± 1.1 fA/cm2, pFFimpl. = 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.

AB - 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 J0,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 pFFimpl. are 87.3% and 84.6%, respectively. Test structures fabricated with the counterdoping process applied on a full area also exhibit excellent recombination behavior (J0,poly = 0.9 ± 1.1 fA/cm2, pFFimpl. = 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.

KW - Back contact solar cells

KW - carrier selective contacts

KW - ion implantation

KW - photovoltaic cells

KW - solar energy

UR - http://www.scopus.com/inward/record.url?scp=85027934898&partnerID=8YFLogxK

U2 - 10.1109/jphotov.2014.2382975

DO - 10.1109/jphotov.2014.2382975

M3 - Article

AN - SCOPUS:85027934898

VL - 5

SP - 507

EP - 514

JO - IEEE journal of photovoltaics

JF - IEEE journal of photovoltaics

SN - 2156-3381

IS - 2

M1 - 7006679

ER -