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On the nature of emitter diffusion and screen-printing contact formation on nanostructured silicon surfaces

: Kafle, B.; Freund, T.; Schön, J.; Werner, S.; Lorenz, A.; Wolf, A.; Saint-Cast, P.; Clochard, L.; Duffy, E.; Hofmann, M.; Rentsch, J.


IEEE Journal of Photovoltaics 7 (2017), No.1, pp.136-143
ISSN: 2156-3381
ISSN: 2156-3403
Journal Article
Fraunhofer ISE ()
PV Produktionstechnologie und Qualitätssicherung; Photovoltaik; Silicium-Photovoltaik; Dotierung und Diffusion; Oberflächen: Konditionierung; Passivierung; Lichteinfang; Kontaktierung und Strukturierung; nanotexture; silicon; diffusion; screen-printing

In this paper, we study the impact of change in emitter diffusion profiles on the electrical characteristics of nanotextured surfaces formed by an inline plasma-less dry-chemical etching process. Our experimental results and process simulations suggest that a deeper highly doped region and a significantly higher inactive P concentration in the emitter plays a determining role in defining recombination, as well as the resistive losses in nanotextured surfaces. Low emitter saturation current densities on phosphorous-diffused surfaces are achievable after passivation with either SiNx (j0e,m in ≈ 81 fA/cm2) or AlOx/SiNx (j0e,m in ≈ 31 fA/cm2) if the emitter recombination channels are suppressed. Based upon macroscopic measurement of contact resistivity and microscopic analysis of the contact areas, we propose that the formation of numerous metal-semiconductor direct contact points on the peak and the plateaus of the nanostructures are mainly responsible for a low specific contact resistivity (ρc,m in ≈ 1.2 mΩ · cm2) achievable in these surfaces.