期刊
IEEE JOURNAL OF PHOTOVOLTAICS
卷 11, 期 4, 页码 858-865出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/JPHOTOV.2021.3062969
关键词
Silicon; Plating; Nickel; Photovoltaic cells; Metals; Programmable logic arrays; Pollution measurement; Bifacial solar cells; characterization; electroless plating; laser doping; metrology; nickel diffusion; silicon (Si) PV modeling
资金
- imec's Industrial Affiliation Program for Si-PV
- Flemish Research Partners KU Leuven
- VITO
- IMEC
- Universiteit Hasselt in the Field of Sustainable Energy and Intelligent Energy Systems
- Kuwait Foundation [CN18-15EE-01]
Contactless plating with electroless solutions can provide high-efficiency contacts with low silver content and self-alignment. However, the combination of surface activation and immersion plating with nickel can lead to decreases in V-oc and fill factor. The impact of immersion plating on the microstructure of the plated silicon surface must be carefully studied to prevent electrical degradation.
Contactless plating with electroless solutions can provide self-aligned high-efficiency contacts with very low silver content, using simple and inexpensive equipment. With prior surface activation, it can even be used to metallize both sides of bifacial silicon solar cells simultaneously. However, we observe in such a coplating process with nickel, where surface activation is achieved by immersion plating and thickening by electroless plating, that V-oc and fill factor can sometimes significantly decrease with immersion-plating time. To understand the reason for this electrical degradation, we studied the impact of immersion plating on the microstructure of the plated silicon surface. The evolution of the Si-Ni interface was studied by scanning and transmission electron microscopies, energy-dispersive X-ray analysis, secondary ion mass spectrometry, and scanning spreading resistance microscopy. Our attention focused on metal in-diffusion, silicon roughening and etching as the origin for increased recombination. Etching was found to have a significant impact on V-oc. The thickness of N+ Si etched during Ni deposition can in fact suppress in a few locations most of the field-effect passivation underneath the contacts. This means that a thicker surface field with doping beyond 10(19)/cm(3) must be foreseen under the plated areas, or that the amount of Si lost in the reaction must be reduced. Our observations also confirm that immersion plating can hinder silicide formation and allow Ni in-diffusion, which may be a concern for reliability.
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