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Lead Free Ohmic Connections on High Efficiency Silicon Solar Cells
E. Skuras, G. Sempros, H. Zoubos, E. Mantzopoulou, T. Giousis, D. Anagnostopoulos, T. Makris, P. Fleming, A. Santamaria
Monocrystalline, Si Solar Cell, Pb-free, Eutectic Solder Alloys, Micro XRF
Wafer-Based Silicon Solar Cells and Materials Technology
Subtopic: Silicon Solar Cells Improvements and Innovation
Event: 32nd European Photovoltaic Solar Energy Conference and Exhibition
Session: 2AV.3.38
854 - 857
ISBN: 3-936338-41-8
Paper DOI: 10.4229/EUPVSEC20162016-2AV.3.38
0,00 EUR
Document(s): paper


In this paper, we study lead-free ohmic connections made on highly efficient mono-crystalline Si solar cells. Flat copper wires coated with either Sn(96.5%)/Ag(3.5%) or Bi(58%)/Sn(42%) eutectic alloys were soldered to the bus bars of industrially-manufactured Si cells to form environmentally friendly ohmic connections. Different combinations of preheat and soldering temperatures were tested to establish the optimum conditions for achieving low resistance ohmic contacts. Temperature uniformity along the 156x156 mm2 front surface of the preheated cells was monitored using low-cost, self-adhesive irreversible temperature labels. The electrical performance of the Si cells and their ohmic connections were evaluated from the analysis of the recorded I-V characteristic curves. Efficiencies up to 18.7% and fill factors up to 78% were deduced. Micro-XRF measurements were performed after the completion of each individual step in the process used for making the ohmic connections. Analysis of the X-ray fluorescent spectra has shown compliance with the RoHS directive.