Title:	Impact of Light Induced Degradation on the Performance of Atmospheric Cu Contacted PERC Solar Cells
Author(s):	S. Huneycutt, A. Ebong, K. Ankireddy, R. Dharmadasa, T. Druffel
Topic:	Silicon Materials and Cells
Subtopic:	Characterisation & Simulation of Si Cells
Event:	38th European Photovoltaic Solar Energy Conference and Exhibition
Session:	2CV.1.15
ISBN:	3-936338-78-7
Price:	0,00 EUR
Document(s):	poster

Abstract/Summary:

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Previous attempts at integrating copper (Cu) paste into the solar industry have proven to be quite daunting. This is due to the fact that Cu can readily diffuse into the silicon (Si) substrate, thereby, forming interstitial and substitutional bonds that effectively create recombination centers that drastically reduce the maximum power output of the cell. In addition, Cu tends to oxidize in the presence of natural ambient, previously forcing the need to pump pure nitrogen into a high temperature furnace during contact anneal, which is very expensive. Also, in addition to the boron-oxygen (B-O) pairs that are found in traditional silver (Ag) contact cells which promote light induced degradation (LID); it has been suggested that Cu also aids in LID. In using the screen-printable atmospheric Cu paste for the PERC cells front contact, the preliminary results have shown that Cu oxidation and diffusion have been overcome. This is buttressed by the electrical output parameters including an open circuit voltage (VOC) of 666 mV, short circuit current (ISC) of 9.4 A, fill factor (FF) of 72.1%, and efficiency of 18.5%. After the Cu contacted cells were exposed to light at 100o C for 24 hours and annealed in the dark at 200o C for 3 minutes, it was found that although the lifetime did not fully recover the VOC only decreased by 12 mV and the FF reduced by 0.6%. However, the shunt resistance (RSH) of >9000 -cm2 , JO2 of 1.2x10-8 A/cm2 , and ideality factor of 1.06 at 1 sun were obtained, which is indicative of a good solar cell. The only culprit in this cell is the series resistance, which was 1.75 -cm2 before LID and increased after the recovery anneal in the dark to 1.84 -cm2 .