THE USE OF ALUMINIUM SPIKING FOR FORMING SMALL AREA CONTACTS FOR SILICON SOLAR CELLS

摘要

This paper presents the progress of developing the contacting technique that uses aluminum spiking to penetrate silicon dioxide in localized regions to form small area rear contacts for buried contact solar cells. The aluminum layer can be further utilized to mediate solid phase epitaxial growth of p~+ silicon at the pinhole contact interface. As part of the optimization, a conversion efficiency of 17.4% under one-sun AM1.5G illuminations at 25℃ has been achieved with improvements in fill factor; open circuit voltage and short circuit currents. These cells only have rudimentary antireflection coating with no texturing. Study indicated the heat treatments required for the formation of pinhole contacts and the epitaxial growth of p~+ silicon have a detrimental effect on the passivation quality of the oxide layer even in regions where no spiking has occurred. Recommendations for future improvement of the technique are presented in this paper. As part of the physical characterization of the pinhole contacts, cross sectional view of the Al/SiO_2/Si interaction at elevated temperature has been realized for the first time using focused ion beam microcopy. The technique developed by the authors has also been used by other researchers for third generation photovoltaic research at the University of New South Wales.