Sliver Solar Cells for Concentrator PV Systems with Concentration Ratio Below 50

This paper links together two different yet complimentary technologies: concentrator photovoltaics (CPVs) and Sliver technology. Recent research and development and commercialisation efforts in concentrator technologies have centred on high-concentration systems, encouraged by the availability of high-efficiency, multi-junction III-V cells. In contrast, little attention has been paid to the potential of systems with low-to-medium levels of concentration. Arguably, this is due to the absence of any suitable, low-cost concentrator cells, readily available at a commercial scale. Sliver technology is a candidate for the supply of commercial low-cost cells suitable for systems with concentration ratios in the range of 5–50. This can be achieved via judicious choice of cell design parameters and with only minor changes to the fabrication process suitable for 1-sun Sliver cells. Device modelling is used to show that Sliver cells are suitable for illumination intensities up to 5 W/cm2, with unavoidable emitter resistance limiting performance for higher intensities. The best cells manufactured for operation at low and medium concentration had efficiencies of 18·8% at 9 suns (above 18·6% between 5 and 15 suns) and 18·4% at 37 suns (above 18·2% between 30 and 50 suns), respectively. Incorporation of sidewall texturing and SiN anti-reflection coatings would yield efficiencies exceeding 20% for similar cells. Concentrator Sliver cells can be produced to almost any length and are perfectly bifacial, features which add significantly to their attractiveness to concentrator system designers. The availability of cheap concentrator Sliver cells could provide opportunities for new, low-cost concentrator systems, which in turn has the potential to provide a pathway to low-cost solar electricity. Copyright © 2009 John Wiley & Sons, Ltd.

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