The choice of silicon wafer for the production of low-cost rear-contact solar cells

SunPower manufactures high-efficiency rear-contact solar cells. To offer these cells at a competitive price, SunPower requires a source of low-cost wafers with the necessary lifetime, thickness and resistivity to attain a cell efficiency of at least 20%. With simulation and experiment, this paper investigates how each of these parameters affects the efficiency of SunPower's low-cost, rear-contact solar cell. It concludes that the cell efficiency approaches an optimum when the wafers have (i) a lifetime in excess o 1 ms, (ii) a thickness of 160-280 /spl mu/m, and (iii) a resistivity of 2-10 /spl Omega/cm (n-type). The requirement of the high lifetime restricts the wafer choice to FZ, PV-FZ or n-type Cz; but the wide tolerance on wafer thickness and resistivity help lower the wafer cost by maximizing the yield from a silicon ingot.

[1]  P. Altermatt,et al.  High efficiency PERT cells on n-type silicon substrates , 2002, Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference, 2002..

[2]  L. Jensen,et al.  Float-zone silicon for high volume production of solar cells , 2003, 3rd World Conference onPhotovoltaic Energy Conversion, 2003. Proceedings of.

[3]  R. Hezel,et al.  Investigation of carrier lifetime instabilities in Cz-grown silicon , 1997, Conference Record of the Twenty Sixth IEEE Photovoltaic Specialists Conference - 1997.