A Comprehensive Study of the Performance of Silicon Screen-Printed Solar Cells Fabricated with Belt Furnace Emitters
Upadhyaya, A. D.
Kalejs, Juris P.
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ABSTRACT: In this paper we report on the screen-printed solar cells fabricated on three types of silicon materials; float zone (FZ), HEM multicrystalline and EFG ribbon with POCl3 and belt furnace diffused emitters. The belt furnace diffused emitters involved one- and two-side phosphorus spin-on to assess the contaminating effect of the IR belt. The solar cells with POCl3 emitters and co-firing of screen-printed contacts produced efficiencies of 17.3% on FZ, 16.4% on HEM and 15.5% on EFG ribbon silicon. Solar cells with two-side phosphorus emitters diffused on the belt furnace, produced efficiencies of 17.2%, 16.0%, and 15.1%, respectively, on FZ, HEM and EFG ribbon silicon. However, appreciably lower efficiencies of 15.5%, 15.5%, and 14.1% were obtained, respectively, on FZ, HEM and EFG ribbon silicon for belt-diffused emitters with only one-side phosphorus spin-on with the other side on the belt. This difference in efficiency is reflected in Voc loss for the belt-diffused emitters compared to the POCl(3) emitter cells. The IQE measurements supported that solar cells with belt-diffused emitter with two-side phosphorus spin-on and POCl(3) emitter cells had comparable Jsc. However, the cell with phosphorus spin-on on one-side gave much lower IQE because of poor bulk lifetime or the contamination due to direct contact with the belt. These results indicate that the belt emitters can account for appreciable loss in the performance of the many current commercial cells; however, this loss can be regained by applying phosphorus dopant to both side of the wafer.