18% Large Area Screen-Printed Solar Cells on Textured MCZ Silicon with High Sheet Resistance Emitter

In this paper we report on high efficiency screen-printed 49 cm2 solar cells fabricated on randomly textured float zone (1.2 ¿-cm) and magnetic Czochralski (MCZ) silicon with resistivities of 1.2 and 4.8 ¿-cm, respectively. A simple process involving POCl3 diffused emitters, low frequency PECVD silicon nitride deposition, Al back contact print, Ag front grid print followed by co-firing of the contacts and forming gas anneal produced efficiencies of 17.6% on 1.2 ¿-cm textured float Zone Si, 17.9% on 1.2 ¿-cm MCZ Si and 18.0% on 4.8 ¿-cm MCZ Si. A combination of high sheet resistance emitter (~95 ¿-/¿) and the surface texturing resulted in a short circuit current density of 37.8 mA/cm2 in the 4.8 ¿-cm MCZ cell, 37.0 mA/cm2 in the 1.2 ¿-cm2 MCZ cell and 36.5 mA/cm2 in the 1.2 ¿-cm2 float zone cell. The open circuit voltages were consistent with the base resistivities of the two materials. The fill factors were in the range of 0.760-0.770 indicating there is considerable room for improvement. Detailed modeling and analysis is performed to explain the cell performance and provide guidelines for achieving 20% efficient screen-printed cells on MCZ Si.