Deep Level Transient Spectroscopy (DLTS) has been applied to Metal-Oxide-Semiconductor (MOS) capacitors fabricated on crystalline silicon n-and p-type substrates, with a SiO 2 or a SiO 2 /SiN x passivation stack, covered by an Al gate. It is shown that similar interface state distributions are obtained in both cases, from which it is concluded that the SiN x deposition does not degrade the interface. It is also shown that a rather large density of dangling bond defects is present at the Si/SiO 2 interface, which is related to the absence of a post metallization forming gas annealing.

Low frequency direct plasma-enhanced chemical vapor deposited Si–SiNx interface properties with and without NH3 plasma pretreatment, with and without rapid thermal annealing (RTA) have been investigated with deep-level transient spectroscopy (DLTS) on both n- and p-type monocrystalline silicon samples. It is shown that four different defect states are identified at the Si–SiNx interface. Energy-dependent electron and hole capture cross sections were also measured by small-pulse DLTS. Samples with plasma NH3 pretreatment and RTA show the lowest DLTS signals, which suggest the lowest overall interface states density. Moreover, SiNx with RTA passivates interface states more efficiently in n-type Si compared with p-type Si; also the deep-level parameters change in n-type Si but not in p-type Si. The combination of plasma NH3 pretreatment and RTA is suggested for application in the solar cell fabrication.

N‐type back‐junction back‐contact (BJ–BC) silicon solar cells have been successfully introduced in industry by Sunpower with efficiencies up to 23.4% and are being investigated by several research groups. For such n‐type bulk Si solar cells, the formation of the p+ emitter is still an issue. A traditional method is boron diffusion, which needs high temperature processes to form the emitter and to remove the silicate glass boron skin. In recent years, people have shown excellent results on n‐type front contact rear junction cells with a screen‐printed Al‐alloyed emitter. In this work, we demonstrate the use of such emitters on n‐type BJ–BC silicon solar cells. Different pitch sizes and emitter fractions have been studied. Clear trends of the short‐circuit current densities have been observed. Light beam induced current technique is used to investigate this phenomenon. Different front surface field (FSF) profiles were applied to our cells. The shallower FSF with a lower surface doping concentration results in lower front surface recombination, which results in the best cell performance. Efficiencies of 19.1% under 1 Sun on BJ–BC solar cells with an aperture area of 2 cm × 2 cm have been achieved on n‐type FZ and CZ silicon wafers. Good short‐circuit current densities and fill factors have been obtained. Compared to the boron‐diffused emitter BJ–BC solar cells, relatively low open‐circuit voltages were obtained. Better quality emitter with more effective cleaning process steps and passivation layers have been developed, to result in a further increase in cell efficiency in the future work. Copyright © 2010 John Wiley & Sons, Ltd.