High efficient N-type interdigitated back contact silicon solar cells with screen-printed al-alloyed emitter

N-type interdigitated back contact (IBC) silicon solar cells have been successfully applied industrially with high-efficiency of 23.4% by Sunpower and are being investigated by several research groups. However, the formation of 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 IBC silicon solar cells. Different pitch sizes and emitter fractions have been studied. Clear trends of the short circuit current densities were observed. Light beam induced current technique was 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 gives the lower front surface recombination, which results the best cell performance. Efficiencies of 19.1% under 1 Sun on IBC solar cells with an active area of 2 × 2 cm
²
have been achieved on n-type FZ and CZ silicon. Good short circuit current densities and fill factors have been obtained. Moreover, there is still quite some space for further improvement such as better surface cleaning after Al paste removal and better surface passivation.