Seed layer printed contact formation for highly doped boron emitters of n-type silicon solar cells with front side junction
Seed layer printed, fired and plated front side contacts are an industrial feasible high-efficiency technique for p-type silicon solar cells with a front side phosphorous-doped emitter. In this work we studied such a contact formation for boron-doped emitters of n-type silicon solar cells by applying a jet printed silver seed layer. The contact formation was investigated on shallow, industrial-type as well as on deep, high-efficiency-type emitters by means of specific contact resistance measurements for different firing conditions. Moreover, the emitter shunting has been studied by firing p+nn+ test structures at temperatures between 700 and 850 °C. Based on the observed results, p+nn+ solar cells have been fabricated, featuring the shallow boron emitter and an unpassivated, fully metalized phosphorous-doped back surface field. Conversion efficiencies up to 20.5% and fill factors of 80.8% could be achieved, demonstrating the effective contact formation to the boron-doped emitter on the device level.