Nitric acid pretreatment for the passivation of boron emitters for n -type base silicon solar cells

We have developed a simple method to passivate industrially produced boron-doped emitters for n -type base silicon solar cells using an ultrathin ( ∼ 1.5 nm ) silicon dioxide layer between the silicon emitter and the silicon nitride antireflection coating film. This ultrathin oxide is grown at room temperature by soaking the silicon wafers in a solution of nitric acid prior to the deposition of the silicon nitride antireflection coating film. The n -type solar cells processed in such a way demonstrate a conversion efficiency enhancement of more than 2% absolute over the solar cells passivated without the silicon dioxide layer.