The investigation on the front surface oxidation for aluminum rear emitter n-type solar cells

Since front surface field characterization is one of the crucial factors for aluminum back junction n-type cells, the emphasis of this paper is focused on the quality of this n⁺ layer. Oxidation process is wildly used for high efficiency solar cells. Higher temperature and thicker SiOx layers can provide a better passivation effect. However oxidation process can also reduce the surface concentration of phosphorus, and thicken the n⁺ layer. Both of a too low surface concentration and a thick n⁺ layer are not needed. After the optimization, the oxidation temperature and time are fixed on 900 □ and 15 min, respectively. The passivation effect is well-done; the minority lifetime of the wafers after oxidation is nearly 400 μs. And the sheet resistance of about 150 Ω/□ is better for the cells fabrication. A high open-circuit voltage of over 645 mV and a high fill factor of over 0.80 have been obtained.