| The rapid growth of the world’s population, the increasing depletion of energyand the pollution of environment were the three major problems facing humanity,since the20thcentury. Thus people have a great demand for energy, especially in newenergy development which is famous for its cleaning. Solar energy attracts theattention of many researchers for its extensive, cleaning and richness. Solar cell issuch a device which converts solar energy into electrical energy; it works by using thephotoelectric effect of the p-n junction. For an ideal solar cell, its conversionefficiency is a characteristic is depending on the characteristic of the material, thestructure of the cell and the doping concentration of the p-n junction. But for a realsolar cell, apart from the above factors, the leakage current of p-n junction and theseries resistance cause by electrode due and material charactering should beconsidered. The effect of series resistance is an important factor in the low efficiencyof an actual cell. A suitable choice of electrode material and the electrode structure isnot only possible to improve the conversion efficiency of cell, and also to reduce thecost of the cell.In this paper, the nickel-copper electrode is prepared by using electrochemicalmethod as the front finger of crystalline silicon solar cells to replace the conventionalsilver electrode. SEM and XRD were used to characterize the performance of thenickel middle layer and nickel-copper electrode layer. The study showed that a goodnickel middle layer was prepared by using electrochemical method. Nickel silicidewas formed after sintered at500℃, which would enhance the adhesion betweennickel layer and silicon substrate. Copper layer was not closely arranged at the surfaceof the nickel layer, due to the uneven of the nickel layer. After sintered, a smallamount of the copper would fall off. Meanwhile, copper nickel compound was formedafter sintered.Rare earth can improve the performance of the nickel deposited layer as anadditive. In this paper, La, Ce and Er were used to prepared nickel middle layer asadditive. The performance of the layer was compared with the nickel layer preparedwithout adding any rare earth. The results showed that the performance of nickelmiddle layer was improvement by adding rare earth. When adding Ce as additive, the adhesion between nickel middle layer and silicon substrate was improvement. And theporosity and sheet resistance was decrease. Thus, comparatively speaking, Ce wasmore suitable as an additive to prepare front finger of solar cell.Copper electrode layer was prepared after nickel middle layer deposited. Theinfluence of Ce was investigated by compared with the nickel-copper layer withoutadding Ce. SEM and XRD analysis showed that the nickel/copper system was loosenand cannot form a dense copper layer when without adding RE as the additive. Aftersinter, there is copper silicide generated, which indicated that nickel middle layercannot hinder copper electrode layer into silicon substrate. Adding cerium as theadditive to preparing nickel/copper electrode layer is denser; no copper silicide isformed after sintering, that the relatively dense nickel intermediate layer can be agood barrier to the diffusion of the copper electrode into the substrate. After sintering,the rare earth cerium prepared Ni/Cu electrode layer and the sheet resistance of rareearth cerium prepared nickel/copper layer were6.83×10-3/□and1.28×10-2/□.The cerium additive, the sheet resistance is reduced to half. |
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