A study of the surface morphology of silicon : Effect of parasitic emitter etching on the rear side performance of silicon solar cells

Abstract

Silicon solar cells with dielectric passivation layers need enhanced rear surface treatment. In this work we will introduce a novel masking and etching procedure whereby the parasitic emitter etching, the increase of the rear reflectance and finally the improvement of the rear surface passivation will be merged in only one step. Using adapted acidic etching solutions we can show a higher etch rate at pyramid peaks of textured rear sides. This selectivity of the etch rate will allow significant change of the surface morphology without increased material loss. This fact makes the application of thin solar cells more attractive. This novel method is transferred not only to screenprinted solar cell concepts with full area Al-BSF, but also to solar cells with dielectrically passivated rear sides. The rounding effect of the rear side texture with minimized abrasion leads to high rear side reflectance and increased surface passivation of dielectrically passivated solar cells. A significant gain of 0.5 mA/cm² of solar cells with an adapted rear side morphology confirms the mentioned advantages of this novel etching procedure with masking.