Improvement of the Surface Structure for the Surface Passivation of Black Silicon

Black silicon (B-Si) has been extensively applied in the photovoltaic field for its prominent light-trapping feature, but its large surface area also brings plenty of structural defects. In this article, a postetching treatment by using acid mixed solution consisted of HNO3/HF/H2O was adopted to balance the tradeoff between optical gain and electrical losses on metal-catalyzed chemical etching B-Si surfaces. We studied the effect of etching time on the reflectance and surface passivation of B-Si on polished and pyramid textured silicon substrates. The result shows that compared with the NaOH postetching applied in the industrial product line, the acid mixed solution could improve the surface passivation and low reflectance within the etching time of 3 min. Moreover, on the base of industrial anisotropic NaOH etch procedure, within etching time of 2 min, the reflectance and S-eff decreased by 2.93% and 36.5 cm/s respectively. This fast and combined postetching treatment is a potential industrial method to obtain low reflectance and surface recombination loss.