Antireflection nanostructure was formed by simple wet chemical etching using catalysis of silver (Ag) nanoparticle. Single nano-sized Ag particle dispersion solution was coated onto Si(1 0 0) substrate with polished surface. Then, the samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. The surface of 9-min-etched Si substrate appeared black, and the reflectivity was reduced to below 5% throughout the entire spectrum from 200 to 1000 nm owing to the formed nanostructure. The absorption was significantly increased after the formation of antireflection structure with 9 min etching, and the conversion efficiency of solar cell with antireflection structure increased from 8.25 to 10.0% owing to the increase of short-circuit current. (C) 2009 Elsevier B.V. All rights reserved.