Nanostructure Formation and Passivation of Large-Area Black Silicon for Solar Cell Applications

Nanoscale textured silicon and its passivation are explored by simple low‐cost metal‐assisted chemical etching and thermal oxidation, and large‐area black silicon was fabricated both on single‐crystalline Si and multicrystalline Si for solar cell applications. When the Si surface was etched by HF/AgNO3 solution for 4 or 5 min, nanopores formed in the Si surface, 50–100 nm in diameter and 200–300 nm deep. The nanoscale textured silicon surface turns into an effective medium with a gradually varying refractive index, which leads to the low reflectivity and black appearance of the samples. Mean reflectance was reduced to as low as 2% for crystalline Si and 4% for multicrystalline Si from 300 to 1000 nm, with no antireflective (AR) coating. A black‐etched multicrystalline‐Si of 156 mm × 156 mm was used to fabricate a primary solar cell with no surface passivation or AR coating. Its conversion efficiency (η) was 11.5%. The cell conversion efficiency was increased greatly by using surface passivation process, which proved very useful in suppressing excess carrier recombination on the nanostructured surface. Finally, a black m‐Si cell with efficiency of 15.8% was achieved by using SiO2 and SiNX bilayer passivation structure, indicating that passivation plays a key role in large‐scale manufacture of black silicon solar cells. Nanoscale textured silicon is explored by simple low‐cost metal‐assisted chemical etching; large‐area black silicon is fabricated both on single‐crystalline Si and multicrystalline Si for solar cell applications. The Ag nanoparticles tend to form at the kinks, steps, and other defects first, and these initial nanoparticles become bigger than the others and catalyze the oxidation of Si more effectively.