Laser interference-driven fabrication of regular inverted-pyramid texture on mono-crystalline Si

We show that inverted-pyramid (IP) textures can be fabricated on mono-crystalline Si wafer by laser interference combined with alkali etching. When exposed to three interfering nanosecond-laser beams at 532 nm, the surface was periodically melted in accordance with the interference pattern, generating concave holes. Subsequent etching with a KOH solution revealed IP structures as a result of the anisotropic etching. It was found that not only the etching condition but also the in-plane orientation relationship of interfering beams is an important factor to fabricate low-reflectance, uniform IP textures. An average reflectance less than 20% was obtained over the spectral range of 400 nm to 1 μm. This mask-free process may be effectively utilized for the production of low-cost, high-efficiency crystalline Si solar cells.