A Robust Metal-Assisted Etching Process for Ag-Catalyzed Texturing of Silicon

Silicon structures with excellent light-trapping performance have been developed using a silver-catalyzed metal-assisted etching (MAE) process. The MAE process can be well controlled through variation in solution composition and exposure times, even when the process is conducted on obscured, polished, (111) surfaces. Light trapping was calculated to be >90% of Lambertian for the best performing sample, with solar weighted average reflectance (R_w) of 13% when λ = 400-1000 nm. This represents an 18% reflectance reduction compared with a planar sample and 13% improvement compared with a sample with conventional isotexture. This was improved further by encapsulation of the sample, reducing R_{w(400-1000 nm)} for the MAE-textured sample to 2%. The structures were well passivated using atomic layer deposition and demonstrate surface recombination velocities (S_eff) of ≈30 cm·s^-1 at injection levels of Δn = 1015 cm^-3.