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, 〈1 1 1〉 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.