Texturing of monocrystalline silicon wafers by HF-HCl-H2O2 mixtures: Generation of random inverted pyramids and simulation of light trapping in PERC solar cells

Abstract Solutions containing hydrofluoric acid (HF), hydrochloric acid (HCl), and hydrogen peroxide (H 2 O 2 ) were investigated as novel acidic, NO x -free etching mixtures for texturing of monocrystalline silicon wafers. High etch rates of up to 13.3 nm s −1 were observed at room temperature, which are comparable to the etch rates of KOH-IPA solutions. The silicon surface was investigated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), indicating pyramidal textures for diamond wire and SiC-slurry sawn as well as saw-damage etched (polished) wafers. Non-stirred baths generate random pyramidal structures while constantly stirred solutions generate novel random inverted pyramidal surface structures. The light trapping efficiency of wafers etched by the HF-HCl-H 2 O 2 solutions was compared by UV/vis-reflectivity measurements to KOH/ i -propanol specimens indicating lower reflectivities for the HF-HCl-H 2 O 2 -treated samples. Using the ‘wafer ray tracer’ (pvlighthouse.com) the light absorption properties of monomodal and random inverted pyramid structures were simulated and compared to well-known random and monomodal textures for PERC solar cells, clearly indicating the best performance for random inverted pyramids. Besides, simulation of a PERC solar cell on a roof top at our university was performed, indicating improved performance, especially for random inverted pyramid textures.