Experimental optimization of an anisotropic etching process for random texturization of silicon solar cells

A multifactor experimental investigation of silicon surface texturing was conducted using aqueous potassium-hydroxide (KOH) solutions with isopropyl alcohol (IPA) added as a complexing agent. Czochralski, magnetic-Czochralski, and float-zone silicon wafers of different resistivities with both polished and lapped surfaces were included in the experiment. Process variables considered were solution temperature, time in solution, degree of mechanical mixing, KOH concentration, and IPA concentration. Using hemispherical reflectance as the primary gauge of success, process variables that resulted in an effective surface texture with reflectance less than 12% prior to antireflection coating were identified. Of particular interest was a low-temperature (70°C) process with less than 2% concentration of both KOH and IPA and wide process variable tolerances