Effects of Etching Solution Concentration on Silicon Surface Reflectivity as a Solar Cell Surface Modifier

Abstract

The surface structure of single-crystal silicon is known to be one of the best ways to reduce reflection, increase light trapping ability, and increase light absorption. The hierarchical surface structure plays an important role in reducing the reflectivity of single-crystalline silicon surfaces. Through this research, the size and density of the pyramids formed on the silicone surface and their relationship to changes in the concentration of the etching solution during silicone processing were studied and evaluated. The pyramids etched on the silicon surface formed photo-traps that increased the efficiency of light absorption. The effects of hydroxylamine (NH₂OH) on a 20 wt% KOH and 20wt% NaOH solution were investigated. The concentration of NH₂OH variedfrom 6 to 18wt% while the etching temperature was kept at 70 °C and the etching time was at 40 minutes. In this work, optimal etch concentrations were determined, and it was found that a 20 wt% KOH + 18wt% NH₂OH solution was superior tothe 20 wt% KOH solution.The normal incidence percent reflectivitywas 6.5%, at 640 nm wavelength, for Si {100} surfaces etched in a 20wt% NaOH + 18wt% NH₂OH solution. This normal incidence percent reflectivity valuewas slightly higher than that achieved by the 20wt% pure NaOH solutionwhere a percent reflectivity of 6.0% was measured at the same wavelength. Moreover, the addition of NH₂OH leads to a noticeable increase in the size of the etched pyramid structures.