Design of Chemical Additives with Polyphenyl Sulfonate Derivatives for Surface Texturing on Monocrystalline Silicon

High-efficiency, green, stable and economical texturing molecules and the relative additive composition are considered as one of the key tasks to obtain a light trapping structure with an ultra-low reflectivity and to improve the photoelectric conversion efficiency of monocrystalline silicon solar cell. In this work, polyphenyl skeleton was used to strength the interfacial interaction between silicon crystalline face and texturing molecules, while sulfonic, hydroxy and alkoxy groups regulate the texturing sites. Sodium 6-naphthalene disulfonate, sodium 2-hydroxy-7-naphthalene sulfonate, sodium dodecyl diphenyl ether sulfonate and sodium lignosulfonate were selected to investigate their texturing effects. The results show that larger molecular size, dispersed polyphenyl skeleton, flexible molecular structure, abundant hydroxyl and alkoxy groups for polyphenyl sulfonate derivatives facilitate the generation of a continuous, uniform and dense pyramid structure on monocrystalline silicon surface. Based on the comparative experimental results at different reaction parameters (i.e., texturing molecule structure, concentration, reaction time and temperature), sodium lignosulfonate was selected as an effective texturing reagent. In a low mass fraction range of 0.0006%–0.06%, the single use of sodium lignosulfonate can lead to a low reflectivity of 15.84%–26.94%. A low-concentration and high-stability additive composition with 0.015% (in mass fraction, the same below) sodium lignosulfonate, 1.1% sodium dodecylbenzene sulfonate and 2.0% 2-hydroxy-β-cyclodextrin can be obtained via systematic orthogonal experiments in the presence of a surfactant and an antifoaming agent. A desired texturing surface featured with a uniform, dense pyramid structure sized at 1.7–1.9 μm and an average reflectivity of 9.89% occurs at 75–85 ℃ for 200–400 s when adding this additive into 0.65% NaOH aqueous solution as a corrosive agent. This work can provide a reference for the development of green, efficient and practical additives for texturing on monocrystalline silicon based on polyphenyl sulfonate derivatives as a texturing agent.