Ultralow reflectivity surfaces by formation of nanocrystalline Si layer for crystalline Si solar cells

•Ultralow reflectivity surface of a nanocrystalline Si layer/Si structure.•Surface passivation of a nanocrystalline Si layer using phosphosilicate glass.•A high photocurrent density of 39.2 mA/cm2 without anti-reflection coating.•A high conversion efficiency of 18.2%.

We have developed a simple method to form a nanocrystalline Si layer, which simply involves contact of Pt catalysts with Si wafers immersed in an H2O2 plus HF solution. The reflectivity becomes less than 3% after the formation of the nanocrystalline Si layer of ~150 nm thickness. High quality pn-junction can be produced on the nanocrystalline Si/crystalline Si structure. With surface passivation using the deposition method, p-type single crystalline Si-based solar cells with the nanocrystalline Si layer generate a high photocurrent density of 39.2 mA/cm2 under the standard test condition (STD) even without anti-reflection coating and the conversion efficiency of 18.2% is achieved. The passivation method using deposition of phosphosilicate glass on the nanocrystalline Si layer followed by annealing in forming gas improves the quantum efficiency in the short-wavelength region ranging between 300 and 600 nm.