Optimization of a Nanoporous Silicon Layer for Solar Cell Application

A pyramidal structure and an n/p junction-formed wafer were used for the porous silicon (PS) layer formation. The pyramidal structure was adopted to maximize the light confinement with the PS layer. Also, in order to apply the PS layer to the solar cell directly, the n/p junction was adopted. To optimize the PS layer on this new type of surface, three kinds of solutions, ethanol, N,N-dimethylformamide, and formamide (FA), were used with hydrofluoric acid as a base of electrolyte. Various current densities were applied for PS layer formation with various anodizing durations. The reflectance and the microstructure were used as criteria for the selection of the most suitable PS layer. Consequently, an effective reflectance of 2.4% was obtained with 50 mA/cm2 and 10 s under the FA-based electrolyte condition. The result was expected to be used as an antireflection coating for solar cell applications.