Micro/nano structure size effect on superhydrophobicity and anti reflection of single crystalline Si solar cells

Si surface modification is of great significance for a variety of applications, such as hydrophobic treatment, surface passivation of photovoltaic devices, and microelectronic devices. In this study, a facile way of forming superhydrophobic surfaces is reported that uses KOH etching and Au assisted HF/H2O2 etching of silicon wafers. The Au layer was deposited onto a pyramidal silicon wafer via e-beam evaporation. By controlling the evaporation and etching times, the effect of micro/nano scale roughness was manipulated and superhydrophobic surfaces with reduced hysteresis were generated. Light reflection on the as prepared black surfaces was measured to assess the efficiency for low cost solar cell applications. The two scale roughness surface showed a much reduced reflectance compared to that of pyramid textured silicon surfaces which are commonly employed in high efficiency solar cells. The effect of micro/nano size on light reflection properties was also studied. This approach offers a new way both to theoretically study the surface roughness effect and to investigate engineering applications of self-cleaning surfaces in solar cells. Such surface could also be applied in plastic packaging of IC device.