Enhanced light absorption and minority carrier lifetime for pn+ multicrystalline silicon by treatment with HF/H2O2-based solutions

A novel method was proposed to form porous silicon (PS) antireflection layers and thin SiO2 films at the same time by HF/H2O2 treatment of acid-textured pn(+) multicrystalline silicon. Porous silicon structures formed inside the cavities and the porosity became large with an increase of the treated time resulting in a dramatical decrease of reflectance. The reflectance decreased to less than 5% within the wavelength range of 420-970 nm after 5 min HF/H2O2 treatment. Furthermore, the minority-carrier lifetime showed an increase of about 42% for a short treated time because of the formation of a thin silicon oxide layer resulting the reduction of dangling silicon bonds in the interface between PS/Si.