Broadband antireflection and absorption enhancement by forming nano-patterned Si structures for solar cells

In this letter, we report the antireflection and light absorption enhancement by forming sub-wavelength nano-patterned Si structures via nano-sphere lithography technique. It is found that the surface reflection can be significantly suppressed in a wide spectral range (400-1000 nm) and the weighted mean reflection is less than 5%. Meanwhile, the broad band optical absorption enhancement is achieved consequently. Heterojunction solar cells are prepared by depositing ultrathin amorphous Si film on the nano-patterned Si structures, the short circuit current density increases to 37.2 mA/cm(2)and the power conversion efficiency is obviously improved compared to the reference cell on flat Si substrate.