Black silicon film with modulated macropores for thin-silicon photovoltaics

Abstract

We present a kind of “one-step strategy” to produce black silicon film where the antireflection/light-trapping structures and the silicon film itself are fabricated simultaneously and directly from a silicon wafer. We first demonstrate that the macroporous black silicon has better light harvesting capability and longer lifetime of minority carriers than silicon nanowires of the same thickness, leading to higher efficiency when assembled into liquid junction photoelectrochemical solar cells. A free-standing macroporous black silicon film is further detached from the substrate and the measured absorption in the near infrared region is close to the theoretical limit without the help of back reflectors. FDTD simulations reveal that the modulation on the micrometer scale can scatter strongly and thus enhance the absorption of the originally weakly absorbed light.