Broadband moth-eye antireflection coatings fabricated by low-cost nanoimprinting

Subwavelength scale antireflection moth-eye structures in silicon were fabricated by a wafer-scale nanoimprint technique and demonstrated an average reflection of 1% in the spectral range from 400 to 1000 nm at normal incidence. An excellent antireflection property out to large incident angles is shown with the average reflection below 8% at 60 degrees. Pyramid array gave an almost constant average reflection of about 10% for an incident angle up to 45 degrees and concave-wall column array produced an approximately linear relation between the average reflection and the incident angles. The technique is promising for improving conversion efficiencies of silicon solar cells.