Broadband Nanostructured Antireflection Coating for Enhancing GaAs Solar Cell Performance

A broadband antireflection scheme fabricated on a GaAs p-n junction solar cell (SC) is reported by implementing tapered ZnO nanoneedles on a planar tantalum pentoxide (Ta ₂ O ₅ ) coating. The abrupt refractive index transition between air and GaAs is replaced by a bottom-up surface texturing approach. The antireflection structure provides a gradual reduction of refractive index away from the SC top surface. A tapering of ZnO nanoneedle tips fused with a high refractive index Ta ₂ O ₅ layer contributed to a broadband suppression of reflectance less than 1% in the wavelength range of 380-900 nm. A power conversion efficiency enhancement of 50% is obtained by using the ZnO nanoneedle arrays on top of a planar Ta ₂ O ₅ layer. Furthermore, a 60% enhancement in the external quantum efficiency is obtained for the same wavelength range.