The results of the optimization of antireflection films of TiO 2 nanotubes on GaAs solar cells, non-encapsulated and encapsulated, are presented. The ARC forms a bilayer of porous TiO 2 over a dense bottom. The films were prepared on Si and GaAs substrates via a versatile electrochemical anodization process which produces films with good optical performance. The thicknesses and porosity of the ARC were optimized numerically with a method based on maximizing the short circuit current. Using experimental indices, the minimum R w was 1.81% for the non-encapsulated case. For the encapsulated case, the lowest R w was 2.34%, where the porosity of the top layer was adjusted in addition to the thicknesses. In simulations of a GaAs solar cell, the addition of the optimized ARC resulted in a J sc increase of 43.6% for the non-encapsulated case, and 36.7% for the encapsulated case. • Nanostructured TiO 2 films prepared via anodic oxidation method for use as ARC. • Numerical optimization of ARCs with emphasis on space applications. • Analysis of a GaAs solar cell with and without coverglass with good anti-reflection properties. • Device simulation including electrical parameters and EQE of the solar cell with optimized ARC.