Reactive sputtered Ta2O5 antireflection coatings

Abstract Ta2O5 antireflection coatings were prepared by reactive sputtering from a tantalum target in a magnetron system. The optical constants of the films were determined from reflectance and transmittance spectra in the 0.25-2.5 μ wavelength interval. The refractive index was close to 2.0 in the visible region, resulting in optimum impedance matching for silicon solar cells. The sputtred Ta2O5 films showed an absorption coefficient smaller than about 103 cm–1 for photon energies below 4 eV. Finally sputtered Ta2O5 antireflection coatings were tested on silicon solar cells and were found to increase the efficiency of the cells from 9.5% to 12.9%.