Anti-reflection Coatings with Graded Refractive Index of Indium Tin Oxide for Si-based Solar Cells

Abstract

The glancing angle deposition (GLAD) technique for fabricating an antireflection (AR) structure with graded refractive index was applied to silicon substrate by using indium tin oxide (ITO) combining the sputtering method with the evaporation method. In spite of the very limited refractive index profile of ITO compared to that of the silicon substrate, the designed AR coatings at wavelengths from near infrared to near ultraviolet showed a reflectance of only 5.31% at an incident angle of 30 degrees while the transmittance of the ITO AR layer showed a sharp decrease near a wavelength of 400 nm. From these analyses, ITO multilayered AR coatings fabricated by using the GLAD method should improve the performance of an optical device after post-annealing at a low temperature of 160 degrees C. When the ITO AR coatings were applied to actual silicon solar cells, it appears that a non-grid electrode cell with ITO AR coatings is possible compared with insulator AR coatings with metal grid electrodes