Design and fabrication of multi-layer antireflection coating for III-V solar cell

ZnS and ZnS–MgF2 composite films were prepared on soda-lime glass substrates and MgF2 films on GaAs by rf magnetron sputtering to investigate multi-layer antireflection (AR) coatings. Optical constants of these films were determined by envelope method and spectroscopic ellipsometry. In particular, ZnS–MgF2 composite films were fabricated by co-sputtering of ZnS and MgF2 target to obtain intermediate refractive index material for a middle layer in the triple-layer AR coating and these films exhibited the desired intermediate refractive index. Based on the extracted optical constants, single-, double- and triple-layer AR coatings on GaAs substrates were designed and fabricated by rf magnetron sputtering. Low reflectance could be obtained from single-layer AR coating only at a specific wavelength and could be obtained from multi-layer AR coating at wide wavelength regime. Additionally, incident angle dependence of the reflectance of the multi-layer AR coatings was also investigated and showed different behavior according to a number of layers.