Broadband omnidirectional antireflection coatings optimized by genetic algorithm

Abstract

An optimized graded-refractive-index (GRIN) antireflection. (AR) coating with broadband and omnidirectional characteristics-as desired for solar cell applications-designed by a genetic algorithm is presented. The optimized three-layer GRIN AR coating consists of a dense TiO2 and two nanoporous SiO2 layers fabricated using oblique-angle deposition. The normal incidence reflectance of the three-layer GRIN AR coating averaged between 400 and 700 nm is 3.9%, which is 37% lower than that of a conventional single-layer Si3N4 coating. Furthermore, measured reflection over the 410-740 run range and wide incident angles 40 degrees-80 degrees is reduced by 73% in comparison with the single-layer Si3N4 coating, clearly showing enhanced omnidirectionality and broadband characteristics of the optimized three-layer GRIN AR coating. (C) 2009 Optical Society of America