title: Nano-cones for broadband light coupling to high index substrates.
abstract: The moth-eye structure has been proposed several times as an antireflective coating to replace the standard optical thin films. Here, we experimentally demonstrate the feasibility of a dielectric moth-eye structure as an antireflective coating for high-index substrates, like GaAs. The fabricated photonic crystal has Si3N4cones in a square lattice, sitting on top of a TiO2index matching layer. This structure attains 1.4% of reflectance power losses in the operation spectral range of GaAs solar cells (440-870 nm), a 12.5% relative reduction of reflection power losses in comparison with a standard bilayer. The work presented here considers a fabrication process based on laser interference lithography and dry etching, which are compatible with solar cell devices. The experimental results are consistent with scattering matrix simulations of the fabricated structures. In a broader spectral range (400-1800 nm), the simulation estimates that the nanostructure also significantly outperforms the standard bilayer coating (3.1% vs. 4.5% reflection losses), a result of interest for multijunction tandem solar cells.
authors.affiliation: IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), E-28760 Tres Cantos, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Buencuerpo
authors.affiliation: IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), E-28760 Tres Cantos, Madrid, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Torné
authors.affiliation: IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), E-28760 Tres Cantos, Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Álvaro
authors.affiliation: IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), E-28760 Tres Cantos, Madrid, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Llorens
authors.affiliation: IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), E-28760 Tres Cantos, Madrid, Spain.
authors.forename: M L
authors.initials: ML
authors.lastname: Dotor
authors.affiliation: IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), E-28760 Tres Cantos, Madrid, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Ripalda