title: Large Block Copolymer Self-Assembly for Fabrication of Subwavelength Nanostructures for Applications in Optics.
abstract: Nanostructured surfaces are common in nature and exhibit properties such as antireflectivity (moth eyes), self-cleaning (lotus leaf), iridescent colors (butterfly wings), and water harvesting (desert beetles). We now understand such properties and can mimic some of these natural structures in the laboratory. However, these synthetic structures are limited since they are not easily mass produced over large areas due to the limited scalability of current technologies such as UV-lithography, the high cost of infrastructure, and the difficulty in nonplanar surfaces. Here, we report a solution process based on block copolymer (BCP) self-assembly to fabricate subwavelength structures on large areas of optical and curved surfaces with feature sizes and spacings designed to efficiently scatter visible light. Si nanopillars (SiNPs) with diameters of ∼115 ± 19 nm, periodicity of 180 ± 18 nm, and aspect ratio of 2-15 show a reduction in reflectivity by a factor of 100, <0.16% between 400 and 900 nm at an angle of incidence of 30°. Significantly, the reflectivity remains below 1.75% up to incident angles of 75°. Modeling the efficiency of a SiNP PV suggests a 24.6% increase in efficiency, representing a 3.52% (absolute) or 16.7% (relative) increase in electrical energy output from the PV system compared to AR-coated device.
authors.affiliation: Advanced Materials and BioEngineering Research Centre (AMBER) & CRANN, Trinity College Dublin, The University of Dublin , Dublin 2, Ireland.|Department of Chemistry, University College Cork , Cork, T12 YN60, Ireland.
authors.forename: Parvaneh
authors.identifier: 0000-0002-5176-0478
authors.initials: P
authors.lastname: Mokarian-Tabari
authors.affiliation: Advanced Materials and BioEngineering Research Centre (AMBER) & CRANN, Trinity College Dublin, The University of Dublin , Dublin 2, Ireland.|Department of Chemistry, University College Cork , Cork, T12 YN60, Ireland.
authors.forename: Ramsankar
authors.initials: R
authors.lastname: Senthamaraikannan
authors.affiliation: Department of Chemistry, University College Cork , Cork, T12 YN60, Ireland.
authors.forename: Colm
authors.initials: C
authors.lastname: Glynn
authors.affiliation: Department of Chemistry, University College Cork , Cork, T12 YN60, Ireland.
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Collins
authors.affiliation: Advanced Materials and BioEngineering Research Centre (AMBER) & CRANN, Trinity College Dublin, The University of Dublin , Dublin 2, Ireland.
authors.forename: Cian
authors.initials: C
authors.lastname: Cummins
authors.affiliation: Elucidare Limited , Unit 9 Caxton House, Great Cambourne, CB23 6JN, U.K.
authors.forename: David
authors.initials: D
authors.lastname: Nugent
authors.affiliation: Department of Chemistry, University College Cork , Cork, T12 YN60, Ireland.|Micro-Nano Systems Centre, Tyndall National Institute , Lee Maltings, Cork, T12 R5CP, Ireland.
authors.forename: Colm
authors.identifier: 0000-0001-7429-015X
authors.initials: C
authors.lastname: O'Dwyer
authors.affiliation: Advanced Materials and BioEngineering Research Centre (AMBER) & CRANN, Trinity College Dublin, The University of Dublin , Dublin 2, Ireland.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Morris
keywords: Subwavelength nanostructures; antireflective surfaces; block copolymers; graded refractive index; omnidirectional; optics; reflectivity