title: Flexible thin-film black gold membranes with ultrabroadband plasmonic nanofocusing for efficient solar vapour generation.
abstract: Solar steam generation has been achieved by surface plasmon heating with metallic nanoshells or nanoparticles, which have inherently narrow absorption bandwidth. For efficient light-to-heat conversion from a wider solar spectrum, we employ adiabatic plasmonic nanofocusing to attain both polarization-independent ultrabroadband light absorption and high plasmon dissipation loss. Here we demonstrate large area, flexible thin-film black gold membranes, which have multiscale structures of varying metallic nanoscale gaps (0-200 nm) as well as microscale funnel structures. The adiabatic nanofocusing of self-aggregated metallic nanowire bundle arrays produces average absorption of 91% at 400-2,500 nm and the microscale funnel structures lead to average reflection of 7% at 2.5-17 μm. This membrane allows heat localization within the few micrometre-thick layer and continuous water provision through micropores. We efficiently generate water vapour with solar thermal conversion efficiency up to 57% at 20 kW m(-2). This new structure has a variety of applications in solar energy harvesting, thermoplasmonics and related technologies.
authors.affiliation: School of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
authors.forename: Kyuyoung
authors.initials: K
authors.lastname: Bae
authors.affiliation: School of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
authors.forename: Gumin
authors.initials: G
authors.lastname: Kang
authors.affiliation: Department of Electrical, Computer &Energy Engineering and Materials Science &Engineering Program, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: Suehyun K
authors.initials: SK
authors.lastname: Cho
authors.affiliation: Department of Electrical, Computer &Energy Engineering and Materials Science &Engineering Program, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: Wounjhang
authors.initials: W
authors.lastname: Park
authors.affiliation: School of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
authors.forename: Kyoungsik
authors.initials: K
authors.lastname: Kim
authors.affiliation: Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Willie J
authors.identifier: http://orcid.org/0000-0001-7734-8847
authors.initials: WJ
authors.lastname: Padilla