title: Mechanisms of enhanced optical absorption for ultrathin silicon solar microcells with an integrated nanostructured backside reflector.
abstract: This paper investigates mechanisms of enhanced light absorption exhibited by ultrathin Si solar microcells integrated with a periodically nanostructured, semitransparent metallic reflector. This backside reflector comprises periodic nanoscale relief features formed by soft-imprint lithography with a thin (~35 nm) coating of Au. The work shows that microcells placed in direct contact above the nanostructured reflector's surface creates Fabry-Pérot cavities, which traps impinging light inside the Si slab via the excitation of cavity modes. Experimental measurements show that the short-circuit current and efficiency values for devices incorporating this thin, semitransparent backside reflector outperform similar Si microcells integrated with a planar thick (~300 nm) opaque mirror by ~10-15% because of enhanced absorption. Computational modeling that is supported by experimental measurements reveal that the dominant methods of enhancement stem from a complex interplay between backside diffraction/scattering and Fabry-Pérot resonances. These same data demonstrate that plasmonic interactions contribute minimally to the optical enhancements seen.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Corcoran
authors.forename: Somi
authors.initials: S
authors.lastname: Kang
authors.forename: Lanfang
authors.initials: L
authors.lastname: Li
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Guo
authors.forename: Debashis
authors.initials: D
authors.lastname: Chanda
authors.forename: Ralph G
authors.initials: RG
authors.lastname: Nuzzo