title: Metal-Insulator-Semiconductor Nanowire Network Solar Cells.
abstract: Metal-insulator-semiconductor (MIS) junctions provide the charge separating properties of Schottky junctions while circumventing the direct and detrimental contact of the metal with the semiconductor. A passivating and tunnel dielectric is used as a separation layer to reduce carrier recombination and remove Fermi level pinning. When applied to solar cells, these junctions result in two main advantages over traditional p-n-junction solar cells: a highly simplified fabrication process and excellent passivation properties and hence high open-circuit voltages. However, one major drawback of metal-insulator-semiconductor solar cells is that a continuous metal layer is needed to form a junction at the surface of the silicon, which decreases the optical transmittance and hence short-circuit current density. The decrease of transmittance with increasing metal coverage, however, can be overcome by nanoscale structures. Nanowire networks exhibit precisely the properties that are required for MIS solar cells: closely spaced and conductive metal wires to induce an inversion layer for homogeneous charge carrier extraction and simultaneously a high optical transparency. We experimentally demonstrate the nanowire MIS concept by using it to make silicon solar cells with a measured energy conversion efficiency of 7% (∼11% after correction), an effective open-circuit voltage (Voc) of 560 mV and estimated short-circuit current density (Jsc) of 33 mA/cm(2). Furthermore, we show that the metal nanowire network can serve additionally as an etch mask to pattern inverted nanopyramids, decreasing the reflectivity substantially from 36% to ∼4%. Our extensive analysis points out a path toward nanowire based MIS solar cells that exhibit both high Voc and Jsc values.
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF , Science Park 104, 1098 XG, Amsterdam, The Netherlands.
authors.forename: Sebastian Z
authors.initials: SZ
authors.lastname: Oener
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF , Science Park 104, 1098 XG, Amsterdam, The Netherlands.
authors.forename: Jorik
authors.initials: J
authors.lastname: van de Groep
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology , 5600MB Eindhoven, The Netherlands.
authors.forename: Bart
authors.initials: B
authors.lastname: Macco
authors.affiliation: ECN Solar Energy, Westerduinweg 3, 1755ZG Petten, The Netherlands.
authors.forename: Paula C P
authors.initials: PC
authors.lastname: Bronsveld
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology , 5600MB Eindhoven, The Netherlands.
authors.forename: W M M
authors.initials: WM
authors.lastname: Kessels
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF , Science Park 104, 1098 XG, Amsterdam, The Netherlands.
authors.forename: Albert
authors.initials: A
authors.lastname: Polman
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF , Science Park 104, 1098 XG, Amsterdam, The Netherlands.
authors.forename: Erik C
authors.initials: EC
authors.lastname: Garnett
keywords: Metal−insulator−semiconductor; nanopyramids; nanowire networks; solar cells