title: Multiple-exciton generation in lead selenide nanorod solar cells with external quantum efficiencies exceeding 120.
abstract: Multiple-exciton generation-a process in which multiple charge-carrier pairs are generated from a single optical excitation-is a promising way to improve the photocurrent in photovoltaic devices and offers the potential to break the Shockley-Queisser limit. One-dimensional nanostructures, for example nanorods, have been shown spectroscopically to display increased multiple exciton generation efficiencies compared with their zero-dimensional analogues. Here we present solar cells fabricated from PbSe nanorods of three different bandgaps. All three devices showed external quantum efficiencies exceeding 100% and we report a maximum external quantum efficiency of 122% for cells consisting of the smallest bandgap nanorods. We estimate internal quantum efficiencies to exceed 150% at relatively low energies compared with other multiple exciton generation systems, and this demonstrates the potential for substantial improvements in device performance due to multiple exciton generation.
authors.affiliation: Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Nathaniel J L K
authors.initials: NJ
authors.lastname: Davis
authors.affiliation: Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Marcus L
authors.initials: ML
authors.lastname: Böhm
authors.affiliation: Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Maxim
authors.identifier: http://orcid.org/0000-0001-9390-3791
authors.initials: M
authors.lastname: Tabachnyk
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: Florencia
authors.initials: F
authors.lastname: Wisnivesky-Rocca-Rivarola
authors.affiliation: Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Tom C
authors.identifier: http://orcid.org/0000-0003-2729-6430
authors.initials: TC
authors.lastname: Jellicoe
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: Caterina
authors.initials: C
authors.lastname: Ducati
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.
authors.forename: Bruno
authors.initials: B
authors.lastname: Ehrler
authors.affiliation: Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Neil C
authors.initials: NC
authors.lastname: Greenham