title: Engineering Schottky contacts in open-air fabricated heterojunction solar cells to enable high performance and ohmic charge transport.
abstract: The efficiencies of open-air processed Cu2O/Zn(1-x)Mg(x)O heterojunction solar cells are doubled by reducing the effect of the Schottky barrier between Zn(1-x)Mg(x)O and the indium tin oxide (ITO) top contact. By depositing Zn(1-x)Mg(x)O with a long band-tail, charge flows through the Zn(1-x)Mg(x)O/ITO Schottky barrier without rectification by hopping between the sub-bandgap states. High current densities are obtained by controlling the Zn(1-x)Mg(x)O thickness to ensure that the Schottky barrier is spatially removed from the p-n junction, allowing the full built-in potential to form, in addition to taking advantage of the increased electrical conductivity of the Zn(1-x)Mg(x)O films with increasing thickness. This work therefore shows that the Zn(1-x)Mg(x)O window layer sub-bandgap state density and thickness are critical parameters that can be engineered to minimize the effect of Schottky barriers on device performance. More generally, these findings show how to improve the performance of other photovoltaic system reliant on transparent top contacts, e.g., CZTS and CIGS.
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
authors.forename: Robert L Z
authors.initials: RL
authors.lastname: Hoye
authors.forename: Shane
authors.initials: S
authors.lastname: Heffernan
authors.forename: Yulia
authors.initials: Y
authors.lastname: Ievskaya
authors.forename: Aditya
authors.initials: A
authors.lastname: Sadhanala
authors.forename: Andrew
authors.initials: A
authors.lastname: Flewitt
authors.forename: Richard H
authors.initials: RH
authors.lastname: Friend
authors.forename: Judith L
authors.initials: JL
authors.lastname: MacManus-Driscoll
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Musselman
keywords: Cu2O solar cells; Schottky barrier; electrochemical deposition; spatial atmospheric atomic layer deposition; zinc magnesium oxide