title: Role of Defects and Surface States in the Carrier Transport and Nonlinearity of the Diode Characteristics in PbS/ZnO Quantum Dot Solar Cells.
abstract: The roles of bulk surface states and interfacial defects are probed experimentally using a combination of current-voltage, capacitance-voltage, and impedance measurements. The critical importance of the quality of both the film and interfaces is evident in current-voltage measurements where shunting and interface states result in large dark currents and the subsequent loss of Jsc. These properties are shown to be critically related to the nature and role of the PbS QD interface with the (nominally) ohmic gold contact. Specifically, the nonideality of this interface results in the formation of an electric field and therefore a Schottky barrier that opposes the transport of carriers across the conventional ZnO-PbS CQD system. Nonidealities in the structure and absorber layer are also reflected in nonmonotonic behavior and dispersion in C-V measurements with trapping processes on the CQD surfaces, and the ZnO/PbS and PbS/Au interfaces also affecting the carrier dynamics, which is reflected in the response time of these systems under different biases.
authors.affiliation: Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma , 440 W. Brooks Street, Norman, Oklahoma 73019, United States.
authors.forename: Y
authors.identifier: http://orcid.org/0000-0003-1499-060X
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma , 440 W. Brooks Street, Norman, Oklahoma 73019, United States.
authors.forename: M D C
authors.initials: MDC
authors.lastname: Whitaker
authors.affiliation: Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma , 440 W. Brooks Street, Norman, Oklahoma 73019, United States.
authors.forename: R
authors.initials: R
authors.lastname: Makkia
authors.affiliation: Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma , 440 W. Brooks Street, Norman, Oklahoma 73019, United States.
authors.forename: S
authors.initials: S
authors.lastname: Cocklin
authors.affiliation: Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma , 440 W. Brooks Street, Norman, Oklahoma 73019, United States.
authors.forename: V R
authors.initials: VR
authors.lastname: Whiteside
authors.affiliation: Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma , 440 W. Brooks Street, Norman, Oklahoma 73019, United States.
authors.forename: L A
authors.initials: LA
authors.lastname: Bumm
authors.affiliation: Department of Chemistry and Biochemistry, University of Tulsa , 800 South Tucker Drive, Tulsa, Oklahoma 74104, United States.
authors.forename: E
authors.initials: E
authors.lastname: Adcock-Smith
authors.affiliation: Department of Chemistry and Biochemistry, University of Tulsa , 800 South Tucker Drive, Tulsa, Oklahoma 74104, United States.
authors.forename: K P
authors.initials: KP
authors.lastname: Roberts
authors.affiliation: Department of Physics and Engineering Physics, University of Tulsa , 800 South Tucker Drive, Tulsa, Oklahoma 74104, United States.
authors.forename: P
authors.initials: P
authors.lastname: Hari
authors.affiliation: Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma , 440 W. Brooks Street, Norman, Oklahoma 73019, United States.
authors.forename: I R
authors.initials: IR
authors.lastname: Sellers
keywords: PbS quantum dots; Schottky diodes; impedance spectroscopy; mid-gap states; tunneling