SCANNING CURRENT SPECTROSCOPY: A CONDUCTING PROBE ATOMIC FORCE MICROSCOPY TECHNIQUE FOR EXPLORING THE PHYSICAL AND ELECTRONIC PROPERTIES OF METAL OXIDE/ORGANIC INTERFACES

Persistent Link:
http://hdl.handle.net/10150/195049
Title:
SCANNING CURRENT SPECTROSCOPY: A CONDUCTING PROBE ATOMIC FORCE MICROSCOPY TECHNIQUE FOR EXPLORING THE PHYSICAL AND ELECTRONIC PROPERTIES OF METAL OXIDE/ORGANIC INTERFACES
Author:
Veneman, Peter Alexander
Issue Date:
2009
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Organic photovoltaics (OPVs) offer the prospect of inexpensive processing compared with conventional crystalline semiconductor cells. These cells are still lower in efficiency than their inorganic counterparts, in part because a detailed understanding of the role that interfaces play in these devices is lacking. The electronic properties of the surface of the common transparent electrode Indium:Tin Oxide (ITO) have been studied both on a macroscopic and nanoscopic scale, and the interface between ITO and organic materials has been studied on a macroscopic scale as well. Little work has been done on the nanoscopic properties of the ITO/organic interface. This dissertation introduces a new conducting-probe atomic force microscope (CP-AFM) technique, Scanning Current Spectroscopy (SCS), for probing the nanoscopic lateral variation in the electronic properties of this interface, and demonstrates its utility by examining the ITO/copperphthalocyanine (CuPc) interface. SCS demonstrates large lateral variations in the hole collection efficiency at that interface on a nanometer length scale, and that the distribution of these variations is affected by ITO pretreatment. Measurements on OPVs demonstrate that the performance of these devices is dependant on the nanoscopic lateral variation in surface properties that SCS measures, and that in the case of the ITO/CuPcinterface SCS explains the observed device behavior better than techniques that yield macroscopic average electronic properties, such as photoelectron spectroscopy. Additionally, this dissertation discusses advances made in the design of an integrated optical refractive index sensor. The sensor uses organic light-emitting diodes (OLEDs) and OPVs as integrated light-sources and detectors on top of a slab waveguide substrate. The platform offers potentially high sensitivities to refractive index changes (and the selective binding of chemical and biological analytes), and is amenable to largescale integration for on-chip multiplexed detection. The refractive index response has been demonstrated previously, but the performance was limited by electrical noise and OLED drift. The use of different absorbing species in the OPV, integration of multiplesensors on a single substrate, addition of a reference channel to monitor OLED drift andthe use of lock-in amplification for signal processing allow the sensor to detect changesof 10-4 refractive index units.
Type:
text; Electronic Dissertation
Keywords:
AFM; heterogeneous electrode; ITO; organic photovoltaic; scanning current spectroscopy
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Armstrong, Neal R.
Committee Chair:
Armstrong, Neal R.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleSCANNING CURRENT SPECTROSCOPY: A CONDUCTING PROBE ATOMIC FORCE MICROSCOPY TECHNIQUE FOR EXPLORING THE PHYSICAL AND ELECTRONIC PROPERTIES OF METAL OXIDE/ORGANIC INTERFACESen_US
dc.creatorVeneman, Peter Alexanderen_US
dc.contributor.authorVeneman, Peter Alexanderen_US
dc.date.issued2009en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractOrganic photovoltaics (OPVs) offer the prospect of inexpensive processing compared with conventional crystalline semiconductor cells. These cells are still lower in efficiency than their inorganic counterparts, in part because a detailed understanding of the role that interfaces play in these devices is lacking. The electronic properties of the surface of the common transparent electrode Indium:Tin Oxide (ITO) have been studied both on a macroscopic and nanoscopic scale, and the interface between ITO and organic materials has been studied on a macroscopic scale as well. Little work has been done on the nanoscopic properties of the ITO/organic interface. This dissertation introduces a new conducting-probe atomic force microscope (CP-AFM) technique, Scanning Current Spectroscopy (SCS), for probing the nanoscopic lateral variation in the electronic properties of this interface, and demonstrates its utility by examining the ITO/copperphthalocyanine (CuPc) interface. SCS demonstrates large lateral variations in the hole collection efficiency at that interface on a nanometer length scale, and that the distribution of these variations is affected by ITO pretreatment. Measurements on OPVs demonstrate that the performance of these devices is dependant on the nanoscopic lateral variation in surface properties that SCS measures, and that in the case of the ITO/CuPcinterface SCS explains the observed device behavior better than techniques that yield macroscopic average electronic properties, such as photoelectron spectroscopy. Additionally, this dissertation discusses advances made in the design of an integrated optical refractive index sensor. The sensor uses organic light-emitting diodes (OLEDs) and OPVs as integrated light-sources and detectors on top of a slab waveguide substrate. The platform offers potentially high sensitivities to refractive index changes (and the selective binding of chemical and biological analytes), and is amenable to largescale integration for on-chip multiplexed detection. The refractive index response has been demonstrated previously, but the performance was limited by electrical noise and OLED drift. The use of different absorbing species in the OPV, integration of multiplesensors on a single substrate, addition of a reference channel to monitor OLED drift andthe use of lock-in amplification for signal processing allow the sensor to detect changesof 10-4 refractive index units.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectAFMen_US
dc.subjectheterogeneous electrodeen_US
dc.subjectITOen_US
dc.subjectorganic photovoltaicen_US
dc.subjectscanning current spectroscopyen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorArmstrong, Neal R.en_US
dc.contributor.chairArmstrong, Neal R.en_US
dc.contributor.committeememberSaavedra, S. Scotten_US
dc.contributor.committeememberPemberton, Jeanne E.en_US
dc.contributor.committeememberMcGrath, Dominic V.en_US
dc.identifier.proquest10781en_US
dc.identifier.oclc659753624en_US
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