Faculty Profile
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Oliver MontiAssociate ProfessorEmail: monti@email.arizona.edu Building: OC 216 Phone: 520-626-1177 | Honors
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Education and Appointments
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Research Interests
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Research Summary | |
Interfacial Structure and Dynamics in Organic Photovoltaic Cells
Research in my group is focused on obtaining a detailed understanding of interfacial processes in organic electronic devices such as organic photovoltaic cells. Their function is largely controlled by interfacial processes such as exciton dissociation, polaron formation, geminate recombination and carrier transport. Interfaces are intrinsically complex environments, with typically high defect densities and complex structure. This is compounded by the bulk heterojunction architecture, currently the most efficient architecture for organic solar cells, with structure on the micron to nanometer length-scale. Such heterogeneity makes it difficult to extract the underlying physics of charge generation and transport. As a consequence, the development of solar cells with significantly higher power conversion efficiencies presents a major challenge.  Our research seeks to elucidate the chemistry and physics of carriers in organic semiconductors at interfaces on the short length- and time-scales present in organic photovoltaic cells. We develop and use novel forms of optical microscopy in combination with ultrafast photoelectron spectroscopy to study the electronic structure and dynamics of organic semiconductors under highly controlled conditions. Check out our research group page for the latest news!Using this experimental approach, we are pursuing research in several complementary directions: 1. Interface formation and charge transport at organic/metal and organic/organic boundaries for organic solar cells, organic light emitting diodes and thin film transistors. We use two-photon photoemission spectroscopy to study charge generation and transport at highly controlled interfaces. This approach lets us investigate both occupied (HOMO) and unoccupied (LUMO, higher lying excited states and sometimes transport levels) states at organic semiconductor interfaces, giving insight e.g. to the role of the interface on molecular energy levels and intermolecular interactions. Recent work has focused on the role of short- and long-range electrostatic fields at the interface, showing dramatic effects on interfacial electronic structure. 2. Exciton dissociation at efficient heterojunctions occurs on fs to ps timescales. We attempt to obtain an understanding of the dynamics of this process at a controlled bulk heterojunction by following the exciton survival with chemically selective ultrafast pump-probe spectroscopy. This allows us to obtain a much more precise understanding of the charge transfer mechanisms at play in organic semiconductor devices and will help develop a more efficient bulk heterojunction with fast carrier generation without compromising efficient carrier transport. 3. In order to obtain a detailed picture of the exciton dissociation process, we reduce the complex bulk heterojunction typically used in organic solar cells to a model system, where charge transfer occurs from a single molecule to a single crystalline wide bandgap semiconductor under highly defined conditions. Ensemble measurements often obscure some of the most intriguing aspects of such small-scale systems. This requires us to look at individual molecules in order to capture the complete picture and allows us to investigate effects of surface state densities, defect densities, distance etc. on exciton dissociation efficiencies. These experimental results are also accessible to high level ab inito calculations. Visit also the UA Chemical Physics Program! | |
Selected Publications | |
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