Tuning the Current of Organic Semiconductors by Magnetic Fields

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

Technical. This project combines a theoretical and experimental approach to address resistance, photoconductivity, light emission, photovoltaic, and field effect transistor response of organic- and polymer-based organic materials at room temperature and low magnetic fields (<100 Oe), with the objective of establishing a broadly applicable model that describes and predicts mag-netic field effects at low fields. Experiments will be guided by predictions of competing mecha-nisms for low field behavior, magnetoresistance due to interconversion of singlets and triplets (MIST mechanism) and magnetic field control of bipolaron transport. Experiments will be car-ried out to explore the roles of chemical composition, processing, and microstructure to clarify and understand mechanisms or develop new models for magnetotransport in several classes of organic-based semiconductors including small molecules, oligomers, conjugated polymers, and non-conjugated polymers. Organic based LEDs with different spin-orbit and hyperfine interac-tion strengths will be fabricated and studied as a function of magnetic field and electric field. In particular, oligomers where there are long lived excitons and carbon-based material such as C60, graphene, where the hyperfine constant is anticipated to be negligible are of special interest. In situ EPR study of organic- and polymer-based LEDs will also be used to study spin transfer. Non-Technical. The project addresses fundamental research issues in a topical area of elec-tronic/photonic materials science having technological relevance. Basic understanding gained is expected to lead to improved device performance, and to allow design of other important com-ponents for future plastics electronics. Magnetic field effects in organic- and polymer-based semiconductors represents an emerging field in nanoscience with impact in areas such as or-ganic- and polymer based photovoltaics, light emitters, and spintronics. The project integrates re-search and education providing students with hands-on laboratory experience and training while conducting forefront research.