Organic conjugated polymers are a new class of semiconducting materials and have demonstrated significant applications in large-area and flexible thin-film optoelectronic devices based on two unique features: convenient material processability and facile property-tuning. As compared with inorganic semiconductors, polymers have an important distinct feature: coexistence of differently spin-configured singlet and triplet states. As a result, a net spin-polarization due to external spin-polarized charge transfer or spin injection should have a significant impact on the electronic processes associated with the singlet and triplet states, and may open a new direction to control the optoelectronic properties of organic conjugated polymer devices based on magnetic interactions.
Objective: This project seeks to investigate a critically important issue: effects of spinpolarized charge transfer on singlet and triplet exciton formation and singlet-triplet intersystem crossing in organic semiconducting polymers. With one-year support, this SGER will develop a solid interdisciplinary research program that will comprehensively study the effects of spin injection and transfer on (i) exciton dissociation of photogenerated polarized excitons (photovoltaics), (ii) spin-polarized charge trapping and releasing (nonvolatile memory), (iii) spin polarized electron-hole recombination (electroluminescence), and (iv) spin dependent exciton-exciton coherence (lasing actions) in organic n-conjugated materials.
Intellectual merit: This project necessitates a truly interdisciplinary research effort, including: i) synthesis and processing of conjugated polymers and ferro-magnetic nanomaterials, ii) device fabrication, iii) advanced characterization of optoelectronic and magnetic properties. The approach is to first understand spin-polarized charge transfer from magnetic nano-materials to conjugated polymer chains. Secondly, the effects of spin transfer on polymer optoelectronic properties will be systematically investigated. Finally, mechanism of magnetic dependent exciton formation and intersystem crossing will be elucidated. The proposed studies are expected to increase our understanding on how magnetic properties affect the optoelectronic processes in organic materials, and thus will lead to magnetically enhanced functionalities and performance of organic devices.
Broad impact: The project will develop a guideline of how to mutually control magnetic and semiconducting properties, and hence will significantly contribute to the development of multifunctional semiconducting magnetic organic materials for large-area and flexible optoelectronic and spintronic applications. The research consists of crossfield investigations that will provide multi-disciplinary training in optics, electronics, and magnetics to the involved graduate and undergraduate students by exposing them to problems related to the development of organic optoelectronic and spintronic materials and devices. To further enhance its educational impact, this SGER will develop new course work for Polymer Physics (MSE 543) and Optoelectronic Processes in Polymeric Materials and Devices (MSE 674) at the University of Tennessee.
