FRG: Spin Response in Organic Semiconductors with Tuned Hyperfine Interaction

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Technical AbstractThe goals of the proposed research are the study of electron spin injection, manipulation, transport and detection in organic two-terminal devices such as spin-valves, diodes, and light emitting diodes; as well as the inter-relation between the injected electron spins and nuclear spins in these devices. In particular the injected spin aligned carrier dynamics, the dynamic of the resulting nuclear polarization and its influence on the electronic spin response, as well as the electroluminescence response in spin-organic light emitting diodes will be thoroughly investigated. The novel experiments will be conducted in spintronics devices based on organic semiconductors such as polymers, small molecules, and fullerenes, in which some of the building block atoms would be replaced by less abundant isotopes having different hyperfine strength. This includes replacing protonated hydrogen (1H) by deuterated hydrogen (2H); and/or 12C by the 13C isotope. The studies will contribute to the understanding of the physical processes that govern the spin response in organic spin devices, and have the potential to revolutionize their performance. This project will support the education of two PhD students in these advanced technologies, which is excellent training for many scientific careers from academia to our most advanced technology industries. These experiments are expected to be of general interest to the scientific community and provide new spintronics techniques especially for pursing new information bearing media.Non-Technical AbstractRecently the spin degree of freedom of the electron that is associated with its internal magnetic moment has been investigated as an information carrying medium, in addition to the electron charge. It has been predicted that the electrical current would be augmented by spin current in future devices. The organic semiconductor has started to play an important role in the electronics and displays industries, as well as in solar energy harvesting. Organic spintronics is a new concept, where the spin is manipulated in organic semiconductor devices. This proposal deals with spin manipulation in organic electronic devices. Spins will be injected, controlled and detected in various organic materials of which molecular building blocks contain different isotopes such as deuterium that replaces hydrogen, and 13C that replaces the more abundant 12C in the organics. It is postulated that the electron spin coherence is lost because of the nuclei in the organic that also carry spins; this occurs due to the electron-spin/nuclear-spin interaction also known as hyperfine interaction. Although very tiny, this interaction plays a destructive role in spintronics because there are so many nuclei in the material. In this proposal the role of isotope exchange will be investigated in a number of organic spin devices, with the goal to improve the spin coherence time. A cadre of undergraduate students as well as 2 graduate students will participate in the projects, gaining training and hands-on experience in frontier scientific research. Through the research experience, the students will be well equipped to pursue a graduate education or start a career in the semiconductor/nanotechnology industries.