Spin Response in Organic Semiconductors with Tuned Spin-Orbit Coupling

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This project is jointly funded by the Electronic and Photonic Materials (EPM) and Condensed Matter Physics (CMP) Programs, both in the Division of Materials Research. Non-technical Description: This project is on the physical properties of newly synthesized organic polymers that contain platinum (Pt) atoms at different intervals along the polymer chain. The intrachain Pt atoms substantially enhance the coupling between the spin and the orbital angular momentum of electrons in the polymer chain. This leads to a strong red phosphorescence emission, in addition to the blue fluorescence emission known from more common polymer chains without spin-orbit coupling. The combination of both types of emission mechanisms creates white light that can serve in newly developed white organic light emitting diodes, which may replace regular bulbs in the future. Through optical, electrical and magnetic studies of these polymers, a number of fundamental scientific questions are explored that can have important ramifications on potential applications of these materials. In addition, the integration of the large arsenal of experimental techniques within the research groups of the principal investigators serves to efficiently educate graduate and undergraduate students involved in this highly interdisciplinary research project. The educational aspects of this project are in particular open to collaboration with the ACESS program at College of Science of the University of Utah, which aims to enhance the involvement of women in natural sciences.Technical Description: This research project is to study the spin-aligned carrier response as revealed by spin-pumping, spin-injection and spin-manipulation in newly synthesized pi-conjugated polymers with large spin-orbit coupling. In these polymers, Pt atoms are inserted into the organic building blocks at different intervals along the chain, which effectively tune the polymer spin-orbit coupling. The research uses a variety of novel optical, magneto-optical and electrical measurement techniques. The spin aligned carriers in Pt-polymers are polarized using the three effective techniques of spin polarization that include: spin injection by ferromagnetic electrodes, spin pumping by spin-waves in ferromagnetic substrates, and optical spin alignment by circularly polarized light absorption. The following processes are investigated: spin aligned carrier injection and transport in these polymers using the magneto-optic Kerr effect and magneto-electroluminescence; spin-current induced by spin-wave pumping in various ferromagnetic spin injectors; and photo-induced spin aligned triplet excitons. These studies 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.