Doctor of Philosophy

dissertationThe portmanteau spintronics defines the technological utilization of the spin degree of freedom as information carrier in electronic devices. In order to implement spintronics technologies, various microscopic processes in condensed matter can be used including spin injection, spin transport, spin manipulation, and spin measurement techniques, the latter of which can be accomplished by various means, including the utilization of spin-dependent electronic transitions for electron spin readout. This dissertation is focused on the experimental study of two of these mechanisms in a variety of organic semiconductor materials, namely (a), spin-dependent electronic transitions, whose physical nature is observed with electrically and optically detected magnetic resonance spectroscopies (EDMR and ODMR, respectively) and (b), spin transport of pure spin currents, the flow of magnetic polarization in absence of net charge currents, which is observed using pulsed inverse spin-Hall effect (p-ISHE) spectroscopy. In particular, the following results are presented: (i) It is shown that the dynamics of electron spin states in polymer-based organic light emitting diodes (OLEDs) is governed by hyperfine interactions with hydrogen nuclei (protons). Hyperfine coupling strengths are obtained from current measurements during and after the coherent excitation of coupled electron spin states. (ii) Transient current and electroluminescence responses of OLEDs after pulsed magnetic resonance excitation of charge carrier spin states by simultaneous detection of both, the changes of electrical current and light emission correlations between the dynamics of EDMR and ODMR signals can be obtained. This allows the verification of spin-dependent polaron pair recombination as the origin of the observed EDMR and ODMR signals. (iii) p-ISHE spectroscopy is used to study spin diffusion length and spin-orbit coupling (SOC). This technique, based on ferromagnetic resonance (FMR) driven spin current generation with strong electromagnetic pulses, is particularly well suited for materials with inherently weak SOC. The pulsed technique also allows to minimize measurement artifacts caused by heating and other electromagnetic effects. (iv) The development of a pulsed Rabi nutation of paramagnetic spin-probes that allows for a precise control of the p-ISHE driving field strength and homogeneity