Recent advances in organic spin response include long polaron spin-coherence times measured by optically detected magnetic resonance (ODMR), substantive room-temperature magnetoelectroluminescence and magnetoconductance obtained in organic light-emitting diodes (OLEDs) and spin-polarized carrier injection from ferromagnetic electrodes in organic spin valves (OSVs). Although the hyperfine interaction (HFI) has been foreseen to have an important role in organic spin response, no clear experimental evidence has been reported so far. Using the chemical versatility advantage of the organics, we studied and compared spin responses in films, OLED and OSV devices based on pi-conjugated polymers made of protonated, H-, and deuterated, D-hydrogen having a weaker HFI strength. We demonstrate that the HFI does indeed have a crucial role in all three spin responses. OLED films based on the D-polymers show substantially narrower magneto-electroluminescence and ODMR responses, and as a result of the longer spin diffusion obtained, OSV devices based on D-polymers show a substantially larger magnetoresistance.

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Periodically organized magnetic cobalt frameworks have been fabricated by a combination of colloidal self-assembly and electrochemical deposition. The ordered cobalt frameworks have a closed-packed face-centered-cubic inverse opal structure and are fabricated as micrometer-thick films. The size and density of the cobalt crystallites that compose the cobalt frameworks can be modified by a thermal annealing step following the electrodeposition. Comparison of the magnetic properties (studied by magneto-optical Kerr effect (MOKE) spectroscopy) of as-deposited and annealed samples reveals strong impact of the annealing process. Fitting the obtained MOKE response to a modified Langevin model reveals optimum values of coercivity, pinning site density, and inter-domain coupling for samples that are thermally annealed at 440 °C.

We measured the picoseconds (ps) transient photomodulation (PM) dynamics of photoexcitations in blends of regio-regular poly(3-hexyl-thiophene) [RR-P3HT] (donors-D) and indene-C60 bisadduct (fullerene derivative) [ICBA] (acceptor-A) that phase-separate into D- and A-nano-domains, in a broad spectral range from 0.25 to 2.5 eV; in comparison with steady state PM spectra. We correlate our measurements with organic photovoltaic solar cell performance made from the same D and A materials. In D-A blends of RR-P3HT/ICBA with (1.2:1) weight ratio having solar cell power conversion efficiency of ∼5.1%, we found that although the intrachain excitons in the polymer nano-domains decay within ∼10 ps, no charge polarons are generated on their expense up to ∼1 ns. Instead, there is a built-up of charge-transfer (CT) excitons at the D-A domain interfaces that occurs with the same kinetics as the exciton decay. The CT excitons dissociate into separate polarons in the D- and A-nano-domains at a much later time (≫1 ns). This “two-step” charge photogeneration process is typical in organic bulk heterojunction cells. Our results emphasize the important role of the CT state in generating free charge polarons in organic solar cells.

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To determine a general correlation between structure and dynamic magnetic properties of porous materials, the frequencies of magnetic spin waves are studied by Brillouin light scattering from nickel inverse opals and backed up by micromagnetic simulations. Within the observed unit cell size regime between 400 and 800 nm, discrete thickness standing modes are found to change with unit cell size. By applying pair correlation functions of the inverse opal solid phase normal to the applied field to an equation for perpendicular standing modes, the directional and unit cell size‐dependent spectral intensities above the surface mode region can be traced. Thus, an accessible general approach for the prediction of standing spin waves in porous materials is obtained.