It is known that ferrofluid superparamagnetic nanoparticles response to external magnetic fields, often resulting in the formation of elongated clusters along the field. This has a notable impact on dielectric properties of ferrofluids. Here we report on indications of a contrary effect when the magnetic susceptibility of ferrofluids based on transformer oil is influenced by an external electric field. This effect is associated with structural changes in the ferrofluids induced by the external electric fields. Particularly, we focus on a steady state electric field effect, which gives rise to forces acting on the magnetite nanoparticles, leading to the formation of aggregates. In this condition we have measured the ferrofluid AC magnetic susceptibility in parallel and perpendicular configuration of magnetic and electric fields at room temperature. The measurements in both configurations yielded a noticeable decrease in the real susceptibility values with increasing electric field intensity. The result is believed to be caused by the reduction in the total magnetic moment of the ferrofluid. This can be a consequence of the superspin interactions in the aggregates, minimizing the aggregate's energy. Finally, we highlight the necessity of NMR and small angle scattering of polarized neutrons investigations in order to obtain exact information on the magnetic structure induced by the electric forces.

Bulk heterojunction solar cells were investigated using poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61 butyric acid methyl ester (PCBM) with a nickel oxide (NiO) anode buffer layer between the photoactive layer and an indium tin oxide (ITO) anode layer. The NiO anode buffer layer was deposited using radio frequency magnetron sputtering on an ITO electrode layer for effective hole transport and electron blocking. The NiO film is a p-type semiconductor with resistivity of 0.35 Ω cm. The power conversion efficiency was improved substantially by the NiO anode buffer layer compared to a solar cell with an anode buffer layer made from poly(3,4-ethylenedioxythiophene) (PEDOT):poly(styrene sulfonate) (PSS). The solar cell with a 10 nm thick NiO anode buffer layer had a power conversion efficiency of 4.71%. These results are explained by the improved charge transport across the interface between the active layer and ITO electrode.