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Abstract: We report polarity-switchable polymer solar cells that use poly [(9,9-bis((6′-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene)-alt-(9,9-bis(2-(2-(2-methoxy-ethoxy)ethoxy)ethyl)-9-fluorene))dibromide polyelectrolyte (WPF-6-oxy-F). By introducing WPF-6-oxy-F as a polarity-controlling layer, we selectively achieved polarity switching in the device operation. When we deposited the WPF-6-oxy-F film on the top of an active polymer layer, the device operated conventionally; holes moved to the transparent indium tin oxide (ITO) electrode. However, the device showed switched polarity when we changed the position of insertion of the WPF-6-oxy-F film to the top of the transparent ITO electrode. Then, the electrons moved to the transparent ITO electrode, leading to an inverted device. [Copyright &y& Elsevier]

Abstract: Space charge is a key insulation problem of HVDC equipment. In this paper, the influence of voltage polarity and electrode material were studied by the pulse electroacoustic (PEA) method. It had been found that the type of space charge accumulating at the interface was the same with the voltage polarity. With different electrode materials, the space charge injection was consequently different, but not evident. The interface made the drift velocity slower in two-layer samples. It suggested that the interface had a significant impact on space charge distribution and the contact state was complex, so a modified Maxwell–Wagner model was proposed. [Copyright &y& Elsevier]

Abstract: In this study, surface Dielectric Barrier Discharge (DBD) actuators powered by nanosecond pulsed high voltage are investigated. The goal is to experimentally characterize the surface DBD actuators in terms of electrical and geometrical parameters. The actuators are made of two conducting electrodes separated by a thin dielectric (Kapton films) and arranged asymmetrically. The active electrode is connected to a pulsed high voltage power supply (voltage up to ±10 kV, rise and fall times of 50 ns and pulse width of 250 ns) and the second electrode is grounded. The experimental results show that the energy per pulse (normalized by the length of the active electrode) is smaller when one increases the inter-electrode spacing between 1 and 3 mm, the thickness of the dielectric barrier between 120 and 360 μm or the length of the electrodes between 10 and 50 cm, for both applied voltage polarities. Optical characterization of the plasma layer for different electrode gaps has been investigated by using an ICCD camera. Results indicate that the plasma produced by positive and negative rising voltage propagates in a streamer-like regime with numerous and well-distributed channels, for any electrode gap distance. However, the positive and negative falling voltage produces similar discharges only for large electrode gaps. In this case, the plasma layer starts from a corona spot in contact with the active electrode and expands in the direction of the grounded electrode in a plume shape. [Copyright &y& Elsevier]

Abstract: Recently bipolar resistive switching of transition metal oxides is investigated to be used in next-generation non-volatile memory technologies. Switchable resistance states are based on reduction and oxidation (redox) reactions within the oxides. In the first part of this study resistive switching in Fe-doped SrTiO3 thin films is discussed. Careful conductive tip AFM analysis revealed that after the electroforming and top electrode removal a very complex switching behavior emerges. Locally separated filamentary as well as area dependent switching with different switching polarity with respect to the bias polarity of the SET and RESET processes were observed in the same sample. In the second part of the paper nanocrossbar devices are proposed as a vehicle to ease the comparison of promising materials using identical device geometry. The potential scaling behavior of resistively switching memory elements is addressed by the preparation of nominally 100 × 100 nm2 crosspoint structures using two different transition metal oxides, namely NiO and TiO2. [Copyright &y& Elsevier]