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As hydrogen gas increasingly becomes critical as a carbon-free energy carrier, the demand for robust hydrogen sensors for leak detection and concentration monitor will continue to rise. However, to...

The optical and magnetoplasmonic properties of Ag/Co and Ag/Co/Ag multilayer nanohole arrays have been investigated. By including a top- and bottom-Ag plasmonic layer onto a Co ferromagnetic perfor...

A simple and versatile touchspinning method is demonstrated for the fabrication of core-sheath nanofibrous piezoelectric yarns with a single filament electroconductive core. The polyvinylidene fluo...

The use of hydrogen as a clean and renewable alternative to fossil fuels requires a suite of flammability mitigating technologies, particularly robust sensors for hydrogen leak detection and concentration monitoring. To this end, we have developed a class of lightweight optical hydrogen sensors based on a metasurface of Pd nano-patchy particle arrays, which fulfills the increasing requirements of a safe hydrogen fuel sensing system with no risk of sparking. The structure of the optical sensor is readily nano-engineered to yield extraordinarily rapid response to hydrogen gas (, Detecting hydrogen is important for development of renewable energy sources. Here, the authors present lightweight optical hydrogen sensors based on a metasurface of PdCo nano-patchy particle arrays, which achieve sensitive hydrogen detection in less than 1 s, and without risk of sparking.

To accelerate the reduction in tuberculosis (TB) incidence, it is necessary to optimize the use of innovative tools and approaches available within a local context. This study evaluated the use of an existing network of community health workers (CHW) for active case finding, in combination with mobile chest X-ray (CXR) screening events and the expansion of Xpert MTB/RIF testing eligibility, in order to reach people with TB who had been missed by the current system. A controlled intervention study was conducted from January 2018 to March 2019 in five intervention and four control districts of two low to medium TB burden cities in Viet Nam. CHWs screened and referred eligible persons for CXR to TB care facilities or mobile screening events in the community. The initial diagnostic test was Xpert MTB/RIF for persons with parenchymal abnormalities suggestive of TB on CXR or otherwise on smear microscopy. We analyzed the TB care cascade by calculating the yield and number needed to screen (NNS), estimated the impact on TB notifications and conducted a pre-/postintervention comparison of TB notification rates using controlled, interrupted time series (ITS) analyses. We screened 30,336 individuals in both cities to detect and treat 243 individuals with TB, 88.9% of whom completed treatment successfully. All forms of TB notifications rose by +18.3% (95% CI: +15.8%, +20.8%). The ITS detected a significant postintervention step-increase in the intervention area for all-form TB notification rates (IRR(β6) = 1.221 (95% CI: 1.011, 1.475); p = 0.038). The combined use of CHWs for active case findings and mobile CXR screening expanded the access to and uptake of Xpert MTB/RIF testing and resulted in a significant increase in TB notifications. This model could serve as a blueprint for expansion throughout Vietnam. Moreover, the results demonstrate the need to optimize the use of the best available tools and approaches in order to end TB.

We studied spin dynamics of charge carriers in the superlattice-like Ruddlesden-Popper hybrid lead iodide perovskite semiconductors, 2D (BA)2(MA)Pb2I7 (with MA = CH3NH3, and BA = CH3(CH2)3NH3), and 3D MAPbI3 using the magnetic field effect (MFE) on conductivity and electroluminescence in their light emitting diodes (LEDs) at cryogenic temperatures. The semiconductors with distinct structural/bulk inversion symmetry breaking, when combined with colossal intrinsic spin–orbit coupling (SOC), theoretically give rise to giant Rashba-type SOC. We found that the magneto-conductance (MC) magnitude increases monotonically with the emission intensity and saturates at ≈0.05% and 0.11% for the MAPbI3 and (BA)2(MA)Pb2I7, respectively. The magneto-electroluminescence (MEL) response with similar line shapes as the MC response has a significantly larger magnitude, and essentially stays constant at ≈0.22% and ≈0.20% for MAPbI3 and (BA)2(MA)Pb2I7, respectively. The sign and magnitude of the MC and MEL responses can be quantitatively explained in the framework of the Δg-based excitonic model using rate equations. Remarkably, the width of the MEL response in those materials linearly increases with increasing the applied electric field, where the Rashba coefficient in (BA)2(MA)Pb2I7 is estimated to be about 7 times larger than that in MAPbI3. Our studies might have significant impact on future development of electrically-controlled spin logic devices via Rashba-like effects.

The magnetoplasmonic properties of Ag-Co composite nanohole arrays are investigated. It is observed that both plasmonic and magnetic properties of the Ag-Co composite nanohole arrays strongly depend on the composition ratio of Ag and Co. The enhanced optical transmission due to plasmonic resonance decreases with the increase of the Co component while the Faraday rotation effect increases monotonically. The magnetization dynamics of a composite thin film is also modified by the composition as well as the introduction of hole arrays. The Ag-Co composite nanohole arrays with the Co content of 30% show high plasmonic--magneto-optics performances compared with that of Ti-Co composite nanohole array, and annealing of the Ag-Co composites in vacuum can further improve this property. All experimental results are confirmed by the finite-difference time-domain calculations. Such a magnetoplasmonic composite material can act as a class of materials for magnetoplasmonic devices or metamaterial applications.

Spintronics (also known as spin-based electronics) is an emerging technology that exploits the intrinsic spin transport of electrons other than their fundamental electronic charge. Organic semiconductors (OSCs) are composed of light elements that have weak spin-orbit interaction; consequently, they have long spin relaxation times, which makes them viable candidates for spin-transport materials in spintronics devices. Two types of organic spintronics devices have been extensively studied in the past few years: organic spin valves (OSVs) and organic light-emitting diodes (OLEDs), in which both conductivity and electroluminescence (EL) have been strongly modulated by an external magnetic field. In addition, optically detected magnetic resonance (ODMR) is an excellent complementary tool for investigating the electron-spin dynamics in OSCs. In this chapter, we describe the role of hyperfine interaction (HFI) in the spin response of films and devices based on conjugated polymers (CPs) made of protonated, H-hydrogen, deuterated, D-hydrogen, and 13C-rich chains. We experimentally prove that the HFI indeed plays a crucial role in all three spin responses. First, OLEDs based on the D-polymer show substantial narrower magneto-conductance (MC) and magneto-electroluminescence (MEL) responses. And the ultra-small MC and MEL responses at magnetic fields of few Gauss are also strongly isotope-dependent. Second, due to the longer obtained spin diffusion, OSV devices based on D-polymer show substantially larger magneto-resistance (MR) than devices based on H-polymers or C13-rich polymers. Films based on the D-polymer show considerably narrower polaron spin-half resonance than for H-polymers and C13-rich polymers. We also describe the time-resolved magneto-photoinduced absorption in π-conjugated copolymers in the time domain of picosecond to millisecond. Finally, our theoretical model describes these time-resolved magneto-photoinduced absorption results.

In the preceding review paper, Paper I [Journal of Science: Advanced Materials and Devices 1 (2016) 128–140], we showed the major experimental and theoretical studies on the first organic spintronic subject, namely organic magnetoresistance (OMAR) in organic light emitting diodes (OLEDs). The topic has recently been of renewed interest as a result of a demonstration of the magneto-conductance (MC) that exceeds 1000% at room temperature using a certain type of organic compounds and device operating condition. In this report, we will review two additional organic spintronic devices, namely organic spin valves (OSVs) where only spin polarized holes exist to cause magnetoresistance (MR), and spin organic light emitting diodes (spin-OLEDs) where both spin polarized holes and electrons are injected into the organic emissive layer to form a magneto-electroluminescence (MEL) hysteretic loop. First, we outline the major advances in OSV studies for understanding the underlying physics of the spin transport mechanism in organic semiconductors (OSCs) and the spin injection/detection at the organic/ferromagnet interface (spinterface). We also highlight some of outstanding challenges in this promising research field. Second, the first successful demonstration of spin-OLEDs is reviewed. We also discuss challenges to achieve the high performance devices. Finally, we suggest an outlook on the future of organic spintronics by using organic single crystals and aligned polymers for the spin transport layer, and a self-assembled monolayer to achieve more controllability for the spinterface.

Gas sensors are critical for facilitating the safety and integrity of systems used in the hydrogen energy and storage systems. It is challenging for any sensing technology to meet all the performance requirements for emerging applications, such as dynamic measuring range, response time, and sensitivity. Here, we propose an optical hydrogen gas sensor platform based on Pd bilayer plasmonic nano-lattices (BPNL), which is comprised of two parallel, subwavelength-separated hexagonal arrays of Pd nano-patchy particles and nano-holes. Optical transmission studies of the BPNL structure and its isolated sub-structures of nano-patches (NPs) and nano-hole arrays (NHs) upon hydrogen sorption show distinct optical isotherms with different spectral changes and response times in the visible-to-near-infrared region. Experiments and finite-difference time-domain (FDTD) calculations show that the strong electromagnetic coupling between localized and propagating plasmonic modes of the NPs and NHs, respectively, leads to the unique optical properties of the BPNL and their subsequent change upon hydrogen sorption. Notably, the BPNL structure possesses an extended optical response range and enhanced sensitivity for hydrogen detection. Additionally, the optical response time of the BPNL structure is an order of magnitude faster than that of the isolated array sensors in the low hydrogen pressure range. Finally, we demonstrate that the sensing characteristics of such a BPNL platform can be further improved by tuning its structural parameters.

Toroidal dipoles, unlike electric and magnetic dipoles, are formed due to currents flowing on the surface of a torus along it’s meridians. We investigate the toroidal dipole response in a graphene based infinite 2D array of terahertz (THz) metamaterial (MM) and report the active tuning of the toroidal resonances. Each metamolecule in our proposed MM configuration consists of two joint split ring resonators (SRRs) made up of graphene material with two gaps in each resonator. We examine actively tunable response of the toroidal excitations with respect to a change in the Fermi energy of graphene material. The toroidal effect is elaborated using surface current and magnetic field profiles at the resonance frequency of the metamolecule structure. The modulation of the metamaterial’s toroidal response and effect on Q factor is further examined by changing the relaxation time of graphene. The excitation of toroidal resonances at terahertz frequencies and their dynamic control could be significant in designing efficient tunable modulators, filters and sensors.

We review the fi rst 10 years of research on organic spin-valve devices in the fi eld of organic spintronics. The device fi gure of merit, magnetoresistance, is governed by the hyperfi ne interaction of the organic interlayer and the ability of the ferromagnetic electrodes to inject spin-polarized carriers. By choosing a deuterated π -conjugated polymer with a relatively long spin diffusion length as the organic interlayer and using a thin LiF buffer layer to raise the Fermi level of the cathode, a bipolar spin-valve device could be obtained in which the electroluminescence emission intensity is controlled by an external magnetic fi eld. We show that the underlying physics of this spin-organic light-emitting diode is very different from that of a unipolar organic spin valve because of the magnetic properties of the spin-polarized bipolar space charge limited current in the device.

The magneto-plasmonic properties of Ag-Co composite nano-triangle arrays are investigated. Both plasmonic and magnetic properties of the samples are found to strongly depend on the composition ratio of Ag and Co. Composite nano-triangle arrays exhibit strong plasmonic properties and low magneto-optics (MO) effect with high composition of Ag, and vice versa. The enhanced magneto-optic effect is also observed to be coincident with the localized surface plasmon resonance (LSPR) properties, i.e. the maximum Faraday effect occurs at the LSPR wavelength, which is due to locally high E-field. The composite triangle arrays with the 60% Co content show high plasmonic-MO performances characterized by magneto-optics-plasmonic correlation factor. All experimental results are confirmed by finite-difference time domain calculations.

Utilizing the magneto-resistance response of organic light emitting diodes (OLEDs) at ultra-small magnetic field we show that both the value and direction of the local earth magnetic field ( B E ) can be accurately obtained. We further demonstrate a ‘compass response’ in the magneto-conductance and magneto-electro-luminescence of OLEDs based on three isotopes of a π-conjugated polymer. We found that both responses are dependent on the direction of a small, fixed magnetic field B 0 (≈50 μT) with respect to B E , and this effect is used to determine B E direction. We conjecture that living creatures may use the same principle for magneto-reception and navigation.

Hyperfine interaction (HFI) has been considered as a dominant spin mixing mechanism in conventional semiconducting polymers causing large magnetoconductance (MC) in organic diodes. However, the relationship between the MC width or HFI strength and the MC magnitude has not been investigated. We studied the correlation between the width and the magnitude of the MC response in organic diodes made by several conventional π-conjugated semiconducting polymers. First, by comparing the MC responses in electron- and hole-only unipolar devices made by the same polymer, we found that the electron-only device with a larger MC width always show a larger MC magnitude than that in the corresponding hole-only device. Second, we intentionally decreased and increased the charge localization or HFI strength in these unipolar devices by controlling their annealing temperature and UV irradiation, respectively. We found that the MC magnitude in these unipolar devices generally increases when the HFI strength increases but with different rates. We conclude that the width of MC or HFI strength is a crucial but not a unique factor that influences the MC magnitude. Finally, although the HFI in bipolar devices is smaller than that in the corresponding electron-only devices, the MC magnitude in bipolar devices is always larger than that in the electron-only devices suggesting that their underlying mechanisms are different.

In inorganic semiconductor spintronics the spin-diffusion length is usually limited by spin–orbit coupling. Here we examine the effect of spin–orbit coupling in organic spintronics. We consider singly charged π -conjugated polymer chains. We show that the diagonal matrix elements for spin–orbit coupling are zero. Even the off-diagonal matrix elements are zero or negligibly small unless a twisted, non-planar polymer chain is considered. We calculate these matrix elements as a function of twist angle using tight-binding wavefunctions. We show that time reversal symmetry prevents spin–orbit induced spin-precession and propose a phonon-assisted spin-flip process.

We demonstrate that multi-walled carbon nanotubes (MWCNTs) are capable of supporting surface plasmon-polaritons (SPPs) at terahertz (THz) frequencies. To achieve this, we fabricated sub-100 μm-thick freestanding and highly oriented multi-walled carbon nanotube (MWCNT) aerogel sheets. Utilizing terahertz time-domain spectroscopy, we measured the complex index of refraction of the sheets for two orthogonal nanotube orientations. We found that the MWCNT sheets exhibit highly anisotropic THz polarization behavior. Based on the extracted dielectric properties of the medium, which show that it exhibits metallic behavior in the THz spectral range, we investigated the existence and propagation of SPPs by studying the resonantly enhanced transmission through periodic MWCNT hole arrays. We found that carbon nanotubes support SPP excitations that propagate along the tubes, but highly suppress these surface waves in the direction perpendicular to the nanotubes.

We experimentally demonstrate the ability to create additional transmission resonances in a double-layer aperture array by varying the interlayer gap spacing. In the case of periodic aperture arrays, these additional resonances are sharply peaked, while for random aperture arrays the resonances are broad. Surprisingly, these additional resonances only occur when the interlayer gap spacing is greater than half the aperture spacing on a single array. Since there is no corresponding periodicity in the random arrays, these resonances occur regardless of how small the gap spacing is made. This phenomenon can be accurately modeled only if the correct frequency-dependent complex dielectric function of a metal film perforated with subwavelength apertures is used. Using THz time-domain spectroscopy, we are able to directly obtain the complex dielectric response function from the THz experimental transmission measurements. We conclude by demonstrating several passive free-space THz filters using multilayer aperture arrays. Importantly, we show that the magnitude of the lowest order resonance can be approximately maintained, while the background transmission can be significantly suppressed leading to a significant improvement in the optical filter fidelity.

We demonstrate that conically tapered cylindrical apertures can be used to efficiently concentrate broadband terahertz (THz) radiation. Keeping the aperture diameter on the input plane fixed, we show that as the diameter of the aperture on the exit plane is decreased, we obtain an increase in the magnitude of the transmitted electric field that varies inversely with the output aperture diameter. Correspondingly, the transmitted THz intensity concentration increases inversely with the square of the output aperture diameter. For the smallest aperture that we fabricated, we obtain a ~50 fold increase in the transmitted THz intensity. We expect further increases in the intensity concentration with smaller output apertures. As the output aperture diameter is decreased with a corresponding increase in the concentration factor, we directly measure an increase in the propagation time delay of a narrowband pulse through the structure. Finally, we demonstrate that further increase in the concentration factor can be achieved by engraving circular grooves around the input aperture.

We demonstrate the concentration of broadband terahertz radiation through conically tapered subwavelength apertures. Concomitantly, there is a reduction of the THz group velocity for the transmitted pulse. We describe the underlying principle behind this phenomenon.

The phenomenon of anomalous transmission through subwavelength aperture arrays in metallic films (plasmonic lattices) is thought to be mediated by surface plasmon polaritons (SPP) on the film surfaces. Using terahertz time-domain spectroscopy we systematically studied the anomalous transmission spectrum through plasmonic lattices as a function of the incidence angle, θ of the impinging beam. We observed splitting of the various transmission resonances into two resonance branches when θ deviates from normal incidence that depends on the polarization direction of the beam respect to the plane of incidence and θ. We show that the transmission resonance splitting is not related to dispersion relation of different SPP branches, but rather is associated to the interference properties of the SPP waves on the metal surface. The dependence of the split resonant frequencies vs. θ is fit with a theoretical formula that takes into account the effective dielectric function of the plasmonic lattice vs. θ, which emphasizes the important role of the Fanotype anti-resonances in the transmission spectrum. Finally, we introduced a simple way for making an efficient notch filter with high Q factor exploiting the splitting of transmission resonance under rotation.

We report on the extensive experimental characterization of a recently discovered (Francis et al., 2004) large and intriguing magnetoresistive effect in OLEDs that reaches up to 10% at room temperature for magnetic fields, B = 10mT. This magnetoresistive effect is therefore amongst the largest of any bulk material. The existence of this effect is highly surprising, since it has generally been believed that large room-temperature magnetoresistive effects can exist only in ferromagnetic devices, whereas our devices are constructed entirely from non-magnetic materials.

We report on the experimental observation of large magnetoresistance in Alq3 organic light-emitting diodes (OLEDs). Very similar magnetic field effects (MFEs) of comparable magnitude are also observed in electroluminescence and photocurrent measurements. We also report on the frequency response of the magnetoresistance effect at frequencies below 100 kHz. To the best of our knowledge, the mechanism causing these MFE is currently not known.

We report on the experimental observation of large magnetoresistance in polyfluorene organic light-emitting diodes (OLEDs). Very similar magnetic field effects (MFEs) of comparable magnitude were also observed in electroluminescence and photocurrent measurements. We provide a comprehensive overview of these three types of MFE. To the best of our knowledge, the mechanism causing these MFE is currently not known. Moreover, we show that these experiments do not allow determination whether the MFE acts on the carrier density or carrier mobility making any attempt of explaining it ambiguous. As a remedy, we performed magnetoresistance measurements in holeonly OLEDs and show that the MFE acts on the carrier mobility rather than carrier density.

We report on the experimental observation of large magnet field effect (MFE) on current and electroluminescence (EL) in polyfluorene organic light emitting diodes (OLEDs). We provide a comprehensive overview of the observed MFE. To the best of our knowledge, the mechanism causing these MFE is currently not known. Moreover, we show that these experiments do not allow determination whether the MFE acts on the carrier density or carrier mobility making any attempt of explaining it ambiguous. As a remedy, we performed magnetoresistance measurements in hole-only OLEDs and show that the MFE acts on the carrier mobility rather than carrier density.

We describe a recently discovered magnetoresistance (MR) effect in semiconducting polymer and small molecule sandwich devices. The MR effect reaches up to 10% in a magnetic field of 10mT at room temperature. This MR effect is therefore amongst the largest of any bulk material. We characterize this effect and discuss its dependence on voltage, film thickness, temperature, electrode materials and (unintentional) impurity concentration in three different organic semiconductors. We found that the MR effect is only weakly temperature dependent and does not depend on sign and direction of the applied magnetic field. To the best of our knowledge, the discovered MR effect is not adequately described by any of the mechanisms known to date.

We studied the changes in the magneto-conductance (MC) response in bipolar and unipolar organic diodes based on the π-conjugated polymer poly[2-methoxy-5-(2-ethylhexyl-oxy)-1,4-phenylene-vinylene] (MEH-PPV), upon prolonged illumination of light in the Visible–UV range. We found that the MC response in the hole-unipolar device gradually changes sign from negative to positive upon illumination, caused by the photogeneration of metastable donor-like defects in the MEH-PPV layer. This conclusion is supported by photoinduced absorption spectroscopy of pristine MEH-PPV film. In contrast, we found very little change in the MC response upon illumination of electron-unipolar devices; however, the MC response substantially increases in bipolar devices. We interpret the sign change in the MC response of hole-unipolar devices as due to illumination induced change in the spin-pairs that participate in the MC, from spin pairs of same charge to spin pairs of opposite charges.

We report studies of magnetic field effect (MFE) in polymer light-emitting electrochemical cells (PLEC) using the "super-yellow" poly-(phenylene vynilene) (SY-PPV) polymer in vertical and planar device configurations. The purpose is to discern the existing MFE mechanisms in organic light emitting diodes (OLEDs) where the current and electroluminescence are strongly modulated by a small applied magnetic field. In particular, we investigate the mutual relationship between magneto-conductance (MC) and magneto-electroluminescence (MEL) by studying the role of polaron density dissociated from polaron pairs (PP) on these magnetic responses. In general, the dissociated polaron density is determined by the PP dissociation rate and the PP density. For the planar PLEC, which possesses a small dissociation rate, we observe small and negative MC at all applied voltages regardless of the emission intensity, while MEL becomes positive when electroluminescence quantum efficiency increases. The MC has a much narrower width than the MEL, indicating that the MC and MEL do not share a common origin. However, MC reverses and has the same width as MEL when the device is exposed to a threshold laser power. For the vertical PLEC, characterized by a large dissociation rate, MC and MEL are positive and have the same width. We discuss the results using the existing MFE mechanism in OLEDs. We show that the PP model can explain the positive MEL and MC, while the negative MC can be explained by the bipolaron model. Finally, we present a possibility to complete an all-organic PLEC magnetic sensor by using an inkjet printer.

We report studies of magneto-conductance (MC) and magneto-electroluminescence (MEL) in polymer light-emitting electrochemical planar devices using “super-yellow” poly-(phenylene vinylene). We observed consistent negative MC while MEL becomes positive when electroluminescence quantum efficiency (ELQE) increases. At an optimal ELQE, the MC has a much narrower width than the MEL, indicating that the MC and MEL do not share a common origin. However, MC reverses and has the same width as MEL when exposed to a threshold laser power. We show that the e-h pair model can explain the positive MEL and MC while the negative MC can be explained by the bipolaron model.

We demonstrate that highly oriented pyrolytic graphite is a potentially useful material for plasmonic applications in the terahertz (THz) spectral range. Using THz time-domain spectroscopy, we studied the transmission properties of a ∼7.5 μm thick graphite film made via mechanical exfoliation and found that the complex dielectric constant follows the Drude model with a plasma frequency νp ∼ 34 THz. To assess the graphite plasmonic properties, we fabricated a subwavelength periodic aperture array in the graphite film and in a free-standing stainless steel film. Despite the low conductivity of graphite compared to conventional metals, the resonant transmission properties are similar.

Using terahertz (THz) transmission measurements through two-dimensional Fibonacci deterministic subwavelength hole arrays fabricated in metal foils, we find that the surface plasmon-polariton (SPP) correlation lengths for aperiodic resonances are smaller than those associated with the underlying grid. The enhanced transmission spectra associated with these arrays contain two groups of Fano-type resonances: those related to the two-dimensional Fibonacci structure and those related to the underlying hole grid array upon which the aperiodic Fibonacci array is built. For both groups the destructive interference frequencies at which transmission minima occur closely match prominent reciprocal vectors in the hole array (HA) structure-factor in reciprocal space. However the Fibonacci-related transmission resonances are much weaker than both their calculated Fourier intensity in k space and the grid-related resonances. These differences may arise from the complex, multi-fractal dispersion relations and scattering from the underlying grid arrays. We also systematically studied and compared the transmission resonance strength of Fibonacci HA and periodic HA lattices as a function of the number of holes in the array structure. We found that the Fibonacci-related resonance strengths are an order of magnitude weaker than that of the periodic HA, consistent with the smaller SPP correlation length for the aperiodic structure.

We report on the experimental characterization of a recently discovered large magnetoresistive effect in polyfluorene and in Alq3 organic light-emitting diodes. We also observe similar magnetic field effects (MFEs) of comparable magnitude in electroluminescence and photocurrent measurements. We provide a comprehensive overview of all these three types of MFE. To the best of our knowledge, the mechanism causing these MFEs is not currently known with certainty. Moreover, we show that experiments in bipolar, electroluminescent devices do not allow determination of whether the MFE acts on the carrier density or carrier mobility, making any attempt at explaining it ambiguous. As a remedy, we perform magnetoresistance measurements in hole-only polyfluorene devices and show that the MFE acts on the carrier mobility rather than carrier recombination.

Organic spintronics is an emerging and potential platform for future electronics and display due to the intriguing properties of organic semiconductors (OSCs). For the past decade, studies have focused on three types of organic spintronic phenomena: (i) magnetic field effect (MFE) in organic light emitting diodes (OLEDs), where spin mixing between singlet and triplet polaron pairs (PP) can be influenced by an external magnetic field leading to organic magnetoresistive effect (OMAR); (ii) magnetoresistance (MR) in organic spin valves (OSVs), where spin injection, transport, manipulation, and detection have been demonstrated; and (iii) magnetoelectroluminescence (MEL) bipolar OSVs or spin-OLEDs, where spin polarized electrons and holes are simultaneously injected into the OSC layer, leading to the dependence of electroluminescence intensity on relative magnetization of the electrodes. In this first of two review papers, we present major experimental results on OMAR studies and current understanding of OMAR using several spin dependent processes in organic semiconductors. During the discussion, we highlight some of the outstanding challenges in this promising research field. Finally, we provide an outlook on the future of organic spintronics.

We demonstrate that graphite is an attractive medium for plasmonics applications at THz frequencies. We accomplish this by measuring the complex dielectric properties of planar and periodically perforated graphite films using terahertz time-domain spectroscopy.