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Metal additive processing in polymer: fullerene bulk heterojunction systems is recognized as a viable way for improving polymer photovoltage performance. In this study, the effect of niobium (Nb) metal nanoparticles at concentrations of 2, 4, 6, and 8 mg/mL on poly(3-hexylthiophene-2,5-diyl) (P3HT)-6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends was analyzed. The effect of Nb volume concentration on polymer crystallinity, optical properties, and surface structure of P3HT and PCBM, as well as the enhancement of the performance of P3HT:PC61BM solar cells, are investigated. Absorption of the P3HT:PC61BM mix is seen to have a high intensity and a red shift at 500 nm. The reduction in PL intensity with increasing Nb doping concentrations indicates an increase in PL quenching, suggesting that the domain size of P3HT or conjugation length increases. With a high Nb concentration, crystallinity, material composition, surface roughness, and phase separation are enhanced. Nb enhances PCBM’s solubility in P3HT and decreases the size of amorphous P3HT domains. Based on the J–V characteristics and the optoelectronic study of the thin films, the improvement results from a decreased recombination current, changes in morphology and crystallinity, and an increase in the effective exciton lifespan. At high doping concentrations of Nb nanoparticles, the development of the short-circuit current (JSC) is associated with alterations in the crystalline structure of P3HT. The highest-performing glass/ITO/PEDOT:PSS/P3HT:PCBM:Nb/MoO3/Au structures have short-circuit current densities (JSC) of 16.86 mA/cm2, open-circuit voltages (VOC) of 466 mV, fill factors (FF) of 65.73%, and power conversion efficiency (µ) of 5.16%.

Kesterite Cu2ZnSnS4 (CZTS) thin films using various 1,8-diiodooctane (DIO) polymer additive concentrations were fabricated by the electrochemical deposition method. The optical, electrical, morphological, and structural properties of the CZTS thin films synthesized using different concentrations of 5 mg/mL, 10 mg/mL, 15 mg/mL, and 20 mg/mL were investigated using different techniques. Cyclic voltammetry exhibited three cathodic peaks at −0.15 V, −0.54 V, and −0.73 V, corresponding to the reduction of Cu2+, Sn2+, Sn2+, and Zn2+ metal ions, respectively. The analysis of the X-ray diffraction (XRD) pattern indicated the formation of the pure kesterite crystal structure, and the Raman spectra showed pure CZTS with the A1 mode of vibration. Field emission scanning electron microscopy (FE-SEM) indicated that the films are well grown, with compact, crack-free, and uniform deposition and a grain size of approximately 4 µm. For sample DIO-20 mg/mL, the elemental composition of the CZTS thin film was modified to Cu:Zn:Sn: and S = 24.2:13.3:12.3:50.2, which indicates a zinc-rich and copper-poor composition. The X-ray photoelectron spectroscopy (XPS) results confirmed the existence of Cu, Sn, Zn, and S elements and revealed the element oxidation states. The electrochemical deposition synthesis increased the absorption of the CZTS film to more than 104 cm−1 with a band gap between 1.62 eV and 1.51 eV. Finally, the photovoltaic properties of glass/CZTS/CdS/n-ZnO/aluminum-doped zinc oxide (AZO)/Ag solar cells were investigated. The best-performing photovoltaic device, with a DIO concentration of 20 mg/mL, had a short-circuit current density of 16.44 mA/cm2, an open-circuit voltage of 0.465 V, and a fill factor of 64.3%, providing a conversion efficiency of 4.82%.

Modern spectroscopic techniques for the investigation of magnetization dynamics in micro and nanostructures or thin films typically use microwave antennas. They are directly fabricated on top of the sample by means of electron-beam lithography (EBL). Following this approach, every magnetic structure on the sample needs its own antenna, resulting in additional EBL steps and layer-deposition processes. Here, we demonstrate an approach for magnetization excitation that is suitable for optical and nonoptical spectroscopy techniques. By patterning the antenna on a separate flexible glass cantilever and insulating it electrically, we solve the mentioned issues. Since we use flexible transparent glass as the antenna substrate, optical spectroscopy techniques like microfocused Brillouin-light-scattering microscopy ($\ensuremath{\mu}\mathrm{BLS}$), time-resolved magneto-optical Kerr-effect measurements, or optically detected magnetic resonance measurements can be carried out at visible laser wavelengths. As the antenna is detached from the sample it can be freely positioned in all three dimensions to address only the desired magnetic structures and to achieve an effective excitation. We demonstrate the functionality of these antennas using $\ensuremath{\mu}\mathrm{BLS}$ and compare coherently and thermally excited magnon spectra to reveal an enhancement of the signal by a factor of about 400 due to the strong excitation by the antenna. Moreover, we succeed in characterizing yttrium-iron-garnet thin films with spatial resolution using optical ferromagnetic resonance experiments. We analyze the spatial excitation profile of the antenna by measuring the magnetization dynamics in two dimensions. The technique is furthermore applied to investigate injection locking of spin Hall nano-oscillators in the most favourable geometry with the highest spin-torque efficiency.

Understanding the physics of spintronic devices in the 3-nm size range can pave the way to next-generation energy-efficient information processing devices. To build a spin computer, a layer of 3-nm CoFe 2 O 4 nanoparticles was sandwiched as a central layer into the standard spin-transfer torque magnetic tunneling junction (STT-MTJ) stack. With further focused ion beam (FIB) trimming, a dual-layer junction consisting of one or more nanoparticles separating two CoFeB ferromagnetic layers was turned into a two-terminal spintronic device. The measured room-temperature electron transport through the device showed a staircase effect reminiscent of a single electron transport, which in addition depended on the relative orientations of the magnetic states of the ferromagnetic layers and the high-anisotropy ferrimagnetic nanoparticle. Besides having the staircase steps, the V-I curve indicated switching of the nanoparticles magnetization through the STT effect at currents of above 0.05 uA. The magnetoresistance (MR) curve of this device with the magnetic field applied perpendicular to the junction had an anomalous oscillatory field dependence in a relatively low field range of below 100 Oe.

This paper presents an experimental study in which 30-nm CoFe2O4–BaTiO3 core-shell magnetoelectric nanostructures (MENs) were embedded into graphite sheets to enable external control of intrinsic properties such as the intercalation process. The embedded nanoparticles were self-assembled into a honeycomb pattern with a characteristic period on the order of 200 nm, as confirmed through energy-dispersive spectroscopy (EDS) by scanning electron microscopy (SEM) as well as through atomic and magnetic force microscopy (AFM and MFM). Integration of the nanoparticles into the graphite structure was also confirmed through Fourier transform infrared (FT-IR) imaging and X-Ray diffraction (XRD) analysis. XRD measurements indicate crystallographic changes in the response to application of a 500-Oe magnetic field. M-H measurements by vibrating sample magnetometer (VSM) showed the coercivity of the nanoparticles on the order of 250 Oe.

We report the fabrication of copper zinc tin sulfide, Cu2ZnSnS4, nanoparticles by a solvothermal method. We synthesized a polymer matrix-based organic hybrid photovoltaic active layer using poly (3-hexyle thiophene) (P3HT) [6,6]: phenyl-C61-butyric-acid-methyl-ester (PCBM) and Cu2Zn SnS4 (CZTS) nanoparticles (NPs). The objective of this exploration is to verify the performance dependence of polymeric solar cells on the concentration of CZTS NPs. The active layers were doped with different concentrations of CZTS NPs (0.2, 0.4, 0.6, 0.8 mg/mL) in the P3HT: PCBM polymer. The CZTS NPs and the prepared polymer active layer were characterized by different characterization methods such as: X-ray diffraction (XRD), UV–Visible spectrophotometer, transmission electron microscopy (TEM), and Fourier Transform Infrared (FTIR), Atomic force microscopy (AFM). The hybrid photovoltaic active layer was enhanced by doping with CZTS NPs, which led to an improved homogeneous structure and incremental increases in the light absorption and electrical conductivity. X-ray diffraction (XRD) results showed that the orientation of the P3HT crystallites was affected by the blend ratio within the block polymer films. A red-shift of the FTIR results was observed as the doping concentration increased. The root-mean-square value of the samples decreased from 10.95 to 0.68 nm as the CZTS NPs concentration increased, indicating improved surface roughness. The optical properties indicated the relationship between light absorption and the morphology of the active layer. Polymer solar cells with the structure ITO/ZnO/P3HT: PCBM: CZTSNPs/Ag were fabricated. The power efficiency obtained was 3.11%, with a short-circuit current density (Jsc) of 11 mA/cm2, an open-circuit voltage (Voc) of 412 mV, and a fill factor of 68.7%.These results show the role of CZTS NPs in the development of high-efficiency P3HT:PCBM polymer solar cells.

We discuss advances in the covalent modification of the carbon allotropes, in particular graphene and carbon nanotubes. The main focus is on the organometallic chemistry that affords the possibility to electronically interconnect graphitic surfaces by means of covalent bonding. This mode of functionalization allows the formation of atomic scale interconnects that consist of bis-hexahapto-metal-bonds between benzenoid ring systems, which increases the dimensionality of the electronic structure of the materials leading to enhanced conductivity. The bis-hexahapto bond formation in single walled carbon nanotubes (SWNTs), graphite nanoplatelets and graphene, can be readily accomplished by metal vapor synthesis (e-beam evaporation), solution and photochemical routes.

In this study, polymer solar cells were synthesized by adding Sb2S3 nanocrystals (NCs) to thin blended films with polymer poly(3-hexylthiophene)(P3HT) and [6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM) as the p-type material prepared via the spin-coating method. The purpose of this study is to investigate the dependence of polymer solar cells’ performance on the concentration of Sb2S3 nanocrystals. The effect of the Sb2S3 nanocrystal concentrations (0.01, 0.02, 0.03, and 0.04 mg/mL) in the polymer’s active layer was determined using different characterization techniques. X-ray diffraction (XRD) displayed doped ratio dependences of P3HT crystallite orientations of P3HT crystallites inside a block polymer film. Introducing Sb2S3 NCs increased the light harvesting and regulated the energy levels, improving the electronic parameters. Considerable photoluminescence quenching was observed due to additional excited electron pathways through the Sb2S3 NCs. A UV–visible absorption spectra measurement showed the relationship between the optoelectronic properties and improved surface morphology, and this enhancement was detected by a red shift in the absorption spectrum. The absorber layer’s doping concentration played a definitive role in improving the device’s performance. Using a 0.04 mg/mL doping concentration, a solar cell device with a glass /ITO/PEDOT:PSS/P3HT-PCBM: Sb2S3:NC/MoO3/Ag structure achieved a maximum power conversion efficiency of 2.72%. These Sb2S3 NCs obtained by solvothermal fabrication blended with a P3HT: PCBM polymer, would pave the way for a more effective design of organic photovoltaic devices.

CVD graphene has attracted a great deal of interest from both academia and industry. The strong motivation to commercialize high quality CVD graphene films and related devices has been restricted by the lack of a cheap, efficient, clean and reliable graphene transfer process. In this article, we report a novel graphene transfer technique which provides a route to high-throughput, reliable and economical transfer of graphene without introducing large cracks and residue contamination from polymers, such as PMMA or magnetic impurities. The transferred graphene was thoroughly characterized with Raman spectroscopy, Atomic Force Microscopy, and X-ray photoelectron spectroscopy. Fabricated large area graphene-based field effect transistors exhibited high mobilities, which were about 2 times higher than those for devices prepared with graphene transferred by the conventional wet transfer method. This new graphene transfer technique has the potential to expedite the large scale industrial utilization of CVD graphene in electronics, spintronics, catalysis and energy storage.

Advances in the chemical vapor deposition (CVD) growth of graphene have made this material a very attractive candidate for a number of applications including transparent conductors, electronics, optoeletronics, biomedical devices and energy storage. The CVD method requires transfer of graphene on a desired substrate and this is most commonly accomplished with polymers. The removal of polymer carriers is achieved with organic solvents or thermal treatment which makes this approach inappropriate for application to plastic thin films such as polyethylene terephthalate substrates. An ultraclean graphene transfer method under mild conditions is highly desired. In this article, we report a naphthalene-assisted graphene transfer technique which provides a reliable route to residue-free transfer of graphene to both hard and flexible substrates. The quality of the transferred graphene was characterized with atomic force microscopy, scanning electron microscopy, and Raman spectroscopy. Field effect transistors, based on the naphthalene-transfered graphene, were fabricated and characterized. This work has the potential to broaden the applications of CVD graphene in fields where ultraclean graphene and mild graphene transfer conditions are required.

Adhesive bonding for composite structures offers multiple advantages over traditional fasteners such as reducing the weight, creating a more uniformly distributed stress state in the joint, and elimination of stress concentration factors due to joining. However, the strength of adhesive bonds can be reduced due to environmental exposure, contamination, mechanical damage and fatigue and assurances of long-term durability and bond strength are not available. Before adhesive bonding of composites can be used on primary structures, a method for guaranteeing the bonds strength must be developed. Due to magneto-electric principles, magneto-electric nanoparticles (MENs) can be used to detect minute changes of electric fields at the molecular level through detectable changes of the nanoparticles’ magnetization. As a result, when integrated into epoxy based adhesives, MENs are capable of detecting chemical or mechanical induced material imperfections at the molecular level. Current efforts are focused on developing a field tool that can be used to obtain magnetic signatures from doped adhesives similar to those obtained via laboratory scale equipment (vibrating sample magnetometer). To achieve similar sensitivities, FIU is investigating the use of a B-H looper system. In this approach, the MENs material is probed with a specifically designed setup that includes small electric coils wrapped around the sample. The coils are arranged into a noisecancellation configuration to measure the magnetic susceptibility of the sample under various conditions with a lock-in amplifier. With the goal to identify signature response characteristics of specific environmental and mechanical effects, various epoxy based adhesive samples were doped with 30 nm diameter MENs. Differences in magnetic signatures were observed between environmentally aged samples and baseline samples, demonstrating the viability of the B-H looper system as a bond inspection tool.