Improvement Of Electrical Properties Research Articles

Achieving high thermoelectric performance through carrier concentration optimization and energy filtering in Cu3SbSe4-based materials

The previous works commonly adjust the carrier concentration through acceptor doping, but at the same time, the decrease of the Seebeck coefficient limits the further improvement of electrical properties in Cu3SbSe4-based materials. In this work, a microwave-assisted hydrothermal synthesis method was used to synthesize Cu3SbSe4/TiO2 hollow microspheres. Part of TiO2 participates in the reaction, replaces the Sb site of Cu3SbSe4 to form holes, and the rest is dispersed in the matrix in the form of the second phase. The first-principles calculations reveal that the doping of Ti significantly changes the band structure and phonon spectrum, thereby regulating carrier concentration while increasing phonon scattering. In addition, experimental results show that the energy filtering effect generated by the extra-mixed TiO2 nano particles, which suppresses the decrease of Seebeck coefficient by acceptor doping. Consequently, the highest average power factor 897.5 μW m−1 K−2 and the zT peak value of 0.70 can be obtained in Cu3SbSe4/6%TiO2 sample at 298–623 K. This work provides a new sight to improve the thermoelectric properties in Cu3SbSe4 through carrier concentration regulation and nano-phase composition.

The conductive network optimization of composite graphite plates and its morphological analysis

The improvement of the conductivity and mechanical properties of composite graphite bipolar plates is critical for the performance optimization of proton exchange membrane fuel cells (PEMFC). However, it is difficult to achieve the balance of the conductivity and mechanical properties. An important element is that the resin deposits between graphite layers, resulting in weakened interconnection between the graphite layers, and this structure feature is directly related to the graphite and resin mixing process. In this study, a continuous conductive network was established to optimize the performance of composite graphite plates by developing the infiltration methods, which involved graphite plates preforming and resin infiltration (FGP-I). The conductive network was constructed preferentially through the preforming of graphite plates, which decreased the adverse effects of resin on the graphite connection during the mixing process. The conductivity of FGP-I was 322.64 S/cm at a resin content of 25 wt%, which was higher than that of the composite graphite plate made from the mixture of graphite and resin (FGP-M). The flexural strength of FGP-I was 86.95 MPa, higher than 57.97 MPa for FGP-M and 22.66 MPa for the flexible graphite infiltrated plates. And its helium permeability was 1.1*10-6 cm3·cm−2·s−1. The cross-section analysis and the density measurement confirmed that FGP-I possessed a more sufficient graphite conductive network and less structural defect, which were crucial factors to improve the composite plate performance. FGP-I was a viable candidate for composite bipolar plate preparation because the preparation method was straightforward and favorable to the balanced improvement of electrical conductivity and mechanical properties.

Simultaneous Improvement of Electrical and Thermal Transport Properties of Titanium Oxide Ceramic Thermoelectric Materials

Simultaneous Improvement of Electrical and Thermal Transport Properties of Titanium Oxide Ceramic Thermoelectric Materials

Effect of hybrid carbon nanofillers at percolation on electrical and mechanical properties of glass fiber reinforced epoxy

AbstractMulti walled carbon nanotubes and graphene nanoplatelets are novel fillers possessing exceptional intrinsic characteristics, such as high aspect ratio, strength, and good compatibility. These fillers are integrated into a glass fiber reinforced epoxy using a pultrusion process with a mixing ratio of 2:3 to attain the synergetic effect. The electrical and mechanical properties of the composites containing combinations of multi walled carbon nanotubes (0.4 wt%), graphene nanoplatelets (0.6 wt%) and micron aluminum trihydrate (2 wt%) fillers is studied. Significant improvement in electrical and mechanical properties is achieved. This study reveals that the incorporation of hybrid carbon nanofillers into epoxy leads to improved dielectric constant, AC conductivity and mechanical properties as compared with the base epoxy composite with glass reinforcement. The AC conductivity increases from 10−9 to 10−1 S/m and dielectric constant from 3.6 to 100 due to carbon fillers. The mean tensile strength improves from 433 MPa of the base epoxy composite to 508 MPa in carbon‐filled composite. The compressive strength improves from 630 to 681 MPa due to incorporation of carbon fillers signifying the improvement in load transfer effectiveness. The effect of carbon fillers on the flexural strength and hardness is minimal. The experimental data on mechanical parameters have been validated using theoretical modeling and a good correlation is established.

Improved light trapping and electrical properties from ZnO:Al seed layer/Ag nanowires/ZnO:Al nanorods composite structure for transparent conducting films

A novel ZnO:Al seed layer/Ag nanowires/ZnO:Al nanorods (AZO SL/Ag NWs/AZO NRs) composite structure for transparent conducting films was successfully obtained to enhance the light trapping and electrical properties concurrently. The morphology of Ag NWs and AZO NRs interlaced composite structure on the AZO SL was observed. Compared with the simplex AZO SL/AZO NRs films, the films with AZO SL/Ag NWs/AZO NRs composite structure had lower average sheet resistance (13.8 Ω/sq) and higher haze value (0.33) at 550 nm, which exhibited the effective improvement of both electrical and light trapping properties. The studies on the AZO SL/Ag NWs/AZO NR composite films in this work provide a novel structure for transparent conducting films applied in solar cells.

Influence of thermal treatment on electronic properties of inkjet-printed zinc oxide semiconductor

ABSTRACT Additive manufacturing of electronic devices using inkjet printing provides a potential alternative approach in substitution for conventional electronic fabrication processes. However, the complex nature of inkjet printing involves the liquid deposition and film formation from the vaporization of solvent, which makes it different from film created by conventional deposition methods. Inkjet printing of zinc oxide (ZnO), which is a widely utilized semiconductor, produces polycrystalline film composed of nano-size grains, which could significantly influence the properties of printed film. In this study, low-temperature annealing was employed to treat inkjet-printed ZnO for UV photodetection application, and its influence on electrical properties was studied. Band bending was characterized using the Mott-Schottky plot which examines the charge distribution of the films. It is found that the annealing of inkjet-printed polycrystalline ZnO film has improved its electrical properties, which could be attributed to the reduction of band bending due to the merging of grains. The treatment also helps to reduce impurities of the film, such as zinc hydroxide complexes, which are common for solution-derived films. Hence, the study could pay the way for the improvement of electrical properties of inkjet-printed functional materials.

Improvement in electrical and mechanical properties of di/trifunctional epoxies-based hybrid composites having metal organic frameworks (MOFs) as nanoparticulate filler

Improvement in electrical and mechanical properties of di/trifunctional epoxies-based hybrid composites having metal organic frameworks (MOFs) as nanoparticulate filler

Achieving multiband compatible and mechanical tuning absorber using edge topological defect-induced graphene plasmon

Graphene has been shown to be a high-performance microwave-absorbing material with broadband potential. However, simultaneous realization of multiband compatible strong absorption is still a challenge. In this study, graphene rich in edge topological defects is successfully synthesized, and the effect of defect density on electromagnetic parameters has been investigated. Electrons (π electrons, π+σ electrons) located at edge defects alter the loss paths and plasma absorption frequencies of the graphene aerogels. These improvements in electrical properties give the graphene aerogel a more coordinated impedance matching and attenuation capability, allowing it to achieve strong absorption in multiband (S, X, Ku band) simultaneously. In addition, a mechanically tunable multimode absorber can be further realized by incorporating porous polyimide foam. The strong absorption (>99.9%) of a wide range of variable bands (S, C, X, and Ku bands) can be flexibly adjusted by stress cycling of piezo resistive foam. In addition, self-cleaning, high temperature resistance, and simple processability are expected to deliver solutions for the communication and Internet of Things engineering.

Toward Reduced Interface Contact Resistance: Controllable Surface Energy of Sb2Te3 Films via Tuning the Crystallization and Orientation.

The electrical contact resistance between a metal and semiconductor is one of the keys to improving the output performance of thin-film thermoelectric devices. Herein, we reduced the interface contact resistance by controlling the surface energy of a Sb2Te3 semiconductor via tuning of the crystallization and orientation, preparing an intrinsically compact and flat Sb2Te3 film with high surface energy and low roughness, which can give rise to a low average specific contact resistivity (8.2 × 10-6 Ω cm2) with a Ni/Cu metal. The improvement in interface electrical properties is due to the increase in the surface energy and decrease in the surface roughness of the semiconductor surface, which lead to a transformation from three-dimensional island-shaped nucleation to two-dimensional layered nucleation for surface-attached metal films, forming a longitudinally tight connection contact with a low resistance. This approach allows the resistivity to become close to the fundamental theoretically calculated limit. Our work provides a new idea for reducing the contact resistivity of thin-film thermoelectric devices, which is conducive to supporting the development of thermoelectric semiconductor planarization.

Surface etching evolution of mechanically polished single crystal diamond with subsurface cleavage in microwave hydrogen plasma: Topography, state and electrical properties

Surface etching of single-crystal diamond (SCD) in hydrogen plasma plays a decisive role for high-quality homoepitaxy and surface conduction of diamond. The complexity of surface/subsurface condition such as defects would give rise to the distinct morphology features and even further result in the unpredictable properties. Correspondingly, the evolutionary relationship between the morphology and electrical properties of mechanically polished SCDs which have typical cleavage damage in microns depth after hydrogen plasma treatment still needs to be further completed. In this work, the chemical vapor deposited (CVD) SCDs with uniform polishing-caused subsurface cleavage were immersed in microwave hydrogen plasma for variable duration. Time-dependent morphological evolution, multi-mode etched pits (EPs) (resulting from local defects/cracks and dislocations) and associated etching mechanism were comprehensively studied. At the early stage of plasma treatment before 60 min, owing to the obvious surface roughing generated by preferential etching (with the rate of >400 nm/h) of severe mechanically damaged regions, the hole mobility was significantly deteriorated, also accompanying with the apparent drop of sheet concentration. Concurrently, the deposited surface sp2 amorphous carbon (a-C) nanodots on diamond surface and non-sp3 hydrogen bonds reconstruction, which arising from defect-etching produced local abundant carbon-containing radicals or possible exfoliation generated by hydrogen penetration of massive defective regions, also would play an adverse role for the conduction associated with (100) C–H surface. However, the surface roughness was reduced from the maximum 13.2 nm–4.2 nm by prolonging etching, resulting from the smoothing effect of small-angle crystal misorientation on waved height difference related to the uniform (111) cleavage and the removal of dense irregular EPs associated with polishing-induced local defects as well as the vanishing of surface a-C nanodots. In this case, the improvement of surface electrical properties together with the negative correlation of the mobility and sheet concentration were appeared by the gradual formation of (100) diamond surface and the building of uniform (100) C–H bonds.

Investigations of Fused Deposition Modeling for Perovskite Active Solar Cells.

The advent of Fused Deposition Modeling (FDM; or 3D printing) has significantly changed the way many products are designed and built. It has even opened opportunities to fabricate new products on-site and on-demand. In addition, parallel efforts that introduce new materials into the FDM process have seen great advances as well. New additives have been demonstrably utilized to achieve thermal, electrical, and structural property improvements. This combination of fabrication flexibility and material additives make FDM an ideal candidate for investigation of perovskite materials in new solar cell efforts. In this work, we fabricate and characterize a perovskite-based solar cell polymer designed for the FDM fabrication processes. Perovskite solar cells have garnered major research interest since their discovery in 2009. Perovskites, specifically methylammonium lead iodide, offer beneficial properties to solar cell fabrication such as long minority charge carrier distance, high light absorption, and simple fabrication methods. Despite the great potential of these materials, however, stability remains an issue in solar cell utilization as the material degrades under ultraviolet light, exposure to oxygen and water, as well as increased temperatures. To mitigate degradation, different fabrication methods have been utilized. Additionally, multiple groups have utilized encapsulation methods post-fabrication and in situ solution processed integration of polymer materials into the solar cell to prevent degradation. In this paper, we leverage the unique ability of FDM to encapsulate perovskite materials and yield a MAPbI3-PCL solar material as the active layer for solar cell use. In this manner, increased ability to resist UV light degradation and material stability from other environmental factors can be achieved. This study provides characterization of the material via multiple techniques like SEM (Scanning Electron Microscopy) and XRD (X-ray Diffraction) as well as absorbance, transmittance, and photocurrent response. Investigations of processing on perovskite degradation as well as initial solar simulated response are recorded. Unique aspects of the resulting material and process are noted including improved performance with increased operating temperature. Increased electron–hole pair generation is observed for 200 m FDM-printed PCL film, achieving a 45% reduction in resistance under peak incident flux of 590 W/m with the addition of MAPbl3. This work establishes insight into the use of FDM for full solar cell fabrication and points to the next steps of research and development in this growing field.

Simultaneous Improvement of Leakage, Electric, and Magneto-Dielectric Properties Due to the Reduction in Grain Size

Simultaneous Improvement of Leakage, Electric, and Magneto-Dielectric Properties Due to the Reduction in Grain Size

Improvement of Electrical Property of Printed TiO2 Thin Film by the Mixture of Small and Large Particle Size Using LDM 3D-Printing System

Improvement of Electrical Property of Printed TiO₂ Thin Film by the Mixture of Small and Large Particle Size Using LDM 3D-Printing System

Spray deposited gallium doped zinc oxide (GZO) thin film as the electron transport layer in inverted organic solar cells

The electric field-assisted spray deposition of highly conducting and transparent gallium doped zinc oxide (GZO) films, with noticeable improvement in optical, structural, and electrical properties, is reported for application in organic photovoltaics with superior device performance. The GZO films deposited with applied voltages of 0 and 2000V to the nozzle exhibited an improved electrical resistivity of ∼1.8 × 10−3 Ω-cm and a transmittance (in the visible region) of over 80% for the films deposited under electric field, which can be used as electron transport layer (ETL) in inverted organic solar cells (IOSCs- ITO/GZO/PTB7:PC71BM/MoO3/Ag). Improved photovoltaic performance (power conversion efficiency: 6.5%) is obtained for the IOSC devices fabricated GZO ETL with the applied voltage of 2000V in comparison to the device fabricated using GZO ETL with the applied voltage = 0V (power conversion efficiency: 5.8%).

Effect of rapid thermal treatment on the electrical conductivity improvement of nc-ZnO:Bi thin film and ITO substrate

Spherical nano crystalline zinc oxide doped with bismuth (nc-ZnO:Bi) spin-coated on indium tin oxide (ITO) substrates exhibited the improvement of conductivity under the rapid thermal annealing (RTA) treatment. The ZnO:Bi nanostructure was formed at 550 °C annealing temperature, which severely affect the ITO electrical quality and closely relevant with the device performance. The efficiency of relevant electronic devices has been limited by the low electrical conductivity of the transparent electrodes. RTA treatment in the ambient atmosphere condition was applied to ZnO:Bi film coated on ITO substrate to perform the good spherical nc-ZnO:Bi properties and to persist in the ITO low resistivity, concomitantly which results in significant improvement of electrical and optical properties of nc-ZnO:Bi/ITO substrate. RTA process was subjected at varying temperature conditions from 700 °C to 930 °C for 20 s. It is noticeable that the RTA can obtain ZnO:Bi nanostructure, good optical property, and high ITO conductivity existence, simultaneously. The nano-spherical ZnO:Bi around 10–20nm diameter size at the film surface morphology provides the reflectance of 6%, and the transmittance of above 90% at 930 °C RTA for 20 s. The photocurrent of nc-ZnO:Bi/ITO films provides between 10−2 to 1 A/cm2 at 0.5 V. The RTA process can improve electrical property of ITO films with uniform distribution of oxygen vacancy. Surface morphology and crystalline grain quality of the thin film were investigated after RTA treatment. In addition, optical absorbance and energy gap (Eg) of nc-ZnO:Bi/ITO substrate evaluated by Tauc plot is a crucial attribute to apply in a promising photonic device. Thus, the high electrical and optical qualities of such nc-ZnO:Bi/ITO films can be used to produce an electron transport layer for organic solar cells and transparent contact electrodes for low-cost semiconductor devices.

Nanocomposite Conductive Bioinks Based on Low-Concentration GelMA and MXene Nanosheets/Gold Nanoparticles Providing Enhanced Printability of Functional Skeletal Muscle Tissues.

There is a growing need to develop novel well-characterized biological inks (bioinks) that are customizable for three-dimensional (3D) bioprinting of specific tissue types. Gelatin methacryloyl (GelMA) is one such candidate bioink due to its biocompatibility and tunable mechanical properties. Currently, only low-concentration GelMA hydrogels (≤5% w/v) are suitable as cell-laden bioinks, allowing high cell viability, elongation, and migration. Yet, they offer poor printability. Herein, we optimize GelMA bioinks in terms of concentration and cross-linking time for improved skeletal muscle C2C12 cell spreading in 3D, and we augment these by adding gold nanoparticles (AuNPs) or a two-dimensional (2D) transition metal carbide (MXene nanosheets) for enhanced printability and biological properties. AuNP and MXene addition endowed GelMA with increased conductivity (up to 0.8 ± 0.07 and 0.9 ± 0.12 S/m, respectively, compared to 0.3 ± 0.06 S/m for pure GelMA). Furthermore, it resulted in an improvement of rheological properties and printability, specifically at 10 °C. Improvements in electrical and rheological properties led to enhanced differentiation of encapsulated myoblasts and allowed for printing highly viable (97%) stable constructs. Taken together, these results constitute a significant step toward fabrication of 3D conductive tissue constructs with physiological relevance.

InSnZnO Thin-Film Transistors With Nitrogenous Self-Assembled Multilayers Passivation

Nitrogenous octadecylamine (ODA) self-assembled multilayers (SAMs) are prepared as passivation layers by the vapor-phase process for amorphous InSnZnO (ITZO) thin-film transistors (TFTs). The vapor-phase proposed ODA SAMs show excellent properties as a barrier against the atmosphere and serve as an effective nitrogen doping (N doping) source. After the self-assembled process, the distribution of the oxygen vacancies is modified by N-doping in the channel of the ITZO TFTs, wherefore the ITZO TFTs with ODA SAMs demonstrate an improvement of electrical properties. In addition, the oxygen and water adsorption/desorption reactions at the back channel are suppressed by the atmosphere isolation and N-doping effect, leading to an improvement of the positive bias stability. These results indicate that the nitrogenous ODA SAMs can be likely passivation layers for high-performance oxide TFT devices.

Piezoresistive sensor for human motion detection based on polyaniline decorated thermally exfoliated graphene oxide

The rigidity and discomfort associated with the use of conventional semiconductor-based wearable devices has prompted increasing interest in hydrogel-based devices. Hydrogels have properties similar to human skin tissue and therefore are more comfortable to use. The present study reports a high-performance, piezoresistive hydrogel nanocomposite-based wearable device towards human motion sensing. The nanocomposites comprise of an optimized distribution of polyaniline (PANI) decorated thermally exfoliated graphene oxide (TEGO) nanofillers incorporated within a biopolymer matrix. The engineered nanofillers endow the hydrogel with synergistic improvement in mechanical and electrical properties, resulting in a combination of high electrical conductance and extraordinary mechanical performance. The material demonstrated high stability during fatigue cycling done for extended periods. Furthermore, these nanostructured materials were used to prepare wearable sensors towards human motion detection. These advanced sensors exhibit a stable, sensitive and repeatable electrical response. Moreover, the use of fully biodegradable raw materials, simple synthesis method, and easy scalability establish the significant potential of the developed material towards wearable devices.

Heteroepitaxial Growth of High Optical Quality, Wafer-Scale van der Waals Heterostrucutres.

Transition metal dichalcogenides (TMDs) are materials that can exhibit intriguing optical properties like a change of the bandgap from indirect to direct when being thinned down to a monolayer. Well-resolved narrow excitonic resonances can be observed for such monolayers although only for materials of sufficient crystalline quality and so far mostly available in the form of micrometer-sized flakes. A further significant improvement of optical and electrical properties can be achieved by transferring the TMD on hexagonal boron nitride (hBN). To exploit the full potential of TMDs in future applications, epitaxial techniques have to be developed that not only allow the growth of large-scale, high-quality TMD monolayers but also allow the growth to be performed directly on large-scale epitaxial hBN. In this work, we address this problem and demonstrate that MoSe2 of high optical quality can be directly grown on epitaxial hBN on an entire 2 in. wafer. We developed a combined growth theme for which hBN is first synthesized at high temperature by metal organic vapor phase epitaxy (MOVPE) and as a second step MoSe2 is deposited on top by molecular beam epitaxy (MBE) at much lower temperatures. We show that this structure exhibits excellent optical properties, manifested by narrow excitonic lines in the photoluminescence spectra. Moreover, the material is homogeneous on the area of the whole 2 in. wafer with only ±0.14 meV deviation of excitonic energy. Our mixed growth technique may guide the way for future large-scale production of high quality TMD/hBN heterostructures.

Superior energy storage performance coupled with excellent electrical characteristics in lead-free Ba0.8Ca0.2TiO3-(Bi0.80Mg0.20) (Ti0.65Mg0.30)O3 ceramics

Multi-layer ceramic capacitors with high recoverable energy storage density and large energy efficiency play a crucial in modern electronic devices. Various ferroelectric ceramic materials with relaxor characteristics and large dielectric constant are the most favorable candidates for achieving superior energy storage performance. Herein, a novel lead-free (1−x)Ba0.80Ca0.20TiO3-x (Bi0.80Mg0.20)(Ti0.65Mg0.30)O3 (BCT-BMT) ceramic materials were prepared by two-stage mechano-chemical activation technique. BMT substitution in Ca modified BaTiO3 has resulted in substantial improvement in microstructural characteristics and subsequently an improvement in energy storage performance in comparison to pure BCT. The introduction of BMT in BCT has resulted in transformation into relaxor ceramics, which is vital for obtaining high recoverable energy storage density and large energy efficiency. In the present investigation, the composition with 0.65BCT-0.35BMT shows a typical relaxor characteristic, large breakdown strength, and a substantially large dielectric constant. As a result of improvement in electrical properties, the composition 0.65BCT-0.35BMT possesses an ultra-high recoverable energy density of 3.09 J cm−3 along with a moderately high energy efficiency of ∼80.15%. The obtained results indicate the effectiveness of BMT substitution on the energy storage properties and excellent compatibility between BCT and BMT phases.