Composite Semiconductor Research Articles

Tacky Elastomers to Enable Tear‐Resistant and Autonomous Self‐Healing Semiconductor Composites

AbstractMechanical failure of π‐conjugated polymer thin films is unavoidable under cyclic loading conditions, due to intrinsic defects and poor resistance to crack propagation. Here, the first tear‐resistant and room‐temperature self‐healable semiconducting composite is presented, consisting of conjugated polymers and butyl rubber elastomers. This new composite displays both a record‐low elastic modulus (<1 MPa) and ultrahigh deformability with fracture strain above 800%. More importantly, failure behavior is not sensitive to precut notches under deformation. Autonomous self‐healing at room temperature, both mechanical and electronic, is demonstrated through the physical contact of two separate films. The composite film also shows device stability in the ambient environment over 5 months due to much‐improved barrier property to both oxygen and water. Butyl rubber is broadly applicable to various p‐type and n‐type semiconducting polymers for fabricating self‐healable electronics to provide new resilient electronics that mimic the tear resistance and healable property of human skin.

Carbonate dual-phase improves the performance of single-layer fuel cell made from mixed ionic and semiconductor composite

A mixed ionic and semiconducting composite in a single-layer configuration has been shown to work as a fuel cell at a lower temperature (500–600 °C) than a traditional solid-oxide fuel cell. The performance of a single-layer fuel cell (SLFC) is often limited by high resistive losses. Here, a eutectic mixture of alkali-carbonates was added to SLFC to improve the ionic conductivity. The dual-phase composite ionic conductor consisted of a ternary carbonate (sodium lithium potassium carbonate, NLKC) mixed with gadolinium-doped cerium oxide (GDC). Lithium nickel zinc oxide (LNZ) was used as the semiconducting material. The LNZ-GDC-NLKC SLFC reached a high power density, 582 mW/cm2 (conductivity 0.22 S/cm) at 600 °C, which is 30 times better than without the carbonate. The best results were obtained with the ternary carbonate which decreased the ohmic losses of the cell by more than 95%, whereas the SLFC with a binary carbonate (sodium lithium carbonate, NLC) showed a lower conductivity and performance (243 mW/cm2, 0.17 S/cm at 600 °C). It is concluded that adding carbonates to LNZ-GDC will improve the ionic conductivity and positively contribute to the cell performance. These results suggest a potential path for further development of SLFCs, but also imply the need for efforts on up-scaling and stability to produce practical applications with SLFC.

Novel p-n heterojunction of BiVO4/Cu2O decorated with rGO for low concentration of NO2 detection

NO2 is a toxic gas that can cause photochemical smog, acid rain and ozone layer depletion. The reduced graphene oxide (rGO) decorated nanocomposites of semiconductor metal oxides (MOS) as sensing materials of NO2 sensors have received much attention. Here, BiVO4/Cu2O/rGO nanocomposite was successfully prepared by a facile solvothermal method and thermal reduction method. The gas-sensing test indicates that the response of optimum nanocomposite to 1 ppm NO2 is 8 times higher than the pure BiVO4 and 5 times higher than the p-n heterojunction of BiVO4/Cu2O, respectively at 60 °C operating temperature. The response time and recovery time also shortened compared to pure BiVO4 and BiVO4/Cu2O composite, and this composite has better stability for detection of NO2, which benefits from the superimposed effect of p-n heterojunction formation and rGO decoration. This work can provide reference for improving the sensing properties of metal oxide semiconductor composites for detection of NO2.

Photocatalytic applications of graphene based semiconductor composites: A review

Photocatalysis has proven its virtue as an emerging area of research since its discovery. In the primary stages of research, semiconductors like TiO2, ZnO, PtO2 etc. have been used to carry out various photocatalytic processes such as hydrogen energy generation, water treatment, conversion of CO2 to energy fuels, microbial disinfection and organic transformations. Though these semiconductors had a great potential in them, high rate of recombination of charge carriers has allegedly been reported to minimize their expected photocatalytic yield. In the recent era graphene has attracted so many eyes owing to its magical properties like ultrafast electron transport, higher specific surface area, higher rate of adsorption, high mechanical strength, chemical and thermal stability. Introduction of graphene to couple with semiconductor photocatalysts helped in increasing the efficiency of pristine semiconductors to many folds. Being a two-dimensional nano material with a greater number of trapping site, it holds the semiconductors very strongly. The π-conjugated electronic structure makes it an ultimate electron acceptor. Graphene transfers the accepted electrons very quickly and easily because of its zero-bandgap structure. By virtue of such fascinating properties, it separates the photogenerated electrons from the semiconductor to reduce the recombination of charge carriers. In this work, we have focussed on synthesis strategies of grapheme based semiconductor photocatalysts and reviewed briefly their diversified photocatalytic applications.

Absorption and temperature distribution during ultrafast laser microcutting of polymeric materials

Material processing by ultrafast lasers is an attractive technology for high-precision fabrication, such as cutting, drilling, and surface modification, of a wide range of material, including dielectrics, semiconductor, metals, and polymer composites. However, it is still challenging to apply ultrafast laser processing in many applications because some key processes, such as absorption and heat accumulation, are not fully understood, especially for polymeric materials, which have a low melting temperature and, therefore, are more vulnerable to thermal damage. In this study, an analytical solution to a transient, two-dimensional thermal model is derived using Duhamel's theorem and Hankel’s transform method to understand the effect of laser parameters during ultrafast laser interactions with polypropylene (PP), which is a material widely used in many industrial applications. To correlate with theoretical calculation, laser cutting experiments are carried out on PP sheets. This study found that the total energy absorbed in the material and the laser intensity are two important factors to estimate the laser processing performance. In addition, time-resolved measurements are performed by using fast photodiodes and an oscilloscope to understand the dynamics of ultrafast laser interactions during the laser cutting process. Transmitted and reflected signals are monitored and analyzed to extract information on nonlinearity and the absorption coefficient.

Research on Life Prediction of IGBT Devices Based on Elman Neural Network Model

IGBT, as a new generation of composite full-controlled voltage-driven power semiconductor devices, has been widely used in the field of modern power electronics. The study of IGBT device life prediction has important guiding significance for the stable operation and reliability management of power system. In this paper, the Cofin-Manson-Arrhenius extended exponential model based on thermal load is analyzed, and the model parameters are trained and modified by the Elman neural network in order to improve the prediction accuracy of life prediction model. The Coffin-Manson-Arrhenius extension exponential model and the new improved model are simulated and validated by experiments. The results are compared with the actual life of IGBT. It is concluded that the Coffin-Manson-Arrhenius extension exponential model based on Elman neural network has higher accuracy in life prediction than the Coffin-Manson-Arrhenius extension exponential model.

Synthesis and characterization of a composite organic semiconductor (curcumin-paracetamol/TiO2)

The aim of this work is to study some physical and chemical properties of an organic semiconductor (OSc)/ x%titanium dioxide (TiO2) heterosystem (with 0 ≤ x ≤ 20%) (OScs/ x%TiO2). The OSc is obtained from pure curcumin and paracetamol as starting molecules. The synthesis methodology of the mixtures of OScs/ x%TiO2 heterosystem involves a microwave-assisted multicomponent reaction using curcumin, paracetamol, and TiO2 as a heterogeneous solution. All mixtures were analyzed by Fourier-transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis/differential thermal analysis, X-ray diffraction, ultraviolet–visible spectroscopy, and scanning electron microscopy. The results obtained show a new nanocomposite with interesting pharmaceutical, optical, electronic, and structural properties, which can be used in the fields of energy production, water purification, and air purification, as a biomaterial and for electronic applications.

Electrical Response of a Multiferroic Composite Semiconductor Fiber Under a Local Magnetic Field

We study the electrical response of a multiferroic composite semiconductor fiber consisting of a piezoelectric semiconductor layer and two piezomagnetic layers under a transverse magnetic field applied locally to a finite part of the fiber. The phenomenological theory of piezomagnetic-piezoelectric semiconductors is employed. A one-dimensional model is derived for magnetically induced extension of the fiber. For open-circuit boundary conditions at the two ends of the fiber, an analytical solution is obtained from the model linearized for small carrier perturbations. The solution shows a local electric polarization and a pair of local electric potential barrier-well. When the two ends of the fiber are under a voltage, a nonlinear numerical solution shows that the potential barrier and well forbid the passage of currents when the voltage is low. The results have potential applications in piezotronic devices when magnetic fields are involved for manipulating the devices or sensing and transduction.

TiO2/ZrO2 Nanoparticle Composites for Electrochemical Hydrogen Evolution

Composites of different semiconductors are found to show much improved electronic conductivity and decreased charge transfer resistance. In this work, this hypothesis is tested by preparing composi...

Photocatalytic reduction of CO2 to methanol over ZnFe2O4/TiO2 (p–n) heterojunctions under visible light irradiation

AbstractBACKGROUNDThe development of visible light photocatalysts for CO2 reduction into methanol is a challenge, as most of the reported photocatalysts can only work in a UV light environment. Slow kinetics and poor selectivity of CO2 towards methanol are currently two significant drawbacks limiting the practical application of CO2 reduction into methanol.RESULTSA ZnFe2O4/TiO2 heterojunction with a ratio of unity was found to lead to the highest methanol yield of 693.31 μmol (g cat)−1 under a light intensity of 100 mW cm−2. This photocatalyst also possessed the highest BET surface area of 6.5211 m2 g−1 and better morphological structure, as compared with other ratios (1:2, 2:1 w/w). Interestingly, a loading of 1 g L−1 of ZnFe2O4/TiO2 (1:1) heterojunction photocatalyst in the pre‐annealing treatment of ZnFe2O4 at 900 °C and post‐annealing treatment of ZnFe2O4/TiO2 (1:1) composite at 500 °C revealed that there was an enhancement in the interfacial interaction, and subsequently an efficient photoreduction of CO2 into methanol.CONCLUSIONSThis study demonstrates facile fabrication of p–n heterostructured phototcatalysts for reduction of CO2 with marked improvement in methanol yield under visible light irradiation. It provides a viable route for exploring the effects of composition, hydrothermal treatment, and pre‐/post‐annealing treatment of hybrid semiconductor composites used to scale up photocatalytic CO2 conversion in solar fuel‐based devices.

BiVO4 /Bi4Ti3O12 heterojunction enabling efficient photocatalytic reduction of CO2 with H2O to CH3OH and CO

Construction of composite semiconductors is an effective solution to elevate the efficiency of photocatalysis by prolonging lifetime of photogenerated hole and electrons. Herein, a heterojunction structure composite BiVO4/Bi4Ti3O12 was synthesized via a facile in situ hydrothermal condition. The novel composite photocatalyst has excellent photocatalytic ability to reduce CO2 with H2O into CH3OH and CO. The BiVO4/10 % Bi4Ti3O12 sample shows the highest yields of CH3OH and CO up to 16.6 and 13.29 μmol g−1 h−1, which was 12.39 and 5.68 times higher than that of pure BiVO4, and 9.88 and 2.80 times higher than that of pure Bi4Ti3O12, respectively. Such a high activity is attributed to the type II heterojunction structure which significantly enhances separation of photogenerated carriers and promotes collaboration between the water oxidation on the Bi4Ti3O12 and the CO2 reduction on BiVO4. The photocatalytic reaction mechanism of CO2 on the composite was proposed according to experiment results.

Influence of Additives on Zinc Oxide-Based Dye Sensitized Solar Cells

Abstract In order to enhance the power conversation efficiency of dye sensitized solar cells (DSSCs), various trials have been reported. In this work, composites of n-type semiconductors, ZnO and ZrS2 were fabricated in DSSCs. In addition, the effect of addition of carbon dots on them was assessed. When 10 wt% of ZrS2 was mixed with ZnO, the power conversion efficiency achieved 1.6 times of that of ZnO but the coexistence of carbon dots and ZrS2 in ZnO DSSC resulted the decrease of the power conversion efficiency. ZrS2 forms an n-n heterojunction with ZnO and contributes to the fast transfer of electrons to the conductive electrode substrate. Meanwhile, when carbon dots are added to ZnO/ZrS2(10 wt%) DSSC, the electrons generated and transferred to ZrS2 should recombine with holes generated and transferred to photosensitizer. These situations are compared with a composite system of ZnO/carbon dots previously reported and suggest us the selection of preferable combinations of composite DSSCs.

A Wearable Toxic Gas‐Monitoring Device Based on Triboelectric Nanogenerator for Self‐Powered Aniline Early Warning

AbstractWith the increasingly serious air pollution and rapid progress in nanotechnology, portable and wearable sensing devices are becoming indispensable to people's lives. The triboelectric nanogenerator (TENG) captures wide attention due to its safe, highly efficient, and environmentally friendly way to drive portable electronics. In this work, by adjusting the doping ratio and optimizing the annealing temperature, a new kind of low‐resistant rGO–In2O3 semiconductor composite is synthesized and innovatively used as TENG electrode. The as‐fabricated rGO‐In2O3‐TENG is used as a monitoring unit and exhibits advantages of excellent linear sensibility (200–1200 ppm), good response (∆I/Ia = 0.26, 600 ppm), and outstanding selectivity toward aniline toxic gas. More importantly, compared with the common room‐temperature semiconductor gas sensor, the self‐powered rGO‐In2O3‐TENG monitoring unit is endowed with much shorter response/recovery time. By combining rGO‐In2O3‐TENG monitoring unit, conversion circuit, and visualization warning lights, a visual wearable aniline early‐warning device is fabricated. The present results provide a novel idea for developing a new type of aniline sensor with self‐powered property of low cost and portability, and may also be extended to the design of other toxic gases‐monitoring system.

Multifunctional poly(N-methylpyrrole)/nano-oxide composites: Optoelectronic, charge transport and antibacterial properties

This study reports structural, charge transport and antibacterial properties of Poly(N-methylpyrrole) (PNMPy) and its composites. Optical studies indicated that both indium(III) oxide (In2O3) and tungsten(VI) oxide (WO3) nanoparticles increased the optical band gap of PNMPy. Furthermore, it was determined that the filling process increased the fluorescence quantum yield of PNMPy from 0.19 to 0.23 and 0.32 for PNMPy/In2O3 and PNMPy/WO3 composites, respectively. Two different frequency regions were observed for the conductivity in the temperature dependent dielectric analysis. Alternating conductivity analysis indicated that the dominant mechanism for the charge transport was the hopping type and the most suitable model was the correlated barrier hopping (CBH) model for PNMPy and its composites. While, In2O3 nanoparticles increased the hopping distance as well as the activation energy required for the hopping of the charge carriers in the polymer matrix, in contrast, WO3 nanoparticles decreased them. Both nanoparticles improved the thermal stability and antibacterial activity of the polymer matrix. PNMPy/In2O3 and PNMPy/WO3 semiconductor composites could be used not only in electronics and optoelectronics applications in the mid-frequency range but also in biomedical applications as they have also exhibited excellent antibacterial properties.

PN junctions with coupling to bending deformation in composite piezoelectric semiconductor fibers

We demonstrate through a theoretical analysis that a PN junction in a composite fiber consisting of a nonpiezoelectric semiconductor layer between two piezoelectric dielectric layers is electromechanically coupled to the bending deformation of the fiber. This offers new ways for constructing piezotronic device structures. A one-dimensional model based on the macroscopic theory of piezoelectric semiconductors is used in the analysis. The built-in electric potential and electric field, the bending deformation of the fiber, and other electromechanical fields near the junction are obtained. The effects of the doping level, thickness ratio of different layers, and material combination of the composite fiber are examined.

Reduced graphene oxide-porous In2O3 nanocubes hybrid nanocomposites for room-temperature NH3 sensing

Metal oxide semiconductors (MOS)-reduced graphene oxide (rGO) nanocomposites have attracted great attention for room-temperature gas sensing applications. The development of novel sensing materials is the key issue for the effective detection of ammoniagas at room temperature. In the present work, the novel reduced graphene oxide (rGO)-In2O3 nanocubes hybrid materials have been prepared via a simple electrostatic self-assembly strategy. Characterization results exhibit that the intimate interfacial contact between In2O3 nanocubes and the rGO sheets are achieved. Particularly, the as-prepared rGO/In2O3 nanocomposites displayed high sensitivity, fast response and excellent selectivity towards ammonia (NH3) at room-temperature, which clearly uncovers the merit of structural design and rational integration with rGO sheets. The superior gas sensing performance of the rGO/In2O3 nanocomposites can be attributed to the synergetic effects of rGO sheets and porous In2O3 nanocubes. The reported synthesis offers a general approach to rGO/MOS-based semiconductor composites for room-temperature gas sensing applications.

Control of the Synthesis and Composition of Semiconductors. Low-Defect Silicon Carbide and Low-Dimensional Cadmium Selenide

The details of the controlled synthesis and basic performances determining the properties of the semiconductor substances—composition, structure, size and morphology of the particles forming them—were discussed. The nontrivial, but important for the functional use of semiconductors, criteria of purity and homogeneity were expressed. The noted details of the materiology of semiconductors were discussed with the example of the synthesis of low-defect wafers of silicon carbide, and also low-dimensional powders of cadmium selenide.

Nano-assemblies of a soluble conjugated organic polymer and an inorganic semiconductor for sacrificial photocatalytic hydrogen production from water.

Nanostructured materials have interesting optical and electronic properties that are often drastically different from those of their bulk counterparts. While bulk organic/inorganic semiconductor composites have attracted much attention in the past decade, the preparation of organic/inorganic semiconductor nanocomposites (OISNs) still remains challenging. This work presents an assembly method for the co-encapsulation of titanium dioxide dots (TDs) with a cyano-substituted soluble conjugated polymer (CSCP) into a particular nanoparticle. The as-prepared CSCP/TD semiconductor nanocomposites (CSCP/TD NCs) exhibit different particle surfaces and morphologies depending on the mass ratio of the CSCP to TDs. We then tested them as photocatalysts for sacrificial hydrogen production from water. We found that nanocomposites outperformed nanoparticles of the individual components and physical mixtures thereof. The most active CSCP/TD NC had a catalytic H2 production rate that was 4.25 times higher than that of pure polymer nanoparticles prepared under the same conditions. We ascribe this to energy transfer between the semiconductors, where direct phase contact is essential, highlighting a potential avenue for using soluble, visible light-absorbing conjugated organic polymers to build Z-schemes for overall water splitting in the future.

Evaluation of different Ni–semiconductor composites as electrodes for enhanced hydrogen evolution reaction

A series of Ni–semiconductor composites are electrodeposited onto low-cost stainless-steel plates and used as electrodes for hydrogen generation from water; showing superb electrocatalytic activity over time.

Fluorescence studies and photocatalytic application for hydrogen production of ZnII and CdII complexes with isophthaloylbis(thioureas)

TiO2-based semiconductor composites containing ZnII and CdII complexes produced more hydrogen gas than pure TiO2.