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Hall effect measurements in doped polymer semiconductors are widely reported, but are difficult to interpret due to screening of Hall voltages by carriers undergoing incoherent transport. Here, we propose a refined analysis for such Hall measurements, based on measuring the Hall coefficient as a function of temperature, and modelling carriers as existing in a regime of variable "deflectability" (i.e. how strongly they "feel" the magnetic part of the Lorentz force). By linearly interpolating each carrier between the extremes of no deflection and full deflection, we demonstrate that it is possible to extract the (time-averaged) concentration of deflectable charge carriers, $\left$, the average, temperature-dependent mobility of those carriers, $\left(T)$, as well as the ratio of conductivity that comes from such deflectable transport, $d(T)$. Our method was enabled by the construction of an improved AC Hall measurement system, as well as an improved data extraction method. We measured Hall bar devices of ion-exchange doped films of PBTTT-C$_{14}$ from 10--300 K. Our analysis provides evidence for the proportion of conductivity arising from deflectable transport, $d(T)$, increasing with doping level, ranging between 15.4% and 16.4% at room temperature. When compared to total charge-carrier-density estimates from independent methods, the values of $\left$ extracted suggest that carriers spend $\sim$37% of their time of flight being deflectable in the most highly doped of the devices measured here. The extracted values of $d(T)$ being less than half this value thus suggest that the limiting factor for conductivity in such highly doped devices is carrier mobility, rather than concentration., Comment: Accepted for publication in APS Physical Review Materials

Doped organic semiconductors are critical to emerging device applications, including thermoelectrics, bioelectronics, and neuromorphic computing devices. It is commonly assumed that low conductivities in these materials result primarily from charge trapping by the Coulomb potentials of the dopant counterions. Here, we present a combined experimental and theoretical study rebutting this belief. Using a newly developed doping technique based on ion exchange, we prepare highly doped films with several counterions of varying size and shape and characterize their carrier density, electrical conductivity, and paracrystalline disorder. In this uniquely large data set composed of several classes of high-mobility conjugated polymers, each doped with at least five different ions, we find electrical conductivity to be strongly correlated with paracrystalline disorder but poorly correlated with ionic size, suggesting that Coulomb traps do not limit transport. A general model for interacting electrons in highly doped polymers is proposed and carefully parametrized against atomistic calculations, enabling the calculation of electrical conductivity within the framework of transient localization theory. Theoretical calculations are in excellent agreement with experimental data, providing insights into the disorder-limited nature of charge transport and suggesting new strategies to further improve conductivities.

The charge transport–limiting factors in conjugated polymers without single-bond linkages in the backbone have been identified., We investigate the charge transport physics of a previously unidentified class of electron-deficient conjugated polymers that do not contain any single bonds linking monomer units along the backbone but only double-bond linkages. Such polymers would be expected to behave as rigid rods, but little is known about their actual chain conformations and electronic structure. Here, we present a detailed study of the structural and charge transport properties of a family of four such polymers. By adopting a copolymer design, we achieve high electron mobilities up to 0.5 cm2 V−1 s−1. Field-induced electron spin resonance measurements of charge dynamics provide evidence for relatively slow hopping over, however, long distances. Our work provides important insights into the factors that limit charge transport in this unique class of polymers and allows us to identify molecular design strategies for achieving even higher levels of performance.

Organic thermoelectrics offer the potential to deliver flexible, low-cost devices that can directly convert heat to electricity. Previous studies have reported high conductivity and thermoelectric power factor in the conjugated polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT). Here, we investigate the thermoelectric properties of PBTTT films in which the polymer chains were aligned uniaxially by mechanical rubbing, and the films were doped by a recently developed ion exchange technique that provides a choice over the counterions incorporated into the film, allowing for more optimized morphology and better stability than conventional charge transfer doping. To optimize the polymer alignment process, we took advantage of two Design of Experiment (DOE) techniques: regular two-level factorial design and central composite design. Rubbing temperature Trub and post-alignment annealing temperature Tanneal were the two factors that were most strongly correlated with conductivity. We were able to achieve high polymer alignment with a dichroic ratio >15 and high electrical conductivities of up to 4345 S/cm for transport parallel to the polymer chains, demonstrating that the ion exchange method can achieve conductivities comparable/higher than conventional charge transfer doping. While the conductivity of aligned films increased by a factor of 4 compared to unaligned films, the Seebeck coefficient (S) remained nearly unchanged. The combination of DOE methodology, high-temperature rubbing, and ion exchange doping provides a systematic, controllable strategy to tune structure–thermoelectric property relationships in semiconducting polymers.

Molecular doping—the use of redox‐active small molecules as dopants for organic semiconductors—has seen a surge in research interest driven by emerging applications in sensing, bioelectronics, and thermoelectrics. However, molecular doping carries with it several intrinsic problems stemming directly from the redox‐active character of these materials. A recent breakthrough was a doping technique based on ion‐exchange, which separates the redox and charge compensation steps of the doping process. Here, the equilibrium and kinetics of ion exchange doping in a model system, poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno(3,2‐b)thiophene) (PBTTT) doped with FeCl3 and an ionic liquid, is studied, reaching conductivities in excess of 1000 S cm−1 and ion exchange efficiencies above 99%. Several factors that enable such high performance, including the choice of acetonitrile as the doping solvent, which largely eliminates electrolyte association effects and dramatically increases the doping strength of FeCl3, are demonstrated. In this high ion exchange efficiency regime, a simple connection between electrochemical doping and ion exchange is illustrated, and it is shown that the performance and stability of highly doped PBTTT is ultimately limited by intrinsically poor stability at high redox potential.

We report the use of perfluoropolyether (PFPE) as a liquid dielectric for use in rubrene single-crystal transistors. In particular, we explore the effect of the free, permanent dipoles in PFPE on the charge carrier accumulation and transport at the rubrene/PFPE interface. This provides a complementary approach to ionic liquid dielectrics where charge accumulation is achieved via mobile ions. Large hysteresis (i.e., a memory effect) in transistor transfer curves and peaks in the gate displacement current curves are observed and interpreted in terms of the dipolar response of PFPE to the gate electric field. The orientation of free dipoles in PFPE is found to have a significant influence on the formation and annihilation of the rubrene conducting channel. Hole densities on the order of 1011 cm–2 are achieved at the surface of rubrene, and a transition from band-like to hopping transport near the freezing point of PFPE is evidenced by temperature-dependent Hall effect and resistance measurements. Overall, th...

Tellurene is a recently discovered 2D material with high hole mobility and air stability, rendering it a good candidate for future applications in electronics, optoelectronics, and energy devices. However, the physical properties of tellurene remain poorly understood. In this paper, we report on the fabrication and characterization of high-performance electrolyte-gated transistors (EGTs) based on solution-grown tellurene flakes30 nm in thickness. Both Hall measurements and resistance-temperature behavior down to 2 K are recorded at multiple gate voltages, and an electronic phase diagram is generated. The results show that it is possible to cross the insulator-metal transition in tellurene EGTs by tuning gate voltage, achieving mobility up to ∼500 cm

The authors gratefully acknowledge financial support by the Engineering and Physical Sciences Research Council (EPSRC) through a program grant (EP/M005143/1) and by the European Research Council (ERC) through a Synergy grant (SC2 610115).

Although electrolyte gating has been demonstrated to enable control of electronic phase transitions in many materials, long sought-after gate-induced insulator-metal transitions in organic semiconductors remain elusive. To better understand limiting factors in this regard, here we report detailed wide-range resistance-temperature ( R- T) measurements at multiple gate voltages on ionic-liquid-gated rubrene single crystals. Focusing on the previously observed high-bias regime where conductance anomalously decreases with increasing bias magnitude, we uncover two surprising (and related) features. First, distinctly cooling-rate-dependent transport is detected for the first time. Second, power law R- T is observed over a significant T window, which is highly unusual in an insulator. These features are discussed in terms of electronic disorder at the rubrene/ionic liquid interface influenced by (i) cooling-rate-dependent structural order in the ionic liquid and (ii) the intriguing possibility of a gate-induced glassy short-range charge-ordered state in rubrene. These results expose new physics at the gated rubrene surface, pointing to exciting new directions in the field.

International audience; have revealed the simultaneous presence of both high room temperature hole mobility above 10 cm 2 V −1 s −1[5] and, crucially , a negative temperature exponent for the mobility, i.e., mobility increases as temperature decreases down to about 180 K. [6] These observations and others, including mobility anisotropy [7,8] and a robust Hall effect, [9,10] are strong evidence for band-like transport in rubrene (band-width ≈0.5 eV), [11] where many features of classical band transport are observed. However, the estimated carrier mean free paths remain on the order of the unit cell dimension (≈1 nm), thus precluding the typical band picture in conventional semiconductors. The precise nature of band-like transport in organic semiconductor crystals is still being explored. [12] Currently, a consistent picture of charge transport in high mobility crystals is offered by the dynamic disorder model (DDM, also known as transient localization), in which the carrier transient localization length l loc and the propagation rate ω are determined by a competition between intermolecular electronic coupling and charge-phonon interaction ; in this scenario the carrier mobility μ can be evaluated as [13] µ ω = B loc 2 e k T l (1) Isotopic substitution is a useful method to study the influence of nuclear motion on the kinetics of charge transport in semiconductors. However, in organic semiconductors, no observable isotope effect on field-effect mobility has been reported. To understand the charge transport mechanism in rubrene, the benchmark organic semiconductor, crystals of fully isotopically substituted rubrene, 13 C-rubrene (13 C 42 H 28), are synthesized and characterized. Vapor-grown 13 C-rubrene single crystals have the same crystal structure and quality as native rubrene crystals (i.e., rubrene with a natural abundance of carbon isotopes). The characteristic transport signatures of rubrene, including room temperature hole mobility over 10 cm 2 V −1 s −1 , intrinsic band-like transport, and clear Hall behavior in the accumulation layer of air-gap transistors, are also observed for 13 C-rubrene crystals. The field-effect mobility distributions based on 74 rubrene and 13 C-rubrene devices, respectively, reveal that 13 C isotopic substitution produces a 13% reduction in the hole mobility of rubrene. The origin of the negative isotope effect is linked to the redshift of vibrational frequencies after 13 C-substitution, as demonstrated by computer simulations based on the transient localization (dynamic disorder) scenario. Overall, the data and analysis provide an important benchmark for ongoing efforts to understand transport in ordered organic semiconductors.

Haemophilus parasuis can cause a severe membrane inflammation disorder. It has been documented that superoxide dismutase (SOD) is a potential target to treat systemic inflammatory diseases. Therefore, we constructed an experimental H. parasuis subunit vaccine SOD and determined the protective efficacy of SOD using a lethal dose challenge against H. parasuis serovar 4 strain MD0322 and serovar 5 strain SH0165 in a mouse model. The results demonstrated that SOD could induce a strong humoral immune response in mice and provide significant immunoprotection efficacy against a lethal dose of H. parasuis serovar 4 strain MD0322 or serovar 5 strain SH0165 challenge. IgG subtype analysis indicated SOD protein could trigger a bias toward a Th1-type immune response and induce the proliferation of splenocytes and secretion of IL-2 and IFN-γ of splenocytes. In addition, serum in mice from the SOD-immunized group could inhibit the growth of strain MD0322 and strain SH0165 in the whole-blood killing bacteria assay. This is the first report that immunization of mice with SOD protein could provide protective effect against a lethal dose of H. parasuis serovar 4 and serovar 5 challenge in mice, which may provide a novel approach against heterogeneous serovar infection of H. parasuis in future.

z We reported that Zn x Cd 1− x S (ZnCdS) nanorods could be synthesized via a facile, nontoxic one-pot method. Structural and optical properties of ZnCdS nanorods were characterized by relevant equipments. The x value (Zn/(Zn+Cd)) could be altered across the entire range from 0.21 to 0.89 by changing the ratio of cation precursor contents. The band gap energy ( E g ) could be tuned linearly from 2.68 eV to 3.59 eV with respect to x . We also performed first-principles calculations to prove the experimental variation trend of band gap energy. Results showed that the replacement between Zn and Cd influenced the distribution of the electronic structure, and therefore determined the band gap energy.

It is of great necessity to explore a method to seek for a wrecked plane in the sea. In this paper we think of a static situation and establish a model that can be applied to quickly search the plane fallen into different oceans. Firstly, we develop a parabola model to simulate the process of plane falling. Take the projection of where the plane finally signaled on the sea as the center, and the distance between the two signaling positions plus the horizontal distance of the parabolic movement as radius, we can initially define the most likely falling area. Secondly, we apply Kruskal minimal spanning tree algorithm to minimize the total searching route. Then we regard suspicious neighboring goals as a single zone in different ways and each plane searches only one zone. Considering time cost and fuel cost, a multi- objective programming model is established to optimize the searching scheme. Finally we obtain the minimum cost and time for the whole searching.

* Corresponding author Abstract—We construct an evaluation system of sustainable development countries using the method of Bayes, k-means. Based on the classification, the developing model can be categorized into self-sufficient, technology-dependent and fund- dependent countries. We also explores the sustainable development of Equatorial Guinea. Finally, we evaluate the effect of sustainability plan and highly effective strategies.

* Corresponding author Abstract—In order to search the wreckage, this paper establish the particle network model, in terms of Monte Carlo simulation method and the Bayesian theory. Based on analytic inverse extrapolation, we use Monte Carlo simulation method to simulate thousands of particles and the distribution of the aircraft crash position. According to the relationship between the successful search probability, the depth of seabed, and the size of crashed plane, the model is developed. We get the successful search probability in each grid. Based on Bayesian theory and above probability distribution, we renew the probability distribution in each grid, if no wreckage is found after the search is completed. To ensure the largest success probability for each search, we find the wreckage in the least time. In this paper, we set several positions of the wreckage. In this method to search 16 times, we minimize the total search area.

People have payed more and more attention to biomass energy as the problem of energy is becoming serious. Biomass power generation is an important application of biomass energy. Because the basis and condition of biomass power generation are different in different regions, a reasonable risk evalution can help them to find their correct orientations. In this paper, ten indexes from five subsystems are chosen to do single subsystem risk evaluation, comprehensive evaluation and coordination degree evaluation respectively. According to the evaluating results, both the advantage and deficiency are pointed out in different regions in China.

Electronic disorder in organic semiconductor single crystals, manifested as parallel surface potential domains with potential variations ranging from tens to hundreds of mV, is observed by scanning Kelvin probe microscopy. Chemical etching and X-ray diffraction indicate that the potential domains are correlated with planar defects such as stacking faults. The results have important implications for understanding structure–transport relationships in organic semiconductor single crystals.

Ordered ZnO nanotube arrays with ultrathin wall embedded in anodic aluminum oxide (AAO) template were fabricated by electrodepositing Zn in the templates and then oxidizing them. The formation of Zn nanotubes is attributed to the annular Au electrode and the proper relative rates of deposition and diffusion of Zn 2+ ions. X-ray diffraction and selected-area electron diffraction analyses show that the ZnO nanotubes are polycrystalline. Scanning electron microscopy shows the nanotubes are of large area and have high aspect ratio. Transmission electron microscopy indicates that the ZnO nanotube is straight and has uniform thickness along the length, and the approximate thickness of the tube wall is 5 nm which is very close to the Bohr radius, 2.34 nm.

In this paper, we demonstrate that ZnxCd1?xSe nanomultipods can be synthesized via a facile and nontoxic solution-based method. Interesting aspects of composition, morphology and optical properties were deeply explored. The value of Zn/(Zn+Cd) could be altered across the entire range from 0.08 to 0.86 by varying the ratio of cation precursor contents. The band gap energy could be linearly tuned from 1.88 to 2.48?eV with respect to the value of Zn/(Zn+Cd). The experiment also showed that oleylamine played a dominant role in the formation of multipod structure. A possible growth mechanism was further suggested. First-principles calculations of band gap energy and density of states in the Vienna ab initio simulation package code were performed to verify the experimental variation tendency of the band gap. Computational results indicated that dissimilarities of electronic band structures and orbital constitutions determined the tunable band gap of the as-synthesized nanomultipod, which might be promising for versatile applications in relevant areas of solar cells, biomedicine, sensors, catalysts and so on.

We have reported that the Sn-doped PbSe nanocrystals could be synthesized via a facile solution-based method. Structural and optical characterizations were employed to investigate the properties of the nanocrystals. The x value could be altered across the entire range from 0.58 to 1 by modulating the ratio of cation precursor contents. The band gap energy of the Sn-doped PbSe nanocrystals could be tuned and changed in a nearly linearly way with respect to the x value. Furthermore, using oleylamine as the solvent promoted the nanocrystals to self-assemble as nano-flowers. The theoretical analysis based on first-principles calculations and density of states (DOS) in the VASP code demonstrates the validity of the experimentally obtained band gap variation and values. The band gap energy values at the edge of the solar spectrum render them as competitive candidates for solar applications.

Large-area free-standing arrays of TiO(2) nanorods and nanotubes were selectively synthesized on transparent conducting indium tin oxide substrates using sol-gel electrophoresis and anodic alumina (AAO) thin film templates. The effect of sol-gel ageing on the growth of TiO(2) was explained, providing a tailored ability to produce nanotubes and nanorods. An annular tungsten base electrode, stemming from the anodization of the AAO template, was found to be crucial to the growth of nanotubes. This was supported by a study of substrate annealing in a reducing atmosphere. The work can be readily adapted for the fabrication of free-standing arrays of other metal, metal oxide, and complex oxide nanorod and nanotube arrays on conducting substrates.