Recent advances in fabrication and functions of neuromorphic system based on organic field effect transistor

The development of various artificial electronics and machines would explosively increase the amount of information and data,which need to be processed via in-situ remediation.Bioinspired synapse devices can store and process signals in a parallel way,thus improving fault tolerance and decreasing the power consumption of artificial systems.The organic field effect transistor(OFET)is a promising component for bioinspired neuromorphic systems because it is suitable for large-scale integrated circuits and flexible devices.In this review,the organic semiconductor materials,structures and fabrication,and different artificial sensory perception systems functions based on neuromorphic OFET devices are summarized.Subsequently,a summary and challenges of neuromorphic OFET devices are provided.This review presents a detailed introduction to the recent progress of neuromorphic OFET devices from semiconductor materials to perception systems,which would serve as a reference for the development of neuromorphic systems in future bioinspired electronics.

Partners selection of VE based on the organizational field

VE organizational field is a management meaning field formed by the mutual action of resources element.It studies leader and partners in VE as a system,and founds the affiliation among them by the relation of resources.It describes candidate partner enterprise's inner trait and exterior trait by quality parameter and exterior parameter,then analyzes and evaluates them.It combines the qualitative variable and quantitative variable to evaluate the candidate enterprises.It integrates static and dynamic method to help the VE leader to choose partner,which is good for the whole alliance.

Large-scale Tazhong Ordovician Reef-flat Oil-Gas Field in the Tarim Basin of China

The Tazhong reef-fiat oil-gas field is the first large-scale Ordovician organic reef type oil-gas field found in China. Its organic reefs were developed in the early Late Ordovician Lianglitag Formation, and are the first large reefs of the coral-stromatoporoid hermatypic community found in China. The organic reefs and platform-margin grain banks constitute a reef-flat complex, mainly consisting of biolithites and grainstones. The biolithites can be classified into the framestone, baffiestone, bindstone etc. The main body of the complex lies around the wells from Tazhong-24 to Tazhong-82, trending northwest, with the thickness from 100 to 300 m, length about 220 km and width 5-10 km. It is a reef-flat lithologic hydrocarbon reservoir, with a very complex hydrocarbon distribution： being a gas condensate reservoir as a whole with local oil reservoirs. The hydrocarbon distribution is controlled by the reef complex, generally located in the upper 100-200 m part of the complex, and largely in a banded shape along the complex. On the profile, the reservoir shows a stratified feature, with an altitude difference of almost 2200 m from southeast to northwest. The petroleum accumulation is controlled by karst reservoir beds and the northeast strike-slip fault belt. The total geologic reserves had reached 297.667 Mt by 2007.

Top contact organic field effect transistors fabricated using a photolithographic process

This paper proposes an effective method of fabricating top contact organic field effect transistors by using a pho- tolithographic process. The semiconductor layer is protected by a passivation layer. Through photolithographic and etching processes, parts of the passivation layer are etched off to form source/drain electrode patterns. Combined with conventional evaporation and lift-off techniques, organic field effect transistors with a top contact are fabricated suc- cessfully, whose properties are comparable to those prepared with the shadow mask method and one order of magnitude higher than the bottom contact devices fabricated by using a photolithographic process.

A Fractional Drift Diffusion Model for Organic Semiconductor Devices

Because charge carriers of many organic semiconductors(OSCs)exhibit fractional drift diffusion(Fr-DD)transport properties,the need to develop a Fr-DD model solver becomes more apparent.However,the current research on solving the governing equations of the Fr-DD model is practically nonexistent.In this paper,an iterative solver with high precision is developed to solve both the transient and steady-state Fr-DD model for organic semiconductor devices.The Fr-DD model is composed of two fractionalorder carriers(i.e.,electrons and holes)continuity equations coupled with Poisson’s equation.By treating the current density as constants within each pair of consecutive grid nodes,a linear Caputo’s fractional-order ordinary differential equation(FrODE)can be produced,and its analytic solution gives an approximation to the carrier concentration.The convergence of the solver is guaranteed by implementing a successive over-relaxation(SOR)mechanism on each loop of Gummel’s iteration.Based on our derivations,it can be shown that the Scharfetter–Gummel discretization method is essentially a special case of our scheme.In addition,the consistency and convergence of the two core algorithms are proved,with three numerical examples designed to demonstrate the accuracy and computational performance of this solver.Finally,we validate the Fr-DD model for a steady-state organic field effect transistor(OFET)by fitting the simulated transconductance and output curves to the experimental data.

Progress in organic spintronics

Recent progress in organic spintronics is given an informative overview, covering spin injection, detection, and trans-port in organic spin valve devices, and the magnetic field effect in organic semiconductors （OSCs）. In particular, we focus on our own recent work in spin injection and the organic magnetic field effect （OMFE）.

The inversion of density structure by graphic processing unit(GPU) and identification of igneous rocks in Xisha area

Organic reefs, the targets of deep-water petro- leum exploration, developed widely in Xisha area. However, there are concealed igneous rocks undersea, to which organic rocks have nearly equal wave impedance. So the igneous rocks have become interference for future explo- ration by having similar seismic reflection characteristics. Yet, the density and magnetism of organic reefs are very different from igneous rocks. It has obvious advantages to identify organic reefs and igneous rocks by gravity and magnetic data. At first, frequency decomposition was applied to the free-air gravity anomaly in Xisha area to obtain the 2D subdivision of the gravity anomaly and magnetic anomaly in the vertical direction. Thus, the dis- tribution of igneous rocks in the horizontal direction can be acquired according to high-frequency field, low-frequency field, and its physical properties. Then, 3D forward model- ing of gravitational field was carried out to establish the density model of this area by reference to physical properties of rocks based on former researches. Furthermore, 3D inversion of gravity anomaly by genetic algorithm method of the graphic processing unit （GPU） parallel processing in Xisha target area was applied, and 3D density structure of this area was obtained. By this way, we can confine the igneous rocks to the certain depth according to the density of the igneous rocks. The frequency decomposition and 3D inversion of gravity anomaly by genetic algorithm method of the GPU parallel processing proved to be a useful method for recognizing igneous rocks to its 3D geological position. So organic reefs and igneous rocks can be identified, which provide a prescient information for further exploration.

Highly crystalline,highly stable n-type ultrathin crystalline films enabled by solution blending strategy toward organic single-crystal electronics

The development of n-type semiconductor is still far behind that of p-type semiconductor on account of the challenges in enhancing carrier mobility and environmental stability.Herein,by blending with the polymers,n-type ultrathin crystalline thin film was successfully prepared by the method of meniscus-guided coating.Remarkably,the n-type crystalline films exhibit ultrathin thickness as low as 5 nm and excellent mobility of 1.58 cm^(2) V^(-1) s^(-1),which is outstanding in currently reported organic n-type transistors.Moreover,the PS layer provides a high-quality interface with ultralow defect which has strong resistance to external interference with excellent long-term stability,paving the way for the application of n-type transistors in logic circuits.

Enhanced performance of C60 organic field effect transistors using a tris(8-hydroxyquinoline) aluminum buffer layer

We have investigated the properties of C60-based organic field effect transistors（OFETs） with a tris（8- hydroxyquinoline） aluminum（Alq3） buffer layer inserted between the source/drain electrodes and the active material. The electrical characteristics of OFETs are improved with the insertion of Alq3 film.The peak field effect mobility is increased to 1.28×10^（-2） cm^2/（V·s） and the threshold voltage is decreased to 10 V when the thickness of the Alq3 is 10 nm.The reason for the improved performance of the devices is probably due to the prevention of metal atoms diffusing into the C60 active layer and the reduction of the channel resistance in Alq3 films.

Research of organic field effect transistors based on semiconducting single-walled carbon nanotubes

The metal-conducting single-walled carbon nanotubes （m-SWNTs） with small diameters （0.7 nm-1.1 nm） are selectively removed from the single-walled carbon nanotubes （SWNTs） by using HNOJH2SO4 mixed solution. Semiconducting single- walled carbon nanotubes （s-SWNTs） can be separated efficiently from the SWNTs with high controllability and purity based on this novel method, and the outcome is characterized by Raman spectrum. Moreover, the organic field effect transistors （OFETs） are fabricated based on the poly （3-hexylthiophene-2, 5-diyl） （P3HT）, and untreated SWNTs and separated SWNTs （s-SWNTs） are mixed with P3HT, respectively. It could be found that the P3HT/s-SWNT device exhibits a better field effect characteristic compared with the P3HT device. The current on/off ratio is increased by 4 times, the threshold voltage is also increased from -28 V to -22 V, and the mobility is increased from 3 ~ 10.3 cmZNs to 5 x 10.3 cm2/Vs.

Nonideal double-slope effect in organic field-effect transistors

With the development of device engineering and molecular design,organic field effect transistors(OFETs)with high mobility over 10 cm2 V-1-s-1 have been reported.However,the nonideal doubleslope effect has been frequently observed in some of these OFETs,which makes it difficult to extract the intrinsic mobility OFETs accurately,impeding the further application of them.In this review,the origin of the nonideal double-slope effect has been discussed thoroughly,with affecting factors such as contact resistance,charge trapping,disorder effects and coulombic interactions considered.According to these discussions and the understanding of the mechanism behind double-slope effect,several strategies have been proposed to realize ideal OFETs,such as doping,molecular engineering,charge trapping reduction,and contact engineering.After that,some novel devices based on the nonideal double-slope behaviors have been also introduced.

Humidity sensitive organic field effect transistor

This paper reports the experimental results for the humidity dependent properties of an organic field effect transistor.The organic field effect transistor was fabricated on thoroughly cleaned glass substrate,in which the junction between the metal gate and the organic channel plays the role of gate dielectric.Thin films of organic semiconductor copper phthalocynanine（CuPc） and semitransparent Al were deposited in sequence by vacuum thermal evaporation on the glass substrate with preliminarily deposited Ag source and drain electrodes.The output and transfer characteristics of the fabricated device were performed.The effect of humidity on the drain current,drain current-drain voltage relationship, and threshold voltage was investigated.It was observed that humidity has a strong effect on the characteristics of the organic field effect transistor.

Performance enhancement of pentacene-based organic field-effect transistor by inserting a WO_3 buffer layer

The pentacene-based organic field effect transistor （OFET） with a thin transition metal oxide （WO3） layer between pentacene and metal （AI） source/drain electrodes was fabricated. Compared with conventional OFET with only metal AI source/drain electrodes, the introduction of the WO3 buffer layer leads to the device performance enhancement. The effective field-effect mobility and threshold voltage are improved to 1.90 em2/（V.s） and 13 V, respectively. The performance improvements are attributed to the decrease of the interface energy barrier and the contact resistance. The results indicate that it is an effective approach to improve the OFET performance by using a WO3 buffer layer.

Biogenic volatile organic compound analyses by PTR-TOF-MS: Calibration, humidity effect and reduced electric field dependency

Green leaf volatiles（GLVs） emitted by plants after stress or damage induction are a major part of biogenic volatile organic compounds（BVOCs）. Proton transfer reaction time-of-flight mass spectrometry（PTR-TOF-MS） is a high-resolution and sensitive technique for in situ GLV analyses, while its performance is dramatically influenced by humidity, electric field,etc. In this study the influence of gas humidity and the effect of reduced field（E/N） were examined in addition to measuring calibration curves for the GLVs. Calibration curves measured for seven of the GLVs in dry air were linear, with sensitivities ranging from 5 to10 ncps/ppbv（normalized counts per second/parts per billion by volume）. The sensitivities for most GLV analyses were found to increase by between 20% and 35% when the humidity of the sample gas was raised from 0% to 70% relative humidity（RH） at 21°C, with the exception of（E）-2-hexenol. Product ion branching ratios were also affected by humidity,with the relative abundance of the protonated molecular ions and higher mass fragment ions increasing with humidity. The effect of reduced field（E/N） on the fragmentation of GLVs was examined in the drift tube of the PTR-TOF-MS. The structurally similar GLVs are acutely susceptible to fragmentation following ionization and the fragmentation patterns are highly dependent on E/N. Overall the measured fragmentation patterns contain sufficient information to permit at least partial separation and identification of the isomeric GLVs by looking at differences in their fragmentation patterns at high and low E/N.

Cocrystal engineering:towards high-performance near-infrared organic phototransistors based on donor-acceptor charge transfer cocrystals

Near-infrared organic phototransistors have wide application prospects in many fields.The active materials with the high mobility and near-infrared response are critical to building high-performance near-infrared organic phototransistors,which are scarce at present.Herein,a new charge transfer cocrystal using 5,7-dihydroindolo[2,3-b]carbazole(5,7-ICZ)as the donor and 2,2’-(benzo[1,2-b:4,5-b’]dithiophene-4,8-diylidene)dimalononitrile(DTTCNQ)as the acceptor is properly designed and prepared in a stoichiometric ratio(D:A=1:1),which not only displays a high electron mobility of 0.15 cm^(2)V^(-1)s^(-1) and very low dark current,but also can serve as the active layer materials in the region of near-infrared detection due to the narrowed band gap and good charge transport properties.A high photosensitivity of 1.8×10^(4),the ultrahigh photoresponsivity of 2,923 A W-1and the high detectivity of 4.26×10^(11)Jones of the organic near-infrared phototransistors are obtained.

Well-balanced ambipolar diketopyrrolopyrrole-based copolymers for OFETs,inverters and frequency doublers

Conjugated polymers with well-balanced ambipolar charge transport is essential for organic circuits at low cost and large area with simplified fabrication techniques.Aiming at this point,herein,a novel asymmetric thiophene/pyridine-flanked diketopyrrolopyrrole-based copolymer(PPyTDPP-2FBT)is designed and synthesized.Due to the effect of incorporating F atoms on molecular energy alignment and conjugation conformation,the PPyTDPP-2FBT copolymer exhibits typical V-shaped ambipolar field-effect transfer characteristics with well-balanced hole and electron mobilities of 0.64 and 0.46 cm^(2)V^(−1)s^(−1),respectively.Furthermore,organic digital and analog circuits such as inverters and frequency doublers are successfully constructed based on solution-processed films of the PPyTDPP-2FBT copolymers which show a typical circuit operating mode with a high gain of 133 due to the well-balanced electrical properties.In addition,PPyTDPP-2FBT-based devices also demonstrate good stability and batch repeatability,suggesting their great potential applications in organic integrated electronic circuits.

Naphthalene diimide based near-infrared luminogens with aggregation-induced emission characteristics for biological imaging and high mobility ambipolar transistors

Organic conjugated materials combining high conductivity with strong solid-state emission are highly desired for organic electronic applications,yet still rather rare.Herein,a novel luminogen(TEN)comprised by linking naphthalene diimides and triphenyl ethylene with vinyl bridges is reported.TEN exhibits aggregation-induced emission(AIE)behavior of a strong nearinfrared fluorescence over 700 nm and the efficiency above 60.5%in the solid state,while also shows promising application in vivo bio-imaging with good permeability and extremely low background.Single crystal of TEN reveals intra-and intermolecular C–H…O hydrogen bonds,contributing to an inclined molecular stacking along the a-axis of the cell,creating a 1 D charge carrier transporting channel under a shortπ-πinteraction distance of 3.42?,which might benefit the solid emission and charge transport ability simultaneously.Solution processed bottom contact,top gate organic field effect transistors based on TEN reveal a high ambipolar charge transport ability with the hole mobility up to 0.13 cm2 V-1 s-1 and electron mobility up to0.010 cm2 V-1 s-1.Further atomic force microscopy and X-ray diffraction analysis on TEN thin film confirm the existence of the1 Dπ-πstacking channel,suggesting the stacking geometry revealed in crystal crucial for facilitating high charge carrier mobility while preserving the strong solid emission at the same time.

Extracting Parameters of OFET Before and After Threshold Voltage Using Genetic Algorithms

This paper presents a compact analytical model for the organic field-effect transistors （OFETs）, which describes two main aspects, the first one is related to the behavior in above threshold regime, while the other corresponds to the below threshold regime. The total drain current in the OFET device is calculated as the sum of two components, with the inclusion of a smooth transition function in order to take into account both regions using a single expression. A genetic algorithm based approach （GA） is investigated as a parameter extraction tool in the case of the compact OFET model to find the parameters＇ values from experimental data such as： mobility enhancement factor % threshold voltage VTh, subthreshold swing S, channel length modulation A, and knee region sharpness m. The comparison of the developed current model with the experimental data shows a good agreement in terms of the transfer and the output characteristics. Therefore, the GA based approach can be considered as a competitive candidate compared to the direct method.

Tuning the Charge Transport Property of Naphthalene Diimide Derivatives by Changing the Substituted Position of Fluorine Atom on Molecular Backbone

Three naphthalene diimides(2,3 and 4)fused with 2-(1,3-dithiol-2-ylidene)-2-fluorophenylacetonitrile moieties were designed and synthesized.Due to the different substituted positions of fluorine atom on the phenyl group,the solution-processed thin films of 2 and 3 operated in air as n-channel transistors,while the films of 4 performed as ambipolar transistors,indicating that the variation of substituted position of fluorine atom on molecular backbone may tune the material’s charge transport behavior.