Bright hybrid white light-emitting quantum dot device with direct charge injection into quantum dot

A bright white quantum dot light-emitting device （white-QLED） with 4-[4-（1-phenyl-lH-benzo[d]imidazol-2- yl）phenyl]-2- [3-（tri-phenylen-2-yl）phen-3-yl]quinazoline deposited on a thin film of mixed green/red-QDs as a bilayer emitter is fabricated. The optimized white-QLED exhibits a turn-on voltage of 3.2 V and a maximum brightness of 3660 cd/m2 @8 V with the Commission Internationale de l＇Eclairage （CIE） chromaticity in the region of white light. The ultra-thin layer of QDs is proved to be critical for the white light generation in the devices. Excitation mechanism in the white-QLEDs is investigated by the detailed analyses of electroluminescence （EL） spectral and the fluorescence lifetime of QDs. The results show that charge injection is a dominant mechanism of excitation in the white-QLED.

20 MHz Switched-Current Sample-and-Hold Circuit with Low Charge Injection

A switched-current sample-and-hold circuit with low charge injection was proposed. To obtain low noise and charge injection, the zero-voltage switching was used to remove the signal-dependent charge injection, and the signal-independent charge injection was reduced by removing the feed-through voltage from the input port of the memory transistor directly. This current sample-and-hold circuit was implemented using CMOS 180 nm 1.8 V technology. For a 0.8 MHz sinusoidal signal input, the simulated signal-to-noise and distortion ratio and total harmonic distortion were improved from 53.74 dB and -51.24 dB to 56.53 dB and -54.36 dB at the sampling rate of 20 MHz respectively, with accuracy of 9.01 bit and power consumption of 0.44 mW.

Photoinduced charge injection in the metal/organic interface studied by transient photovoltage measurements with bias

Transient photovoltage of ITO/organic/Al cells is studied under different bias polarities and voltages.It is found that for an ITO/NPB/Al cell,light incidence on the Al side induces more bias-dependent transient photovoltage variation when the photovoltage is positive than when it is negative.However,for an ITO/C60 /Al cell,the variation characteristics of transient photovoltage is reversed.These results support the previously proposed mechanism that Al could inject charges into the organic layer upon photon excitation,indicating that the absorption of electrode can also contribute to photovoltaic effect.

Green perovskite light-emitting diodes with simultaneous high luminance and quantum efficiency through charge injection engineering

Metal halide perovskite light emitting diodes(PeLEDs)have recently experienced rapid development due to the tunable emission wavelengths,narrow emission linewidth and low material cost.To achieve stateof-the-art performance,the high photoluminescence quantum yield(PLQY)of the active emission layer,the balanced charge injection,and the optimized optical extraction should be considered simultaneously.Multiple chemical passivation strategies have been provided as controllable and efficient methods to improve the PLQY of the perovskite layer.However,high luminance under large injection current and high external quantum efficiency(EQE)can hardly be achieved due to Auger recombination at high carrier density.Here,we decreased the electron injection barrier by tuning the Fermi-level of the perovskite,leading to a reduced turn on voltage.Through molecular doping of the hole injection material,a more balanced hole injection was achieved.At last,a device with modified charge injection realizes high luminance and quantum efficiency simultaneously.The best device exhibits luminance of 55,000 cd m^-2 EQE of 8.02%at the working voltage of 2.65 V,current density of 115 mA cm^-2,and shows EQE T50 stability around 160 min at 100 mA cm^-2 injection current density.

Evolution of Diagenetic Fluid of the Dawsonite-Bearing Sandstone in the Jiyang Depression,Eastern China

Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandstone is characterized by double injection of CO_(2)and oil-gas in the Jiyang Depression that have experienced a relatively complex diagenetic fluid evolution process.The diagenetic sequence of secondary minerals involves secondary enlargement of quartz,kaolinite,first-stage calcite,dawsonite,second-stage calcite,ferrocalcite,dolomite and ankerite.Hydrocarbon charging in the dawsonite-bearing sandstone occurred at around 2.6–0 Myr.The CO_(2)charging event occurred during Dongying tectonism,forming the Pingfangwang CO_(2)gas reservoir,which provided an abundant carbon source for dawsonite precipitation.Carbon and oxygen isotopic compositions of dawsonite demonstrate that CO_(2)forming the dawsonite was of an inorganic origin derived from the mantle,and that water mediating the proc-ess during dawsonite precipitation was sequestered brine with a fluid temperature of 82℃.The evolutionary sequence of the diagenetic fluid in the dawsonite-bearing sandstone was:alkaline syngenetic fluids,weak alkaline fluids during organic acid forma-tion,acidic fluids in the early stage of CO_(2)injection,alkaline fluids in the late stage of CO_(2)injection,and weak alkaline fluids during oil and gas charging.The mode indicates an increase in-HCO_(3)because of the CO_(2)injection,and the loss of Ca^(2+)and Mg^(2+)due to the precipitation of carbonate minerals.Therefore,the evolutionary mode of diagenetic fluids is in good agreement with high HCO_(3)^(-),low Ca^(2+)and low Mg^(2+)composition of the present formation water in the dawsonite-bearing sandstone.

A molecular cobaloxime cocatalyst and ultrathin FeOOH nanolayers co-modifiedBiVO_(4) photoanode for efficient photoelectrochemical water oxidation

BiVO_(4) has been attracting a lot of interest in photoelectrochemical (PEC) water oxidation due to its efficient solar absorption and appropriate band positions.So far,sluggish water oxidation kinetics and fast photogenerated charge recombination still hinder the PEC performance ofBiVO_(4) .In this study,a novel PEC photoanode was designed by depositing ultrathin FeOOH nanolayers on the surface of nanoporousBiVO_(4) electrode,followed by modification with a cobaloxime (Co(dmgH)_(2)(4-COOH-py)Cl) molecular cocatalyst.Under irradiation of a 100 mW cm^(-2)(AM 1.5G) Xe lamp,the photocurrent density of the cobaloxime/FeOOH/BiVO_(4) composite photoanode reached 5.1 mA cm^(-2)at 1.23 V vs.RHE in 1.0 M potassium borate buffer solution (pH=9.0).The onset potential of the optimal cobaloxime/FeOOH/BiVO_(4) photoanode exhibited a 460 m V cathodic shift relative to bareBiVO_(4) .In addition,the surface charge injection efficiency of the composite photoanode reached~80%at 1.23 V vs.RHE and the incident photon-to-current efficiency (IPCE) reached~88%at 420 nm.

Improved Performance of Organic Light-Emitting Diodes with MgF2 as the Anode Buffer Layer

Organic light-emitting diodes （OLEDs） based on N,N＇-bis（1-naphthyl）-N,N＇-diphenyl-1,l1＇-biphenyl-4,4＇-diamine （NPB） and tris （8-hydroxyquinoline） aluminium （Alq3 ） are improved by using a thin MgF2 buffer layer sandwiched between the indium tin oxide （ITO） anode and hole transporting layer （HTL） of NPB. The current-voltage curves of the OLEDs with MgF2 buffers shift to lower voltages, which can be explained by the tunnelling effect. Under 10 V bias, the current density and brightness for the optimized OLED with a 1.0-nm MgF2 are 196A/m^2 and 517cd/m^2, respectively, while for the OLED without anode buffer layer are only 109A/m^2 and 156cd/m^2, The atomic force microscopy shows that the rms roughness of NPB on ITO/MgF2 is only 1/3 of NPB on bare ITO. The improved morphology of the HTL would lead to more robust OLEDs. The OLED with a 1.0-nm MgF2 layer has a long lifetime of more than five times of the MgF2-free reference device due to the combined electrical and morphological effects of the MgF2 layer.

A hybrid model for the charging process of the amorphous SiO_2 film in radio frequency microelectromechanical system capacitive switches

Charging is one of the most important reliability issues in radio frequency microelectro- mechanical systems （RF MEMS） capacitive switches since it makes the actuation voltage unstable. This paper proposes a hybrid model to describe the transient dielectric charging and discharging process in the defect-rich amorphous SiO2 RF MEMS capacitive switches and verifies experimentally. The hybrid model contains two parts according to two different charging mechanisms of the amorphous SiO2, which are the polarisation and charge injection. The models for polarisation and for charge injection are established, respectively. Analysis and experimental results show that polarisation is always effective, while the charge injection has a threshold electric field to the amorphous SiO2 film. Under different control voltage conditions, the hybrid model can accurately describe the experimental data.

Ligand-controlled electrochemiluminescence generation from CdSe/CdS/ZnS core/shell/shell quantum dots

The CdSe/CdS/ZnS core/shell/shell quantum dots(QDs)with strong exciton confinement have manifested themselves as competitive light-emitting materials in electrochemiluminescence(ECL).However,cathodic ECL generation by these QDs requires the injection of electron and hole from solid electrode and electrogenerated radicals(for example SO_(4)•^(−)),which is inevitably influenced by not only the inorganic structure of QDs but also the organic ligands on the surface.In this work we aimed at studying the impact of surface organic ligands on ECL performance of CdSe/CdS/ZnS QDs.When changing the surface ligand from oleate to acetate,we phenomenologically observed the positive shift of ECL onset potential by ca.200 mV and the increase of ECL intensity by~100 times,suggesting that a short ligand is more favorable for ECL generation.To further comprehend the ligand effect,we measured the charge injection kinetics using potential-modulated,time-resolved photoluminescence,and thinlayer spectroelectrochemistry techniques.The electron and hole injection into QDs were found to be accelerated by 2–20 times if shortening the ligand from oleate to acetate,confirming the significant impact of surface ligands on ECL performance of QDs.The study is expected to provide guidance on how to design surface functionalized QDs for specific applications such as ECL immunodiagnosis,photocatalysis,and photovoltaics.

Enhanced photoresponse of Ti0_(2)/MoS_(2)heterostructure phototransistors by the coupling of interface charge transfer and photogating

Two-dimensional(2D)MoS_(2)with appealing physical properties is a promising candidate for next-generation electronic and optoelectronic devices,where the ultrathin MoS_(2)is usually laid on or gated by a dielectric oxide layer.The oxide/MoS_(2)interfaces widely existing in these devices have significant impacts on the carrier transport of the MoS_(2)channel by diverse interface interactions.Artificial design of the oxide/MoS_(2)interfaces would provide an effective way to break through the performance limit of the 2D devices but has yet been well explored.Here,we report a high-performance MoS_(2)-based phototransistor with an enhanced photoresponse by interfacing few-layer MoS_(2)with an ultrathin Ti0_(2)layer.The Ti0_(2)is deposited on MoS_(2)through the oxidation of an e-beam-evaporated ultrathin Ti layer.Upon a visible-light illumination,the fabricated Ti0_(2)/MoS_(2)phototransistor exhibits a responsivity of up to 2,199 A/W at a gate voltage of 60 V and a detectivity of up to 1.67×10^(13)Jones at a zero-gate voltage under a power density of 23.2μW/mm^(2).These values are 4.0 and 4.2 times those of the pure MoS_(2)phototransistor.The significantly enhanced photoresponse of Ti0_(2)/MoS_(2)device can be attributed to both interface charge transfer and photogating effects.Our results not only provide valuable insights into the interactions at Ti0_(2)/MoS_(2)interface,but also may inspire new approach to develop other novel optoelectronic devices based on 2D layered materials.

Understanding DC Partial Discharge:Recent Progress,Challenges,and Outlooks

As a non-destructive local gas breakdown phenomenon within a surface or bulk cavity surrounded by insulation,partial discharge(PD)contains important information which can be used to evaluate and diagnose electrical insulation systems.In this paper,distinctive characteristics of PD for DC versus AC are reviewed.A summary of experimental studies on DC PD in different insulation coordinations is presented,including PD in gaseous insulating media,PD in solid insulating media and PD in liquid insulating media.Conclusions and some thoughts based on existing studies are provided,and challenges and suggestions for future studies are given.This paper can serve as a guide reference for readers to learn the background and state-of-the-art of DC PD studies.More importantly,it is hopeful that this study can inspire novel ideas for further advancing fundamental research of DC PD mechanisms and PD mitigation methods.

Physics of electron emission and injection in two-dimensional materials: Theory and simulation

Electrically contacting two-dimensional(2D)materials is an inevitable process in the fabrication of devices for both the study of fundamental nanoscale charge transport physics and the design of high-performance novel electronic and optoelectronic devices.The physics of electrical contact formation and interfacial charge injection critically underlies the performance,energyefficiency and the functionality of 2D-material-based devices,thus representing one of the key factors in determining whether 2D materials can be successfully implemented as a new material basis for the development of nextgeneration beyond-silicon solid-state device technology.In this review,the recent developments in the theory and the computational simulation of electron emission,interfacial charge injection and electrical contact formation in 2D material interfaces,heterostructures,and devices are reviewed.Focusing on thermionic charge injection phenomena which are omnipresent in 2Dmaterials-based metal/semiconductor Schottky contacts,we summarize various transport models and scaling laws recently developed for 2D materials.Recent progress on the first-principle density functional theory simulation of 2D-material-based electrical contacts are also reviewed.This review aims to provide a crystalized summary on the physics of charge injection in the 2D Flatlands for bridging the theoretical and the experimental research communities of 2D material device physics and technology.

Anisotropic Plasmon Resonance Enables Spatially Controlled Photothermal and Photochemical Effects in Hot Carrier-Driven Catalysis

Localized surface plasmon resonance has been demonstrated to provide effective photophysical enhancement mechanisms in plasmonic photocatalysis.However,it remains highly challenging for distinct mechanisms to function in synergy for a collective gain in catalysis due to the lack of spatiotemporal control of their effect.Herein,the anisotropic plasmon resonance nature of Au nanorods was exploited to achieve distinct functionality towards synergistic photocatalysis.Photothermal and photochemical effects were enabled by the longitudinal and transverse plasmon resonance modes,respectively,and were enhanced by partial coating of silica nanoshells and epitaxial growth of a reactor component.Resonant excitation leads to a synergistic gain in photothermal-mediated hot carrier-driven hydrogen evolution catalysis.Our approach provides important design principles for plasmonic photocatalysts in achieving spatiotemporal modulation of distinct photophysical enhancement mechanisms.It also effectively broadens the sunlight response range and increases the efficacy of distinct plasmonic enhancement pathways towards solar energy harvesting and conversion.

Effect of electron injection in copper-contacted graphene nanoribbons

For practical electronic device applications of graphene nanoribbons (GNRs), it is essential to have abrupt and well-defined contacts between the ribbon and the adjacent metal lead. By analogy with graphene, these contacts can induce electron or hole doping, which may significantly affect the I/V characteristics of the device. Cu is among the most popular metals of choice for contact materials. In this study, we investigate the effect of in situ intercalation of Cu on the electronic structure of atomically precise, spatially aligned armchair GNRs of width N = 7 (7-AGNRs) fabricated via a bottom-up method on the Au(788) surface. Scanning tunneling microscopy data reveal that the complete intercalation of about one monolayer of Cu under 7-AGNRs can be facilitated by gentle annealing of the sample at 80 °C. Angle-resolved photoemission spectroscopy (ARPES) data clearly reflect the one-dimensional character of the 7-AGNR band dispersion before and after intercalation. Moreover, ARPES and core-level photoemission results show that intercalation of Cu leads to significant electron injection into the nanoribbons, which causes a pronounced downshift of the valence and conduction bands of the GNR with respect to the Fermi energy (ΔE ~ 0.5 eV). As demonstrated by ARPES and X-ray absorption spectroscopy measurements, the effect of Cu intercalation is restricted to n-doping only, without considerable modification of the band structure of the GNRs. Post-annealing of the 7-AGNRs/Cu/Au(788) system at 200 °C activates the diffusion of Cu into Au and the formation of a Cu-rich surface Au layer. Alloying of intercalated Cu leads to the recovery of the initial position of GNR-related bands with respect to the Fermi energy (E F), thus, proving the tunability of the induced n-doping.

High-Consistency Behavior Modeling of a Switched-Capacitor Sigma-Delta Modulator in SIMULINK

To improve the simulation accuracy of SIMULINK, a novel inclusive behavior model of an integrator is proposed that introduces the effects of different circuit nonidealities of a switched-capacitor sigma-delta modulator into SIMULIK simulation. The nonlinear DC gain and nonlinear settling process are introduced into the op-amp module. The signaldependent charge injection and nonlinear resistance are introduced into the switch module. In addition, the noise source including flicker and thermal noise is introduced into system as an independent module. The novel model is verified by SIMULINK behavioral simulations. The results are compared with results from circuit level simulation in Cadence SPICE using TSMC 0.35μm mixed signal technology. It shows that the novel model succeeds in introducing the influences of the nonidealities into behavior simulation to more realistically describe the circuit performances and increase the accuracy of SIMULINK simulation.

Investigation of top-emitting OLEDs using molybdenum oxide as anode buffer layer

A high-effective bottom anode is essential for high-performance top-emitting organic light-emitting devices (OLEDs). In this paper, Ag-based top-emitting OLEDs are investigated. Ag has the highest reflectivity for visible light among all metals, yet its hole-injection properties are not ideal for anodes of top-emitting OLED. The performance of the devices is significantly improved using the molybdenum oxide as anode buffer layer at the surface of Ag. By introducing the molybdenum oxide, the hole injection from Ag anodes into top-emitting OLED is largely enhanced with rather high reflectivity retained.

A 10-bit 100-Msps low power time-interleaved ADC using OTA sharing

A high performance 10-bit 100-MS/s two-channel time-interleaved pipelined ADC is designed for intermediate frequency 3G receivers,and OTA is shared among the channels for low power dissipation.Offset mismatch, gain mismatch and time skew mismatch are overcome by OTA sharing,increasing the accuracy of each channel and global passive sampling respectively.The linearity deterioration caused by the charge injection of the output switch and the crosstalk of the off-switch capacitor is removed by modifying the clock signal arrangement.The total power consumption of the presented ADC is 70 mW from a 3.3-V power supply.Fabricated in a 180-nm CMOS process,the core of the prototype occupies an area of 2.5×1.5 mm;,achieving more than 70-dB spurious-free dynamic range and over 56-dB signal-to-noise distortion ratio over the Nyquist input band at 100-MHz sampling frequency.

ZnO Surface Passivation with Glucose Enables Simultaneously Improving Efficiency and Stability of Inverted Polymer:Non-fullerene Solar Cells

The power conversion efficiency(PCE)of polymer solar cells(PSCs)has exceeded 19%due to the rapid progress of photoactive organic materials,including conjugated polymer donors and the matched non-fullerene acceptors(NFAs).Due to the high density of oxygen vacancies and the consequent photocatalytic reactivity of ZnO,structure inverted polymer solar cells with the ZnO electron transport layer(ETL)usually suffer poor device photostability.In this work,the eco-friendly glucose(Glu)is found to simultaneously improve the efficiency and stability of polymer:NFA solar cells.Under the optimal conditions,we achieved improved PCEs from 14.77%to 15.86%for the PM6:Y6 solar cells.Such a PCE improvement was attributed to the improvement in J_(SC) and FF,which is ascribed to the smoother and more hydrophobic surface of the ZnO/Glu surface,thereby enhancing the charge extraction efficiency and inhibiting charge recombination.Besides,UV-Vis absorption spectra analysis revealed that glucose modification could significantly inhibit the photodegradation of Y6,resulting in a significant improvement in the stability of the device with 92%of its initial PCE after aging for 1250 h.The application of natural interface materials in this work brings hope for the commercial application of organic solar cells and provides new ideas for developing new interface materials.

A novel 2.2 Gbps LVDS driver circuit design based on 0.35μm CMOS

This paper presents a novel high-speed low voltage differential signaling （LVDS） driver design for pointto-point communication. The switching noise of the driver was greatly suppressed by adding a charge/discharge circuit and the operating frequency of the circuit was also increased. A simple and effective common-mode feedback circuit was added to stabilize the output common-mode voltage. The proposed driver was implemented in a standard 0.35 μm CMOS process with a die area of 0.15 mm^2. The test result shows that the proposed driver works well at 2.2 Gbps with power consumption of only 23 mW and 21.35 ps peak-to-peak jitter under a 1.8 V power supply.

In-Vitro and In-Vivo Electrical Characteristics of a Penetrating Microelectrode Array for Optic Nerve Electrical Stimulation

The Chinese C-Sight team aims to restore vision to blind patients by means of stimulating the optic nerve with a penetrating microelectrode array. A biocompatible, implantable microwire array was developed having four platinum-iridium shafts, each 100μm in diameter. This penetrating microwire array is described in this paper, including its fabrication techniques and its in-vitro electrical characteristics. Every set of four shafts was spaced 0.4mm from center to center, comprising two short shafts that were 0.3mm long and two that were 0.9mm long. This design was intended to stimulate ganglion cell axons at different depths within the optic nerve. In-vitro electrochemical impedance testing results showed that the impedance at 1kHz ranged from 8 to 10kΩ at room temperature. The voltage responses of the arrays to current pulse stimulation indicated a charge-injection capacity of 210μC/cm2. Finally, in-vivo acute animal experiments showed that the amplitude of the electrically evoked potentials (EEPs) measured in primary visual cortex could be as large as 100 μV upon direct stimulation of the optic nerve.