Improved performance of organic light-emitting diodes with dual electron transporting layers

In this study the performance of organic light-emitting diodes （OLEDs） are enhanced significantly, which is based on dual electron transporting layers （13phen/CuPc）. By adjusting the thicknesses of Bphen and CuPc, the maximal luminescence, the maximal current efficiency, and the maximal power efficiency of the device reach 17570 cd/m^2 at 11 V, and 5.39 cd/A and 3.39 lm/W at 3.37 mA/cm^2 respectively, which are enhanced approximately by 33.4%, 39.3%, and 68.9%, respectively, compared with those of the device using Bphen only for an electron transporting layer. These results may provide some valuable references for improving the electron injection and the transportation of OLED.

High-power SiC MESFET using a dual p-buffer layer for an S-band power amplifier

A silicon carbide （SIC） based metal semiconductor field effect transistor （MESFET） is fabricated by using a standard SiC MESFET structure with the application of a dual p-buffer layer and a multi-recessed gate to the process for an S-band power amplifier. The lower doped upper-buffer layer serves to maintain the channel current, while the higher doped lowerbuffer layer is used to provide excellent electron confinement in the channel layer. A 20-mm gate periphery SiC MESFET biased at a drain voltage of 85 V demonstrates a pulsed wave saturated output power of 94 W, a linear gain of 11.7 dB, and a maximum power added efficiency of 24.3% at 3.4 GHz. These results are improved compared with those of the conventional single p-buffer MESFET fabricated in this work using the same process. A radio-frequency power output greater than 4.7 W/mm is achieved, showing the potential as a high-voltage operation device for high-power solid-state amplifier applications.

Ternary MOF‑Based Redox Active Sites Enabled 3D‑on‑2D Nanoarchitectured Battery‑Type Electrodes for High‑Energy‑Density Supercapatteries

Designing rationally combined metal-organic frameworks(MOFs)with multifunctional nanogeometries is of significant research interest to enable the electrochemical properties in advanced energy storage devices.Herein,we explored a new class of binderfree dual-layered Ni-Co-Mn-based MOFs(NCM-based MOFs)with three-dimensional(3D)-on-2D nanoarchitectures through a polarityinduced solution-phase method for high-performance supercapatteries.The hierarchical NCM-based MOFs having grown on nickel foam exhibit a battery-type charge storage mechanism with superior areal capacity(1311.4μAh cm^−2 at 5 mA cm^−2),good rate capability(61.8%;811.67μAh cm^−2 at 50 mA cm^−2),and an excellent cycling durability.The superior charge storage properties are ascribed to the synergistic features,higher accessible active sites of dual-layered nanogeometries,and exalted redox chemistry of multi metallic guest species,respectively.The bilayered NCM-based MOFs are further employed as a battery-type electrode for the fabrication of supercapattery paradigm with biomass-derived nitrogen/oxygen doped porous carbon as a negative electrode,which demonstrates excellent capacity of 1.6 mAh cm^−2 along with high energy and power densities of 1.21 mWh cm^−2 and 32.49 mW cm^−2,respectively.Following,the MOF-based supercapattery was further assembled with a renewable solar power harvester to use as a self-charging station for various portable electronic applications.

Resource Allocation for Physical Layer Security in Heterogeneous Network with Hidden Eavesdropper

The tremendous performance gain of heterogeneous networks(Het Nets) is at the cost of complicated resource allocation. Considering information security, the resource allocation for Het Nets becomes much more challenging and this is the focus of this paper. In this paper, the eavesdropper is hidden from the macro base stations. To relax the unpractical assumption on the channel state information on eavesdropper, a localization based algorithm is first given. Then a joint resource allocation algorithm is proposed in our work, which simultaneously considers physical layer security, cross-tier interference and joint optimization of power and subcarriers under fairness requirements. It is revealed in our work that the considered optimization problem can be efficiently solved relying on convex optimization theory and the Lagrangian dual decomposition method is exploited to solve the considered problem effectively. Moreover, in each iteration the closed-form optimal resource allocation solutions can be obtained based on the Karush-Kuhn-Tucker(KKT) conditions. Finally, the simulation results are given to show the performance advantages of the proposed algorithm.

2D–3D dual carbon layer confined ultrasmall VN nanoparticles for improving lithium-ion storage in hybrid capacitors

Lithium-ion capacitors(LICs) of achieving high power and energy density have garnered significant attention. However, the kinetics unbalance between anode and cathode can impede the application of LICs. Vanadium nitride(VN) with a high theoretical specific capacity(~ 1200 m Ah·g^(-1)) is a better pseudocapacitive anode to match the response of cathode in LICs. However, the insertion/extraction of Li-ions in VN's operation results in significant volume expansion. Herein, the VN/N-r GO-5composite that three-dimentional(3D) dicyandiamidederived-carbon(DDC) tightly wrapped VN quantum dots(VN QDTs) on two-dimentional(2D) reduced graphene oxid(r GO) was prepared by a facile strategy. The VN QDTs can reduce ion diffusion length and improve charge transfer kinetics. The 2D r GO as a template provides support for nanoparticle dispersion and improves electrical conductivity. The 3D DDC tightly encapsulated with VN QDTs mitigates agglomeration of VN particles as well as volume expansion. Correspondingly, the LICs with VN/Nr GO-5 composite as anode and activated carbon(AC) as cathode were fabricated, which exhibits a high energy density and power density. Such strategy provides a perspective for improving the electrochemical properties of LIC anode materials by suppressing volume expansion and enhancing conductivity.

Boundary layer flow over a moving surface in a nanofluid with suction or injection

An analysis is performed to study the heat transfer characteristics of steady two-dimensional boundary layer flow past a moving permeable flat plate in a nanofluid. The effects of uniform suction and injection on the flow field and heat transfer characteristics are numerically studied by using an implicit finite difference method. It is found that dual solutions exist when the plate and the free stream move in the opposite directions. The results indicate that suction delays the boundary layer separation, while injection accelerates it.

Superhydrophobic conductive rubber band with synergistic dual conductive layer for wide-range sensitive strain sensor

Wearable electronic devices have received increasing interests because of their excellent flexibility,stretchability,and human friendliness.As the core components,flexible strain sensors integrated with wide working range,high sensitivity,and environment stability,especially in moisture or corrosive environments,remain a huge challenge.Herein,synergistic carbon nanotubes(CNTs)/reduced graphene oxide(rGO)dual conductive layer decorated elastic rubber band(RB)was successfully developed and treated with hydrophobic fumed silica(Hf-SiO_(2))for preparing superhydrophobic strain sensor.As expected,stable entangled CNTs layer and ultrasensitive microcracked rGO layer endow the sensor with extremely low detection limit(0.1%),high sensitivity(gauge factor is 685.3 at 482%strain),wide workable strain range(0–482%),fast response/recovery(200 ms/200 ms)and favorable reliability and reproducibility over 1000 cycles.Besides,the constructed Hf-SiO_(2) coating also makes the sensor exhibit excellent superhydrophobicity,self-cleaning property,and corrosion-resistance.As a proof of concept,our prepared high-performance strain sensor can realize the full-range monitoring of human motions and physiological signals even in the water environment,including pulse,vocalization,joint bending,running,and gesture recognition.Interestingly,it can also be knitted into a tactile electronic textile for spatial pressure distribution measurement.Thus,this study provides a universal technique for the preparation of high-performance strain sensors with great potential applications in the field of next-generation intelligent wearable electronics.

Improved interfacial and electrical properties of Ge MOS devices with ZrON/GeON dual passivation layer

The interracial and electrical characteristics of Ge metal-oxide-semiconductor （MOS） devices with a dual passivation layer of ZrON/GeON formed by NH3- or N2-plasma treatment are investigated. The experimental results show that the NH3-plasma treated sample exhibits significantly improved interfacial and electrical properties as compared to the samples with N2-plasma treatment and no treatment： a lower interface-state density at the midgap （1.64 × 1011 cm-2, eV- 1） and gate leakage current （9.32 × 10-5 A/cm2 at Vfb ＋ 1 V）, a small capacitance equivalent thickness （1.11nm） and a high k value （32）. X-ray photoelectron spectroscopy is used to analyze the involved mechanisms. It is indicated that more GeON and less GeOx （x 〈 2） are formed on the Ge surface during NH3-plasma treatment than the NE-plasma treatment, resulting in a high-quality high-k/Ge interface, because H atoms and NH radicals in NHa-plasma can enhance volatilization of the unstable low-k GeOx, creating high-quality GeON passivation layer. Moreover, more nitrogen incorporation in ZrON/GeON induced by NHa-plasma treatment can build a stronger N barrier and thus more effectively inhibit in-diffusion of O and Ti from high-k gate dielectric and out-diffusion of Ge.