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The manufacture of bipolar junctions is necessary in many 4H-SiC electronic devices, e.g., junction termination extensions and p + in diodes for voltage class > --> 10 kV. However, the presence of electrically active levels in the drift layer that act as minority charge carrier lifetime killers, like the carbon vacancy (V C), undermines device performance. In the present study, we compared p + n diodes whose anodes have been manufactured by three different methods: by epitaxial growth, ion implantation, or plasma immersion ion implantation (PIII). The identification of the electrically active defects in the drift layers of these devices revealed that a substantial concentration of V C is present in the diodes with epitaxial grown or ion implanted anode. On the other hand, no presence of V C could be detected when the anode is formed by PIII and this is attributed to the effects of strain in the anode region. Our investigation shows that PIII can be a useful technique for the manufacture of bipolar devices with a reduced concentration of lifetime killer defects. [ABSTRACT FROM AUTHOR]

We report the design, fabrication, and measurement of the field emission (FE) characteristics of AlGaN/GaN nanoscale lateral vacuum diodes with triangular cathodes and cathode to anode spacings from 50 to 600 nm. The FE characteristics of the AlGaN/GaN diodes with metallic or AlGaN/GaN anodes show successful rectification with forward bias FE current in the range of microamperes or milliamperes, respectively, when biased within a maximum range varying from 10 to 30 V. In the forward bias mode, the measured current I m vs applied anode to cathode bias V m are well fitted to Murphy–Good profiles associated with FE at higher biases, and an Ohmic leakage profile below the threshold for FE. Our results are the first successful demonstration of FE of electrons between the two two-dimensional electron gases (2DEGs) present on both sides of a nanogap formed by electron lithography through an AlGaN/GaN heterojunction. A qualitative explanation of the loop-type FE characteristics of both AlGaN/GaN vacuum diodes, with either metallic or AlGaN/GaN anodes, is presented. [ABSTRACT FROM AUTHOR]

Dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) is a widely used small-molecular p-type organic semiconductor. Despite the broad availability of high-performance DNTT transistors, there is a lack of investigation into other devices based on this semiconductor. In this study, rectifying diodes with DNTT as a single transport medium are fabricated and characterized. Realizing unipolar current rectification from asymmetric metal contacts, a number of physical and electrical properties of DNTT are made accessible. Current–voltage measurement, broad-band impedance spectroscopy, drift-diffusion simulation, and equivalent-circuit modeling are combined to quantify important parameters such as dielectric constant, trap energy, and lifetime. These results provide a practical reference for the design and optimization of diverse electronic devices incorporating DNTT. [ABSTRACT FROM AUTHOR]

A practical quantitative model is presented to account for the I–V characteristics of pin diodes based on epitaxial Ge-like materials. The model can be used to quantify how the different material properties and recombination mechanisms affect the diode performance. The importance of dislocations, non-passivated defects, and residual intrinsic layer doping in determining the qualitative shape of the I–V curves is discussed in detail. Examples are shown covering literature diodes as well as diodes fabricated with the purpose of validating the theoretical effort. [ABSTRACT FROM AUTHOR]

β-Ga2O3 is of great interest for power electronic devices with efficiency beyond current generation Si, 4H-SiC, and GaN devices due to its large breakdown electric field of ∼8 MV/cm. However, taking advantage of this large field strength in power diodes requires device engineering to reduce leakage current that arises at high electric fields. In this work, we elucidate the current transport mechanisms of metal/TiO2/β-Ga2O3 diodes, showing that thermionic emission is an excellent descriptor of current in forward and reverse bias. It is shown that tunneling current is greatly suppressed, and consequently, that the diodes with the TiO2 interlayer can block orders of magnitude more current than Schottky barrier diodes with the same barrier heights. Finally, a 1200 V diode structure is designed based on the derived transport models, and calculated on- and off-state current characteristics closely align with those of state-of-the-art 4H-SiC commercial devices, indicating that this diode structure is ready to enable the realization of β-Ga2O3 power diodes. [ABSTRACT FROM AUTHOR]

The small-signal equivalent circuit of GaN-based self-switching diodes has been obtained, which apart from the intrinsic R ‖ C branch, generally used to describe the diode performance, needs new elements to describe the low-frequency dispersion of the impedance originated by the presence of surface and bulk traps. The proposed model allows us to reproduce not only the high-frequency results (extracted from S-parameter measurements in the 40 MHz–43.5 GHz range) at room temperature, but also the low-frequency impedance measurements (75 kHz–30 MHz) at cryogenic temperatures down to 70 K. These new elements are a self-inductance associated to the effect of surface states (typical of a device with a high surface-to-volume ratio) and an extra series R – C branch modeling the influence of the bulk traps. [ABSTRACT FROM AUTHOR]

Electronics today has evolved significantly, including its application in transparent and flexible devices. Flexible electronics offers new product concepts, including low production cost, low energy consumption, and sustainable and environmentally friendly materials. This concept leads to the development of novel materials that realize today's requirements. Incorporating optically transparent and flexible thin-film-based devices into the electronic circuitry helps in maintaining high conductivity along with achieving the similar electronic behavior of the conventional electronic gadgets. Thin-film diodes (TFDs) and thin-film transistors (TFTs) are the core materials to be incorporated as building blocks for flexible devices. Among them, oxide-based thin films have been marked to be significant because of their efficient electrical performance, low temperature processing, and device flexibility. The present article reviews the concepts and application of zinc oxide (ZnO) as the semiconducting material for flexible thin-film devices. We also review flexible and transparent TFDs and TFTs that are based prominently on ZnO as the semiconducting material. Furthermore, the present issues have also been addressed. [ABSTRACT FROM AUTHOR]

This paper presents a novel physics-based analytical model for the injection recombination current in micro-light emitting diodes (μLEDs) with multiple quantum wells (MQWs), specifically excluding trap-assisted tunneling contributions at low forward voltages. The model simplifies the complex MQW structure by representing MQWs as a single equivalent quantum well (EQW). The μLED current is attributed to the recombination of injected holes and electrons within this EQW. Key parameters of the model encompass the EQW's position within the depletion region, hole diffusion coefficient, series resistance, and thermal resistance of the device. Experimental validation of the model is performed using current–voltage characteristics obtained from InGaN/GaN QW μLEDs. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions are nanoscale spin textures with topological protection properties, which are regarded as promising information carriers. When skyrmions move along nanotracks, their trajectories will shift if affected by skyrmion Hall effect and pinning effect. In this work, the influence of trapezoidal notches in synthetic antiferromagnetic nanotracks on the dynamics of skyrmions is investigated through micromagnetic simulation. The results exhibit that the asymmetric energy barrier induced by the asymmetric geometric structure can hinder reverse motion of skyrmions to realize the unidirectional conduction function of the diodes. Adjusting the height and inclination angle of the trapezoidal notch can effectively expand the current operating windows of the diodes, and the larger the height or inclination angle, the higher the threshold current density to overcome the pinning effect of the geometric energy barrier. Furthermore, the failure mode has a crucial impact on the implementation of skyrmion diodes. By utilizing the asymmetric structure, the forward conduction and reverse cutoff of skyrmion-based diodes can be achieved within 4 ns, with lower energy consumption than traditional diodes, resulting in high efficiency and low energy consumption of diodes. This work proposes a method for realizing the diode functionality by simply altering the geometric structure of the nanotracks, which may play an important role in the design and application of skyrmion-based diodes. [ABSTRACT FROM AUTHOR]

This work focuses on the electrical transport and conduction mechanisms — inside a sprayed — made zinc oxide-on-p-type silicon junction device. A fabricated Al/ZnO/Si/Al heterojunction is characterized at 300 and 380 K in the dark. The aforementioned theories predict that the current density (J) is an exponential function of measured voltage (V) and work temperature (T). Exponential equations are linearized as a result of a current conduction mechanism (CCM) kind. Useful parameters like barrier height φ t of trap are extracted from the slope B. Ohmic and space charge limited current (SCLC) regimes inside are studied at 300 and 380 K recording a shift in exponent as a result of temperature. Fowler–Nordheim (FN) conduction mechanism inside Al/ZnO/Si/Al device is considered slope and ϕ b values are determined for two cited work temperatures. Our device presents a thermionic emission (TE) and exhibits an effect of temperature on slope and intercept values of (ln J T E /A* T 2 ) function. The Poole–Frenkel (PF) emission in terms of 1/V data are presented for 300 and 380 K. Besides, PF emission mechanism in terms of 1/ T 2 is exhibited and parameters are influenced by temperature. Behavior of conductance as a result of temperature is detailed and evidenced. [ABSTRACT FROM AUTHOR]

Multilevel inverters produce waveforms that lead to better power quality. Switched-capacitor inverters are one kind that is capable of generating boosted voltage and encourages a single-stage grid-tied inverter solution. In this paper, a four-times boost nine-level inverter with fewer switches is presented in standalone and grid-connected mode. Two switched capacitors, along with eleven switches and one diode, are employed to generate the required boosted nine-level output. The circuit modulation allows self-charging of the capacitors, with the first capacitor charging to the DC source and the second charges to twice of it by shunting it with the combination of the first capacitor voltage and the DC source. This inverter's application can be as a solar PV microinverter due to its fewer components and small filter requirement. The topology is compared with the single-source nine-level inverters and exhibits the lowest cost of all quadruple boost inverters. The presented inverter operation is verified in Simulink and validated on the laboratory prototype. Further, to minimize the leakage current, the circuit is modified accordingly and tested in a hardware-in-the-loop environment. [ABSTRACT FROM AUTHOR]

In this study, three stable tetradentate Pt(II) complexes are synthesized and characterized, namely, Pt‐biPh, Pt‐biPh5tBu, and Pt‐biPh4tBu, tailored for blue phosphorescent organic light‐emitting diodes to realize high‐efficiency and narrowband emissions via ligand engineering. Biphenyl (Pt‐biPh) or tert‐butyl‐modified biphenyl (Pt‐biPh5tBu and Pt‐biPh4tBu) is introduced into the carbene unit of the ligand to control the intermolecular interactions between the Pt(II) phosphors. Pt‐biPh, Pt‐biPh5tBu, and Pt‐biPh4tBu exhibit high photoluminescence quantum yields of 74%, 84%, and 92% with exciton lifetimes of 2.2, 2.3, and 2.5 µs, respectively, demonstrating rapid and efficient light emission. Furthermore, Pt‐biPh, Pt‐biPh5tBu, and Pt‐biPh4tBu show maximum external quantum efficiency (EQE) values of 18.1%, 19.0%, and 21.8%, respectively. Pt‐biPh5tBu and Pt‐biPh4tBu exhibit narrowband emission with a full width at half maximum of 21 nm owing to the small vibrational emission because of their sterically hindered and bulky ligand structures. Moreover, phosphor‐sensitized thermally activated delayed fluorescence devices employing a Pt‐biPh4tBu sensitizer achieve a high EQE of 28.6%. In particular, Pt‐biPh4tBu performs better than the state‐of‐the‐art phosphor as the sensitizer of the blue phosphor‐sensitized thermally activated delayed fluorescence devices in terms of the EQE. [ABSTRACT FROM AUTHOR]

This paper introduces a coupled inductor (CI)‐based high step‐up DC‐DC converter. Cascaded or quadratic DC–DC converters are the most practical solution to achieve a wide conversion ratio and reduced current ripple. The proposed structure (P1) is achieved by a combination of a base structure of two‐stage boost converter with one active switch, a CI, and a voltage multiplier cell (VMC). The secondary side of the CI is placed at the output side, where it is combined with a VMC. In the proposed topology, a passive clamp consisting of a diode and a capacitor is added to minimize the voltage stress on the active switch. In addition, the passive clamp recycles the leakage energy of the CI and causes to increase the efficiency. The input source current ripple is low, and the input current is continuous, which are very suitable for renewable energy applications. Additionally, the voltage stresses on switches are less than some quadratic DC‐DC boost converters that have been presented. Also, an extended topology of P1 is proposed as the second proposed converter (P2), to enhance the operation of P1. Moreover, to show the feasibility and performance of the presented converter, a laboratory prototype circuit is examined. The results accredit the theoretical analysis and experimental outcomes of the presented converter. [ABSTRACT FROM AUTHOR]

A new gate driver with metal oxide thin‐film transistors (MO‐TFTs) has been presented for micro‐light‐emitting diode (Micro‐LED) display. The proposed gate driver employing linearly decreasing sweep signal generated module could realize the line‐by‐line pulse width modulation (PWM) driving method, which is valuable for application in high‐resolution Micro‐LED display compared with the conventional driving method employing global sweep signal. A simple Micro‐LED pixel circuit including an inverter module driven by the analog PWM method is employed to demonstrate the feasibility of the proposed gate driver. A 10 × 10 green Micro‐LED display array has been fabricated with MO‐TFTs backplane technology. It is shown that a 10‐μs width pulse and linearly scanning sweep signal can be successfully output. Consequently, the pixel circuit array can be driven properly under analog line‐by‐line PWM driving method. [ABSTRACT FROM AUTHOR]

The axial gap structure of a half‐wave rectified variable field flux motor (AG‐HVFM) has been proposed, which has a double stator structure and field winding short‐circuited by a diode. Although the AG‐HVFM can achieve a high‐efficiency drive in wide speed and torque range via variable field flux control, its structure deteriorates the average torque and torque ripple. In this paper, we sequentially design the core shape, aspect ratio, and current control method for an AG‐HVFM to improve its torque characteristics. [ABSTRACT FROM AUTHOR]

Summary: This paper suggests an extendable voltage boosting gain unit (EVBGU) using switched‐capacitors SC with a single DC source. The proposed unit can be extended by a modular pattern to increase the output voltage levels and voltage‐boosting gain of the inverter. The main feature of this work is presenting a unit topology that utilizes multiple and modular subcells to achieve (double, quadruple, hexapole, octapule, etc.) voltage gain at the output by increasing the number of the subcells. All the subcells are connected only with one DC source. A positive feedback technique has been used to charge the capacitors of the unit using the accumulative charging voltage (ACV) method. Furthermore, all the capacitors are self‐balanced, so there is no need for any additional and complex control circuit. Moreover, to decrease the cost factor of the inverter, a low IGBT switch count is taken into consideration and no passive elements such as diodes are used in the proposed structure. The H‐bridge is connected to the unit to achieve bipolar voltage at the output. The operational analysis of the inverter is delineated in detail. A comparative study, with state‐of‐the‐art MLIs in different terms such as the number of components, the total standing voltage, and the gain, shows the particularity of the proposed EVBGU. The simulation of the proposed MLI is performed using PSCAD‐EMTDC software. The simulation results are validated experimentally. [ABSTRACT FROM AUTHOR]

Switching of vertical 6.1 kV/4A NiO/Ga2O3 rectifiers from voltages up to 1.45 kV showed reverse recovery times of 75 ns, current slew rate of 39.0 A/μs, and energy loss of ∼105 μW. These are the highest switching voltages reported for Ga2O3 rectifiers. To place the results in context, commercial 3.3 kV/5 A SiC merged PiN Schottky diodes showed reverse recovery times of 20 ns, current slew rate of 47.5 A/μs, and energy loss of ∼67 μW. The validity of comparing unpackaged experimental Ga2O3 diodes with commercial Si or SiC diodes without considering their differences in chip size and consequently in capacitive charge and ON-resistance is restricted. However, the results show the rapid progress in these devices when compared to commercial SiC rectifiers. [ABSTRACT FROM AUTHOR]

This paper presents a design and analysis of novel DC-DC boost converter with a least component count. The proposed converter produces high DC gain voltage in comparison to some recently presented high voltage DC-DC converter. Here one switch, one inductor, two capacitors and one diode are used to achieved a high voltage gain without compromising efficiency of converter. The converter’s performance is evaluated using theatrical, simulation and experimental methods, with results indicating a four times of input voltage and a fast-transient response at various duty cycles is achieved. Due to its low component count the proposed converter is compact and hence it offers an effective solution for various power applications. [ABSTRACT FROM AUTHOR]

Multiresonance thermally activated delayed fluorescence (MR‐TADF) emitters with high color purity in virtue of their inherent narrowband emission have received great interest in organic light‐emitting diodes (OLEDs). However, it remains a big challenge to develop the ultrapure blue MR‐TADF emitters with high efficiency. In this work, a novel “dual‐MR‐core” strategy is proposed by connecting two parent N‐B‐O‐skeletons with non‐conjugate 9‐position substituted fluorene linkages for high efficient deep‐blue MR‐TADF emitters, namely H‐FOBN and Me‐FOBN, which possess the highly twisted structure with suppressed aggregation. Finally, the vacuum‐deposited deep‐blue OLED exhibits excellent external quantum efficiency (EQE) of 25.1% with small full width at half maximum (FWHM) of 28 nm, as well as CIE of (0.14, 0.08). Furthermore, owing to enhanced solubility, the solution‐processed deep‐blue OLED based on Me‐FOBN shows EQE of 11.3%, with small FWHM of 32 nm and CIE of (0.14,0.09). These outstanding performances confirm that this “dual‐MR‐core” strategy provides a feasible approach to develop high efficient ultrapure blue MR‐TADF emitters. [ABSTRACT FROM AUTHOR]

Hybride white organic light‐emitting diodes (WOLEDs) have experienced great success as a prospective technology for the new generation lighting source. Nevertheless, WOLEDs exhibiting excellent effciency and good color stability at high operation brightness are still rare. Herein, a simple but efficient blue molecule, pyrenoimidazole‐biphenyl (PPyIM), which exhibits promising external quantum efficiency (EQE) of 7.6% and 7.2% at the luminescence of 1000 −and 5000 cd m−2 in nondoped blue OLED, is first developed. And then, phenanthroimidazole‐biphenyl (PPIM) with analogous molecular skeleton of PPyIM is chosen as the host of phosphorescent dye PO‐01, and the resulting doped device achieves excellent EQE of 26.5% at the high luminescence of 5000 cd m−2. Furthermore, adopting PPyIM as nondoped blue emissive layer, the two‐color hybrid WOLED exhibites stable warm white emission with CIE coordinates of (0.454, 0.439), color rendering index (CRI) of 45, and correlated color temperature (CCT) of 2996 K. The maximum EQE reaches 23.5%, and the EQE still maintains 21.2% even at the luminance of 5000 cd m−2. Notably, this device exhibits exceptionally stable warm white emission, the CIE coordinates variation is only (0.004, 0.003) in the wide luminance range from 400 to 10000 cd m−2, representing the best outcome for hybrid WOLEDs to date. [ABSTRACT FROM AUTHOR]

In this study, we propose a novel p‐i‐n AlGaN electron‐blocking layer for GaN‐based LEDs. The aim is to enhance the confinement of electrons and improve the efficiency of hole injection, ultimately resulting in a significant enhancement in LED performance. Detailed simulations and analysis were conducted to compare the performances of GaN‐based LEDs with a conventional EBL and our proposed EBL. It was observed that our newly proposed p‐i‐n AlGaN EBL significantly outperforms the conventional EBL in terms of output power and efficiency across a wide range of injecting currents. These improvements can be attributed to the strong reverse electrostatic field induced by our proposed p‐i‐n AlGaN EBL, which not only enhances electron confinement but also improves hole injection efficiency. [ABSTRACT FROM AUTHOR]

This paper details the fabrication of GaN-based microdisks with a single porous n-GaN layer positioned beneath the multiple quantum wells region on a modified green light-emitting diode epiwafer. Simulations of the longitudinal light field distribution reveal effective confinement of the light field within the multiple quantum wells region due to the presence of the single porous layer. The porous layer also demonstrates sufficient conductivity as determined through calculations and serves as an effective method for thermal dispersion. Under optical pumping, all microdisks exhibit clear whispering gallery mode (WGM) lasing at room temperature, with the lowest threshold of 13.50 μJ/cm2 achieved in a 2-μm-diameter microdisk. These findings suggest that integrating the single porous layer into GaN microdisks is a highly promising approach for achieving high-efficiency WGM micro-laser diodes with effective electrical injection and heat dispersion. [ABSTRACT FROM AUTHOR]

ABSTRACT Two new full‐wave rectifiers (FWRs) based on two plus‐type second‐generation current conveyors are proposed in this paper. Also, the proposed FWR structures comprise two diodes and two grounded resistors without matching conditions. They are not affected from any bias voltage(s) and/or current(s); thus, they eliminate the need for extra circuitry. One of the proposed FWRs provides positive rectification, while the other offers negative rectification. Both proposed FWRs have high input impedance and gain. Simulation results are obtained through the SPICE program, and experimental results are provided. [ABSTRACT FROM AUTHOR]

This brief proposes an improved pulse width modulation (PWM) scheme, which uses diode voltage clamping characteristics to achieve the direct control of three‐phase current source converter without any logical transformation. Compared with the traditional indirect carrier modulation scheme—mapping‐PWM, the proposed scheme can solve the disadvantages of low DC current utilization, high switching loss, and complex control process. The generation mechanism of IPWM is analyzed in this brief. Then, based on the generation mechanism, the output characteristics of the system under IPWM are analyzed and compared with the traditional modulation scheme. Finally, the experimental results verify the effectiveness the proposed modulation scheme. [ABSTRACT FROM AUTHOR]

Far‐red (FR) and near‐infrared (NIR) spectroscopy technologies have attracted extensive attention. How to obtain luminescent materials suitable to FR‐NIR phosphor‐converted light‐emitting diodes (pc‐LEDs) is a crucial challenge. Herein, a Si3N4‐substitution strategy is employed to regulate the luminescence of Gd3Ga5O12:Cr3+ (GGG:Cr3+) phosphors. The bandwidth of GGG:Cr3+ is 95 nm, and then it is broadened to 116 nm due to the Si3N4‐substitution. Furthermore, at 423 K the thermal stability is enhanced to 98.7% of that at room temperature, which is higher than the reported 92.7%@423 K for the Si3N4‐free sample. The intensity of the optimal specimen is elevated 2.9 times compared with the Si3N4‐free sample sintered at the same condition. The FR pc‐LED is manufactured by using the optimized sample, and its FR output power is 47.1 mW with a conversion efficiency of 15.9% driven by 100 mA. This work paves a new way to design high‐performance NIR phosphors. [ABSTRACT FROM AUTHOR]

Ferroelectricity, band topology, and superconductivity are respectively local, global, and macroscopic properties of quantum materials, and understanding their mutual couplings offers unique opportunities for exploring rich physics and enhanced functionalities. In this mini‐review, the attempt is to highlight some of the latest advances in this vibrant area, focusing in particular on ferroelectricity‐tuned superconductivity and band topology in 2D materials and related heterostructures. First, results from predictive studies of the delicate couplings between ferroelectricity and topology or superconductivity based on first‐principles calculations and phenomenological modeling are presented, with ferroelectricity‐enabled topological superconductivity as an appealing objective. Next, the latest advances on experimental studies of ferroelectricity‐tuned superconductivity based on different 2D materials or van der Waals heterostructures are covered. Finally, as perspectives, schemes are outlined that may allow to materialize new types of 2D systems that simultaneously harbor ferroelectricity and superconductivity, or that may lead to enhanced ferroelectric superconductivity, ferroelectric topological superconductivity, and new types of superconducting devices such as superconducting diodes. [ABSTRACT FROM AUTHOR]

A DC‐DC converter with high boost and low switching voltage stress is proposed by combining switched capacitor (SC) and coupled inductor (CL) techniques based on a conventional boost circuit. The design methodology of this converter includes substituting SC for a single switch in the boost converter, combining CL, and integrating a resonant boost circuit for absorbing leakage inductance. The improved power switch topology in this design has lower voltage stress, lower diode current stress, fewer total components, and common ground than other conventional DC‐DC converters. The operating modes and steady state analysis of the converter are provided in terms of leakage inductance utilization, with component stress derivation and theoretical efficiency analysis. In addition, comparisons with other dc‐dc converters are made. Subsequently, experiments were conducted on a 200 W DC‐DC converter prototype to verify the reliability of the converter. [ABSTRACT FROM AUTHOR]

Although exciplex hosts have been used to enhance the operational lifetime of blue phosphorescent organic light‐emitting diodes, their detailed design rule has not been established because of their unresolved degradation. In this work, the underlying mechanisms involved in device degradation are investigated, focusing on the tailor‐tuning effect of the exciplex host to maximize the device's lifetime with a given phosphorescent dopant. Analysis of trap dynamics shows that the stability improvement caused by adding an electron‐donating unit to the N‐type host does not originate from the stable positive polaron state. It is found that the exciplex host modified with minor substituents opens extra pathways for polaron transport and exciton generation rather than chemical stability, resulting in the spatial dispersion of polarons and excitons. The dispersion of excitons and polarons, in turn, enhances the recombination coefficient and suppresses exciton–exciton and exciton–polaron bimolecular interactions, enabling further improved device stability. With comprehensive analysis, a perspective on the role of the host in the degradation mechanism is presented. [ABSTRACT FROM AUTHOR]

The effect of the active region growth temperature (TMQW) on the external quantum efficiency (EQE) of AlGaN‐based far‐ultraviolet‐C light‐emitting diodes (far‐UVC LEDs) emitting near 235 nm is investigated. AlGaN multi‐quantum well (MQW) active regions are grown at temperatures between 850 and 1100 °C by metal‐organic vapor‐phase epitaxy, while special care is taken to keep aluminum mole fractions and thicknesses constant for all MQWs. Temperature‐ and excitation‐power‐dependent photoluminescence spectroscopy reveal a more than tenfold increase of the radiative recombination efficiency (RRE) when the growth temperature increases from 850 to 1020–1060 °C. The output powers for mounted far‐UVC LEDs at 0.2 A increase from 0.5 mW for TMQW of 900 °C to 2.5 mW for TMQW of 1020 °C, corresponding to an increase in EQE from 0.04% to 0.23% at 0.2 A. However, lifetime measurements reveal a reduction of the L70 lifetime from 400 to 1 h when TMQW increases from 900 to 1060 °C. In this investigation, it is shown that optimizing the growth conditions provides a promising approach to further increase the RRE and EQE and lifetime of far‐UVC LEDs. [ABSTRACT FROM AUTHOR]

Defects in p-type oxide/β-Ga2O3 heterojunction diodes were investigated using p-type Cu2O as a case study. Diodes with polycrystalline and epitaxial Cu2O films were analyzed using deep-level transient spectroscopy. For both diodes, two electron bulk defects were detected, including a minority defect at 0.23 eV below EC within Cu2O and a majority defect at 0.53 eV below EC within β-Ga2O3. Furthermore, a high-density interface state of 4.5 × 1012 cm−2/eV was observed in the polycrystalline Cu2O/β-Ga2O3 diode. The presence of a high density of interface states helped reduce the turn-on voltage owing to the interface recombination current. However, it also enabled electron carriers to tunnel through the interface to β-Ga2O3, followed by variable range hopping through the bulk defect in the β-Ga2O3 layer, ultimately causing undesirable premature breakdown. The results of this study underscore the critical role of optimizing the crystal structure during p-type oxide growth for desired defect characteristics, particularly concerning interface states, in β-Ga2O3 bipolar devices for different applications, offering insights for high-performance power rectifier development. [ABSTRACT FROM AUTHOR]

Improving compactness is essential for high-power microwave (HPM) sources. In this paper, a novel reflective modulation cavity is proposed and investigated in a V-band relativistic coaxial transit-time oscillator (RCTTO). The cold cavity analyses and particle-in-cell simulations show that the reflective modulation cavity has larger reflection coefficients of TEM mode and stronger electron beam modulation capability when compared with a uniform modulation cavity. When the input diode voltage is 391 kV, the beam current is 4.91 kA, and when the guiding magnetic field is 0.6 T, the compact V-band RCTTO produces an output microwave power of 518 MW (conversion efficiency of 27.0%). Compared with the original RCTTO, the compact V-band RCTTO featuring a reflective modulation cavity exhibits a 24.8% increase in output power and a 5.4% improvement in efficiency, and the axial length of the magnetic field uniform region is reduced by 24.2%. The compact V-band RCTTO also demonstrates a broad operation voltage range, indicating potential for stable operation with voltage fluctuations in experiments. Furthermore, the reflective modulation cavity can be integrated into other high-frequency O-type HPM devices to enhance compactness, thereby diminishing the demands on the magnetic field region, which is advantageous for the future permanent packaging of HPM sources. [ABSTRACT FROM AUTHOR]

The series-type 12-pulse rectifier generates a large amount of harmonics in the AC side current due to the strong nonlinearity of its rectifying diodes, causing serious harmonic pollution to the power grid. This article proposes a series 36-pulse rectifier based on a DC side dual passive frequency-doubling circuit to suppress the AC side current harmonics of a 12-pulse rectifier. The rectifier uses two symmetrical passive pulse multiplication circuits to regulate the circulation in the DC side circuit, increasing the output voltage and current state of the rectifier bridge, thereby increasing the number of pulses in the rectifier from 12 times to 36 times. Firstly, the working principle of the rectifier and the working mode of the dual passive frequency-doubling circuit were analyzed. Secondly, the harmonic suppression mechanism of the rectifier input current was revealed, and the frequency-doubling characteristics of the load voltage were analyzed. Finally, the correctness of the theoretical analysis was verified through a semi-physical platform. The verification and comparison results show that under the optimal conditions of the injecting transformer turns ratio, the DPPC can not only reduce the THD value of the input current by about 1/3 (from 14.87% to 4.78%) but can also increase the fluctuation frequency of the load voltage by 3 times (from 12 to 36), while improving the power quality of the AC/DC side rectifier and achieving the low harmonic operation of the rectifier. The proposed 36-pulse rectifier can effectively suppress harmonics; it has the advantages of simple structure, strong robustness, and high output voltage gain, and it is suitable for medium-voltage and high-voltage high-power rectification applications. [ABSTRACT FROM AUTHOR]

Aim Methods Results Conclusion Photopharmacology is a new technique for modulating biological phenomena through the photoconversion of substances in a specific target region at precise times. Caged compounds are thought to be compatible with photopharmacology as uncaged ligands are released and function in a light irradiation‐dependent manner. Here, we investigated whether a microscale light‐emitting diode (MicroLED) probe is applicable for the photoconversion of caged‐glutamate (caged‐Glu) in vivo.A needle‐shaped MicroLED probe was fabricated and inserted into the mouse hippocampal dentate gyrus (DG) with a cannula for drug injection and a recording electrode for measuring the local field potential (LFP). Artificial cerebrospinal fluid (ACSF) or caged‐Glu was infused into the DG and illuminated with light from a MicroLED probe.In the caged‐Glu‐injected DG, the LFP changed in the 10–20 Hz frequency ranges after light illumination, whereas there was no change in the ACSF control condition.The MicroLED probe is applicable for photopharmacological experiments to modulate LFP with caged‐Glu in vivo. [ABSTRACT FROM AUTHOR]

Sulfone group plays a pivotal role in narrowing emission spectra, while, precise modification with sulfone group for carbonyl‐based narrowband emitters that maintain high color purity remains challenging. Herein, a comprehensive exploration of the function of the sulfone group is performed with various sulfur valences and positions fused into traditional carbonyl‐based narrowband emission unit QAO, namely SpiroS‐QAO, SpiroSO2‐QAO, SpiroO‐QAO, and SpiroOSO2‐QAO. A rigid molecular skeleton with a spiro structure as an intramolecular lock enables the four emitters to exhibit narrowband emissions. After full oxidization of sulfur, the emission band of SpiroSO2‐QAO is further narrowed, with full width at half maximum of 32 nm, compared to that of 43 nm for sulfane‐decorated SpiroS‐QAO, which is attributed to the suppressed C─S bond‐length variation by the introduction of sulfone group. Nearly identical spectra of SpiroO‐QAO and SpiroOSO2‐QAO suggest that the sulfone group should be directly linked to the emission core to maximize its function. Maximum external quantum efficiencies of 30.8%, 30.3%, and 29.2% are achieved for SpiroO‐QAO, SpiroOSO2‐QAO, and SpiroS‐QAO‐based sensitized organic light‐emitting diodes with highly efficient thermally activated delayed fluorescence assistant host. These results offer a comprehensive understanding of the sulfone group embedded into the narrowband emission core with respect to the narrowing emission band. [ABSTRACT FROM AUTHOR]

Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials are of vital importance for ultra‐high‐definition displays. However, developing molecular design tactics for blue MR‐TADF emitters that simultaneously achieve good TADF properties, narrowband emission, and ideal molecular orientation remains challenging. Here, an effective approach to enhance the electroluminescent (EL) performance of MR‐TADF emitter by enlarging the molecular planar through a peripheral decoration strategy is presented. The resulting proof‐of‐concept emitter, 3QCzBN, not only exhibits a blue emission with a narrow full‐width at half maximum (FWHM) of only 22 nm, but also a remarkable photoluminescent quantum yield (PLQY) of 98%. Together with the accelerated reverse intersystem crossing (RISC) processes and nearly perfect horizontal ratios of emitting dipole orientation (Θ//) of 98% compared to its parent MR molecule, the organic light‐emitting diodes (OLEDs) based on 3QCzBN demonstrate blue emission with good color purity and an outstanding maximum external quantum efficiency (EQEmax) of 34.8% with low efficiency roll‐off. [ABSTRACT FROM AUTHOR]

This study presents the development of mixed‐ligand quasi‐2D perovskites ((2‐PEA)x(R/S‐2‐BA)2MA1Cs1Pb3Br10+x, x = 0.8, 1.6, 2.4) for circularly polarized light‐emitting diodes (CP‐LEDs). By utilizing the strong confinement effect of 2‐phenylethylammonium (2‐PEA) and the chirality of R/S‐2‐butylammonium (R/S‐2‐BA), room‐temperature circularly polarized luminescence (CPL) across the green to deep blue spectrum is achieved. The green CPL attributes to the transfer of spin‐polarized excitons while the blue CPL originates from direct excitation of luminescent phases with intrinsic chirality. Finally, green and blue CP‐LEDs under ambient are realized. Notably, standard and deep blue CP‐EL is achieved based on 0.8PEA/(R/S‐2‐BA)‐ and 1.2PEA/(R/S‐2‐BA)‐films with impressive electroluminescent asymmetry factors (0.122 and 0.175), highlighting the potential of chiral perovskites in CP‐LEDs and opening avenues for the development of room‐temperature full‐color CP‐EL display. [ABSTRACT FROM AUTHOR]

III–V/III-nitride p–n junctions were realized via crystal heterogeneous integration, and the resulting diodes were characterized to analyze electrical behavior and junction quality. p-type In0.53Ga0.47As, which is a well-established base layer in InP heterojunction bipolar transistor (HBT) technology, was used in combination with a homoepitaxial n-type GaN. The latter offers low dislocation density, coupled with high critical electric field and saturation velocity, which are attractive for use in future HBT collector layers. Transmission electron microscopy confirms an abrupt interface in the fabricated heterogeneous diodes. Electrical characterization of the diodes reveals a near-unity ideality factor (n ∼ 1.07) up to 145 °C, a high rectification ratio of ∼108, and a low interface trap density of 3.7 × 1012 cm−2. [ABSTRACT FROM AUTHOR]

In this paper, a new modular‐isolated‐forward‐based active snubber cell (SC) for power switches is designed. In the proposed new SC, the zero voltage transition (ZVT) technique is implemented with a forward converter although the current counterparts generally use a flyback converter. In the converter with the new SC, the main switch is turned on with ZVT (full zero voltage switching [ZVS]) and turned off with ZVS, the main diode is turned off with zero current switching (ZCS), the auxiliary switch is turned on with ZCS and turned off with ZVS, and the parasitic capacitor energies are recovered. In addition, thanks to the forward converter, it has been possible to minimize the transformer leakage inductance and greatly reduce the current values of devices in the new SC. The new cell is applied to a single‐phase, grid‐connected, T‐type three‐level inverter (T2‐3LI) as an example. A detailed steady‐state analysis of this inverter was made, and the theoretical analysis was confirmed with measurement results taken from a prototype with 100 kHz and 3.3 kW values. Compared to its hard switching (HS) equivalent, in the converter with soft switching (SS) cell, the total circuit loss was reduced from about 248 W to 86 W, thus achieving an increase in the total efficiency from 92.5% to 97.4%. [ABSTRACT FROM AUTHOR]

LLC series resonant converter (LLC‐SRC) has attracted much attention due to its simple circuit structure and easy realization of soft‐switching. To get a better efficiency, rectifier stage can be realized by the active switches instead of the diodes. Meanwhile, more control variables can be selected besides the switching frequency, such as single phase shifted (SPS) angle, dual phase shifted (DPS) angle, and extended phase shifted (EPS) angle. Considering the simplicity of the implementation of the control strategy, this paper focused on the converter model with frequency and SPS control. Different from the common modelling method with the Fundamental Harmonic Approximation (FHA), the precise time‐domain mathematic model is built. By a comparison between the two modelling results, it can be proved the FHA model may be failure in some operating condition while the proposed time‐domain model can still show a good accuracy. According to the proposed model, two simple fixed‐frequency SPS control strategies are proposed. The first one can realize infinite soft‐switching margin with no restrictions on the transformer magnetizing inductance. The second one can greatly improve the efficiency of the converter. All the theoretical results are verified by a 1‐kW experiment prototype. [ABSTRACT FROM AUTHOR]

LLC resonant converters are widely adopted in many different industrial applications due to their high efficiency operation. To further improve LLC resonant converters' efficiency, the secondary unregulated diode rectifier is replaced by the synchronous rectifier (SR). In many applications, LLC converter is designed to operate at resonant frequency to maximize the system efficiency and act as a DC transformer (DCX). The SR driving signal is set as the same as the primary driving signal to work in an open‐loop mode. However, the resonant frequency will deviate due to the tolerance, working environment, and ageing effect of circuit components, which will lead to the degradation of the system efficiency and output voltage variation. Unfortunately, most of the existing techniques cannot be simply adopted in SR LLC DCX. Therefore, an adaptive SR driving strategy that can compensate the circuit components' variations is necessary for SR LLC DCX. Inan adaptive SR strategy based on the constant voltage gain characteristic at resonant frequency point is proposed. The proposed strategy is applicable for all different scenarios with easy implementation and low cost. [ABSTRACT FROM AUTHOR]

Dielectric quality tests require a high AC voltage with a frequency range of 0.0001 Hz to 1000 Hz. However, providing a high AC voltage with such a frequency variety is challenging. Providing a high DC voltage and then applying such a voltage to an inverter to adjust the frequency can be an acceptable solution for such a challenge. Notably, a high DC voltage is required for DC tests. This study proposes an improved form of the cascaded boost converter, whose merits are as follows: (i) the high voltage gain providing low duty cycles is possible; (ii) the input current is continuous, which decreases the current ripple of the input filter capacitor; (iii) the current stress of the semiconductors is less than the input current, and most of them have a large difference with it; (iv) the voltage stress of the semiconductors is less than the output voltage with a large difference; (v) only one switch with a simple drive circuit is used; (vi) the common ground of the load and input source decreases the EMI noise; (vii) besides the high voltage gain, the voltage density of the converter based on the number of inductors, capacitors, switches, diodes, and whole components is greater than that of the recently proposed converters; (viii) only two stacked connections of the proposed topology can provide a 2.6 kV voltage for a higher DC voltage test of dielectrics. The functional details of the converter are extracted in ideal and continuous conduction (CCM) modes. Moreover, the converter's voltage gain and density are compared with the recently proposed converters to show the superiority of the proposed converter. Finally, the experimental results are presented to validate the theoretical relations in a 140 W output power. [ABSTRACT FROM AUTHOR]

Background: Ultra‐high‐dose‐rate (UHDR) electron beams have been commonly utilized in FLASH studies and the translation of FLASH Radiotherapy (RT) to the clinic. The EDGE diode detector has potential use for UHDR dosimetry albeit with a beam energy dependency observed. Purpose: The purpose is to present the electron beam response for an EDGE detector in dependence on beam energy, to characterize the EDGE detector's response under UHDR conditions, and to validate correction factors derived from the first detailed Monte Carlo model of the EDGE diode against measurements, particularly under UHDR conditions. Methods: Percentage depth doses (PDDs) for the UHDR Mobetron were measured with both EDGE detectors and films. A detailed Monte Carlo (MC) model of the EDGE detector has been configured according to the blueprint provided by the manufacturer under an NDA agreement. Water/silicon dose ratios of EDGE detector for a series of mono‐energetic electron beams have been calculated. The dependence of the water/silicon dose ratio on depth for a FLASH relevant electron beam was also studied. An analytical approach for the correction of PDD measured with EDGE detectors was established. Results: Water/silicon dose ratio decreased with decreasing electron beam energy. For the Mobetron 9 MeV UHDR electron beam, the ratio decreased from 1.09 to 1.03 in the build‐up region, maintained in range of 0.98–1.02 at the fall‐off region and raised to a plateau in value of 1.08 at the tail. By applying the corrections, good agreement between the PDDs measured by the EDGE detector and those measured with film was achieved. Conclusions: Electron beam response of an UHDR capable EDGE detector was derived from first principles utilizing a sophisticated MC model. An analytical approach was validated for the PDDs of UHDR electron beams. The results demonstrated the capability of EDGE detector in measuring PDDs of UHDR electron beams. [ABSTRACT FROM AUTHOR]

This study presents an improved maximum boost control (MBC) method for three-level impedance source inverter. This technique offers removal of sixth frequency component from the inductor current present in the existing MBC technique of ZSI (Impedance Source Inverter). In addition, the proposed technique reduces the common mode voltage to 1/6th of dc bus voltage. The conventional zero vectors of three-level switching diagram are suitably modified and implemented for the case of 3L-CDBCZSI (three level controlled diode bridge clamped based impedance source inverter). It offers increased switching frequency of impedance network and reduces the size of passive components. On the basis of the proposed technique, the merits offered by 3L-CDBCZSI are highlighted and compared with T-type and diode clamped based ZSI. Simulation and experimental results are presented to verify the correctness of the proposed method. [ABSTRACT FROM AUTHOR]

Following successful campaigns on the compact high field spherical tokamak ST40, resistive gold foil bolometers have now been installed to measure the radiated power profile. Positioned on the midplane, two bolometer cameras offer perspectives of the horizontal and vertical planes, while the third camera, situated above the midplane, provides a vertical view of the top divertor plates, including the X-point and the strike points. These cameras use a commercial off-the-shelf data acquisition platform with modules specifically designed for bolometers in a Wheatstone bridge configuration, providing both phase sensitive detection and in situ calibration. This paper presents an overview of the design and functionality of all three cameras and the commissioning of the horizontal plane camera. The commissioning of the horizontal camera shows data from a range of plasma pulses, presenting a positive correlation between the relative profiles measured from the bolometer camera and an absolute extreme ultraviolet diode camera viewing along similar lines of sight. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) in recent years have emerged as a leading display technology and the popularity of OLEDs is attributed to their numerous advantages, including the ability to produce natural color, achieve a true black state, consume low consumption, exhibit fast response, and be compatible with flexible devices. However, limitations in the performance persist, e.g., the out‐coupling efficiency, which currently stands at ≈20% due to issues such as trapped modes and plasmon loss. Many researchers, therefore, have actively proposed the integration of various nanostructures to address the challenges and enhance OLED performance. The structures play a crucial role in facilitating strong optical interaction with surface plasmon and waveguide modes, thereby improving the extraction of trapped modes. To mitigate the confinement, layers to modulate the refractive index are introduced to extract the confined light and redirect it into the out‐coupled mode. In this review, a comprehensive overview of the principle and effectiveness of these nanostructures in enhancing OLED performance is provided. Various applications of OLEDs are explored based on nanostructures such as nanoparticles, nanomeshes, metasurface, bioinspired structures, and scattering layers. By implementing and refining these nanostructures, significant advancements in OLED performance are anticipated. [ABSTRACT FROM AUTHOR]

The performance of the near‐infrared phosphor‐converted light‐emitting diodes (NIR pc‐LEDs) mainly depends on the NIR emitting phosphors used. Cr3+ doped materials can be excited by blue light chips, but their emission is located in the NIR‐I region (650–1000 nm). Ni2+ doped materials are mainly located in the NIR‐II region (1000–1700 nm), but they cannot be effectively excited by blue light chips. Herein, Cr3+, Ni2+ mono‐doped, and co‐doped Sr2GaTaO6 NIR emitting phosphors are prepared and investigated. Cr3+ and Ni2+ ions occupy two octahedral sites of Ga3+ and Ta5+. The co‐doping of Cr3+ ions has achieved two breakthroughs. One is to shift the optimal excitation wavelength from violet light to blue light due to the energy transfer (efficiency up to 70%) from Cr3+ to Ni2+. The other is to achieve the broadband and continuous emission across NIR‐I and NIR‐II regions (650–1700 nm, with a full width at half maximum (FWHM) of 410 nm (173 nm + 237 nm)). The prepared Sr2GaTaO6: 0.02Cr3+, 0.01Ni2+ phosphor is combined with a commercial 460 nm blue chip to realize its application in organic compounds identification, night vision, and biological imaging. This work points out a direction for the future development of efficient super broadband NIR‐emitting phosphors. [ABSTRACT FROM AUTHOR]

Light‐emitting diodes and photodiodes, often acting as transmitters and receivers, are two key optical components for constructing an optical communication system. Recently, solar‐blind optical wireless communication (SB‐OWC) has emerged as a promising free‐space communication platform due to its unique advantages, including low background noise, high security, and non‐line‐of‐sight ability. However, the development of deep ultraviolet (DUV) emitters and detectors is still in its early stages with relatively low efficiency and poor detection capability, which hampers the further progress of SB‐OWC. Herein, a triangular‐shaped micro‐sized diode (T‐μ‐diode) is reported that can significantly boost its DUV emission and detection performance compared with a regular circular‐shaped micro‐diode (C‐μ‐diode) due to improved current injection and enhanced light extraction/absorption behavior. Specifically, the T‐μ‐diodes demonstrate superior light output power with a −3 dB modulation bandwidth over 566 MHz operating at an extremely high current density of 2 kA cm−2 while possessing a higher photo‐responsivity of ≈160 mA W−1 with a faster response speed of 5.1 ns, surpassing the traditional C‐μ‐diodes in both light emitting and detecting modes. Importantly, a bidirectional on‐chip data transmission system is realized by simply switching the operation mode of two T‐μ‐diodes monolithically fabricated on the same platform with boosted emission and detection functionalities. [ABSTRACT FROM AUTHOR]

In recent years, micro-light-emitting diode (micro-LED) displays have attracted much attention due to their high brightness, low power consumption, long lifetime, and fast response. It is considered to have the potential to revolutionize the development direction of next-generation visual display technology. However, the development of micro-LED displays faces numerous issues, primarily due to etching processes for pixel array manufacturing, which cause sidewall damage and decreased photoelectric efficiency. Specifically, these issues are particularly serious when preparing small-sized high-resolution displays. In this work, we effectively overcame the above-mentioned problems by only etching the electron barrier during the preparation process of pixel arrays. The prepared micro-LED display exhibits excellent optoelectronic properties, with the highest brightness and current efficiency reaching 1.66 × 106 nits and 104 cd/A, respectively. The method provides a feasible idea for preparing high-performance micro-LED displays. [ABSTRACT FROM AUTHOR]

For a segmented dynamic wireless power transfer (DWPT) system, when electric vehicles (EVs) move over two adjacent transmitting coils, the received power fluctuates greatly and has some loss. Arming at this problem, this paper proposes a dual receiver segmented DWPT topology to reduce the received power fluctuation of the receiving coil passing through the rail junction during the moving process of the EV. Through magnetic field analysis in this paper, tuning the current phase difference between two adjacent transmitting coils to 180° can enhance the magnetic field. In this paper, a dual receiver series topology (DRST) is designed to pick up power, which consists of four fully controlled components and four diodes. According to EVs' real-time position, the segment DWPT system has three working modes and six working states under the control of DRST. Finally, experiments are carried out. Compared to the single-receiving-coil system, DRST is effective in improving the average output power from 2.007 to 5.657 W and significantly reducing the power fluctuation. [ABSTRACT FROM AUTHOR]

A zero current transition (ZCT) pulse-width modulation (PWM) DC–DC boost converter operating in boundary conduction mode (BCM) is proposed in this paper. The auxiliary circuit of the proposed converter ensures the main switch to turn off with ZCT. Also, due to the operation of the proposed converter in BCM, naturally zero current switching (ZCS) is achieved for the turning on process of the main switch and the turning off process of the main diode. The proposed converter does not contain additional voltage and current stresses across the main components. The operation modes and theoretical analysis of the proposed ZCT PWM DC–DC boost converter operating in BCM are shown in detail. Detailed ZCT cell analysis and selection procedure of the resonant components which ensure the ZCT operation of the main switch are realized. The proposed converter is designed and tested, and experimental results are obtained in the laboratory. The total losses of the proposed converter are decreased by 53.77%, and its efficiency is increased by 3.2% compared to hard switching (HS) converter at 462 W nominal output power. [ABSTRACT FROM AUTHOR]