Conventional Planar Structure Research Articles

Improved Charge Injection Balance in Quantum Dot Light-Emitting Diodes through Interface Texture.

The existing methods to improve the charge balance of quantum dot light-emitting diodes (QLEDs) rely on energy-level matching, but these approaches have been limited by material availability and Fermi-level pinning. Here, we propose a solution that does not require changes to the materials' electronic properties. By using nanoimprinting technology to texture the interface between the hole-transporting layer (HTL) and colloidal quantum dot (CQD) layer, we can increase the HTL-CQD contact area. This significantly enhances the hole injection rate while keeping the electron injection rate essentially unchanged. Compared with the conventional planar structure, QLEDs with textured HTL exhibit lower luminance threshold voltage, significantly higher external quantum efficiency at low bias voltages, improved operational stability, and a similar Lambertian factor. Comprehensive measurements confirm that the HTL-CQD interface texture allows more efficient hole injection into CQDs to occur under lower bias, resulting in less CQD charging and more efficient exciton recombination.

A novel array current collector design enabling high energy efficiency liquid metal batteries

Liquid metal battery (LMB) is one of the most competitive large-scale energy storage technologies due to its low-cost, long-lifespan, and high-safety. However, the low energy efficiency of the battery is currently one of the major challenges hindering its application process. The problem of poor wettability of the cathode liquid alloy is exacerbated by the design of the conventional planar structure of the positive collector. And the resulting interfacial mass transfer modes are inefficient. These lead to slow electrode reaction kinetics and large internal polarization. To address this issue, a novel array current collector suitable for LMB was designed here for the first time. The unique structure of the collector greatly increases the effective reaction area at the electrolyte/cathode and the contact area of the cathode/collector, providing more efficient nucleation and growth modes of the products as well as richer ionic mass-transfer channels, thus accelerating the electrode reaction kinetics. Benefiting from the application of the array current collector, the voltage efficiency of Li||Sb-Sn LMBs with a capacity of 20 Ah at 0.5C rate is increased by 4.8 %. Meanwhile, an average voltage efficiency of ∼ 94.7 % and an average energy efficiency of ∼ 92.2 % are achieved at 0.1C, which is the highest efficiency among the most promising LMB systems known to date. These encouraging results provide new directions for the design of high-performance LMBs and further promote the practical process of LMBs.

Characteristics of eco-friendly perovskite solar cell with moth-eye nanostructure array

A novel design of tin perovskite (CH3NH3SnI3) solar cell (PSC) is proposed and analyzed for energy harvesting application. The suggested PSC is lead free where moth-eye nanostructures are implemented in the active material to improve the light trapping and hence the light absorption. The suggested SC is numerically studied using finite difference time domain (FDTD) via Lumerical software package. The geometrical parameters and position of the nanostructures are studied to maximize the absorption and hence the optical efficiency. The reported PSC covered by the moth-eye nanostructures exhibits marked light trapping compared to the conventional planar structure with photocurrent density of 46.0082 (mA/cm2), an optical generation rate of 3.38 e28 (m−3. s−1) and an ultimate efficiency of 31.76%. Therefore, an enhancement of 14.496% is obtained compared to the traditional PSC due to the localized surface plasmons (LSP) modes around the moth eye nanostructures. The suggested design is an efficient replacement to lead—perovskite owing to excellent photovoltaic properties, cheap fabrication cost, suitable band gap of 1.02 eV, eco-friendly and great performance in converting sunlight to electrical energy.

A Novel Conformal Quasi-Yagi Antenna With Offset Feed for High Directional 300GHz Applications

This communication reports a conformal offset feed Quasi-Yagi antenna at 300 GHz for high-directional applications. A novel offset feed mechanism is adopted to obtain directional behavior from a conventional planar structure. The proposed antenna is designed on a Silicon-dioxide (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) dielectric substrate having a permittivity (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ) of 4 and a height of 60μm. A gold material of thickness 5μm is used as a conducting metal in the top and bottom layers. This antenna consists of an offset feed patch, partial ground as a reflector, and three director elements forming a Quasi-Yagi antenna. This conformal structure operates from 270 GHz to 333 GHz and provides a peak gain of 8.62dBi at 300 GHz in the end-fire direction. An analysis of different metals and parametric variation in metal thickness, substrate thickness, patch length, and width is also reported for a better understanding of the evolution of the proposed structure. A lumped equivalent circuit is also developed for the proposed structure to study its transmission line model. A good agreement is also noted between the EM simulation (HFSS, CST) and circuit simulation (ADS).

Effect of the Indium Compositions in Tri-Gate InxGa1−xAs HEMTs for High-Frequency Low Noise Application

In this paper, we investigated the tri-gate InxGa1−xAs high electron mobility transistors (HEMTs) with different indium compositions for low noise applications. The tri-gate configuration in this work exhibits better device performances of the transconductance (gm), the current gain cutoff frequency (fT), the maximum oscillation frequency (fmax), and the minimum noise figure compared with the conventional planar structure due to the improved gate controllability. The indium contents of 20%, 40%, and 100% tri-gate devices were also fabricated for comparison. The resistances and leakage current were measured to investigate the effect between the indium compositions and the noise figure. Experimental results exhibited that the tri-gate In0.4Ga0.6As mHEMT with neither the highest transconductance nor the lowest gate leakage current exhibited the lowest minimum noise figure (NFmin) of 2 dB when operating at 50 GHz. The study reveals that device architecture and indium composition are important factors in the determination of noise performance.

Modeling and characteristics of a nanostructured NiO/GeSe core–shell perovskite solar cell

Inorganic–organic hybrid perovskite solar cells (PSCs) have recently seen considerable progress, and this has encouraged researchers to evolve and test numerous different and potentially improved device architectures. As a result, in this paper, a theoretical design for improving light absorption to obtain maximum photocurrent using NiO/GeSe core–shell nanostructures is introduced. The effects of using nanostructure arrays, based on the light trapping technique, on the light absorption, generation of carriers, absorption field profiles, and finally the photocurrent density of PSCs, have been investigated through a three-dimensional finite-difference time-domain approach. By selecting NiO and GeSe as the core and the shell materials, the absorption of the active layer has been increased, relative to the use of a conventional planar structure. This core–shell nanostructure leads to a reduction in the carrier recombination within the PSC proposed design. The results obtained from our simulation show that the device performance is highly dependent on the height and materials used in the core–shell. Significantly, an optimal height of 160 nm was obtained for core–shell in a PSC design with a J ph value of 27.23 m A / c m 2 .

Nanoslot metasurface design and characterization for enhanced organic light-emitting diodes

We investigate bottom-emitting organic light-emitting diodes (B-OLEDs) integrated with metasurface (MS) to analyze the effect of the structural parameters on the output performance. The performance of the MS-integrated B-OLED (MIB-OLED) is evaluated by out-coupling efficiency (OCE) and reflection of the ambient light, while attention is paid mainly to dielectric capping and metal structure of MS that may influence excitation of surface plasmon (SP). The results suggest that layer thicknesses affect the performance by as much as 10% for the OCE and up to 32% for reflectance. The OCE is in general weakly affected by the structural parameters of MS. In contrast, the reflectance characteristics are found to be dominated by localized SP that is largely determined by the length and the width of a unit slot of MS. An optimization factor introduced to evaluate the performance based on out-coupling power to the radiation mode and reflectance of MIB-OLEDs confirms that integration with MS improves performance by 16% over conventional planar structure. In particular, MIB-OLED is found to enhance OCE by 51% with Lambertian-like pattern. Enhanced performance is experimentally confirmed. The findings provide insights on how to optimize the MS structure to produce MIB-OLEDs with enhanced out-coupled power and contrast ratio.

3D Printing of Electrochemical Energy Storage Devices: A Review of Printing Techniques and Electrode/Electrolyte Architectures

AbstractRecently, the fabrication of electrochemical energy storage (EES) devices via three‐dimensional (3D) printing has drawn considerable interest due to the enhanced electrochemical performances that arise from well‐designed EES device architectures as compared to the conventionally fabricated ones. This work summarizes the developments in electrochemical devices fabricated by 3D printing techniques. We have categorized this review based on the architectural design of 3D printed EES devices: interdigitated structures, 3D scaffolds, and fibers. The printing techniques, processes, printing materials, advantages, and disadvantages of 3D printed architectures are systematically discussed in this review. Enhanced power density and energy density values were obtained using interdigitated structures and 3D scaffolds, in comparison with the conventional planar structure. The reasons for better electrochemical performances can be attributed to the presence of higher loading active materials, larger footprint area, and shorter ion transport route. The 3D printing techniques have also enabled the EES devices to be fabricated into lightweight, flexible fibers, and to be integrated into wearable electronics. At the end, the challenges and outlooks on the fabrication of 3D structured EES devices are outlined.

Improvement in Luminous Efficacy and Thermal Performance Using Quantum Dots Spherical Shell for White Light Emitting Diodes.

White light-emitting diodes (WLEDs) based on quantum dots (QDs) are gaining increasing attention due to their excellent color quality. QDs films with planar structure are universally applied in WLEDs for color conversion, while they still face great challenges in high light extraction and thermal stability. In this study, a QDs film with a spherical shell structure was proposed to improve the optical and thermal performance for WLEDs. Compared with the conventional planar structure, the luminous efficacy of the QDs spherical shell structure is improved by 12.9% due to the reduced total reflection effect, and the angular-dependent correlated color temperature deviation is decreased from 2642 to 283 K. Moreover, the highest temperature of the WLED using a QDs spherical shell is 4.8 °C lower than that of the conventional WLED with a planar structure, which is mainly attributed to larger heat dissipation area and separated heat source. Consequently, this QDs spherical shell structure demonstrates superior performance of QDs films for WLEDs applications.

U‐shaped stacked structure monolithic transformer for efficiency improvement

AbstractThis article presents a novel monolithic transformer (TF) structure, which is designed to improve TF efficiency by enhancing the quality factor of the metal trace. When the number of thick metal layers is limited in semiconductor technology, it is necessary to use thin metals that have lower quality factors to form the TF coil, which degrades TF efficiency. To overcome this limitation, supplementary walls of metal and a via are connected along both sides of the thin metal to form a U‐shaped metal trace, which in turn improves the quality factor and TF efficiency. The proposed structure does not require additional metal layers, other than the metal layers used in the TF configuration. Thus, the proposed structure is widely applicable to all semiconductor technologies, including those that provide only a small number of metal layers. To assess and validate this proposed structure, we fabricated a set of TFs including conventional structures using gallium arsenide (GaAs) technology, which is the most widely used technology in mobile power amplifier (PA) fabrication. The proposed structure was successfully demonstrated to effectively improve the TF efficiency by as much as 8.6% and 6.5% in comparison to a conventional planar structure and a stacked structure, respectively.

Single-event burnout hardening of planar power MOSFET with partially widened trench source * * Project supported by the National Natural Science Foundation of China (Nos. 61404161, 61404068, 61404169).

We present a single-event burnout (SEB) hardened planar power MOSFET with partially widened trench sources by three-dimensional (3D) numerical simulation. The advantage of the proposed structure is that the work of the parasitic bipolar transistor inherited in the power MOSFET is suppressed effectively due to the elimination of the most sensitive region (P-well region below the N+ source). The simulation result shows that the proposed structure can enhance the SEB survivability significantly. The critical value of linear energy transfer (LET), which indicates the maximum deposited energy on the device without SEB behavior, increases from 0.06 to 0.7 pC/μm. The SEB threshold voltage increases to 120 V, which is 80% of the rated breakdown voltage. Meanwhile, the main parameter characteristics of the proposed structure remain similar with those of the conventional planar structure. Therefore, this structure offers a potential optimization path to planar power MOSFET with high SEB survivability for space and atmospheric applications.

Single crystal diamond UV detector with a groove-shaped electrode structure and enhanced sensitivity

An ultraviolet (UV) detector on single crystal chemical vapor deposition (CVD) diamond with three-dimensional (3D) metal electrodes, is designed, and fabricated with the aim to improve collection efficiency of photo-induced carriers. Interdigitated Ti/Au electrodes were formed within 10μm deep groove etched in diamond to ensure a more uniform field pattern in the diamond bulk. In the preliminary tests the groove-shaped 3D device performance was compared to a detector with a conventional planar structure on the same material at applied electric field of 1V/μm. It is found that the responsivity of the 3D electrode structure in the spectral range of 220–280nm is up to 50% higher than that for the planar structure.

New advances in small molecule hole-transporting materials for perovskite solar cells

Organic π-functional molecules are the foundation and basic component of organic optoelectronic devices. For example, for ideal carrier transporting materials, extended π-conjugation and ordered π–π stacking are necessary to enhance the charge mobility and achieve desirable results. As a promising way to convert sunlight into electricity, organometal halide perovskite solar cells (PSCs) have captured a lot of attention due to its predominant merits especially in the aspect of remarkable photovoltaic performance and much potentially low production cost. For conventional planar PSC structure, hole-transporting layer which typically consists of organic π-functional materials plays a key role in suppressing hole–electron pair recombination, promoting charge transporting and ensuring ohmic contact of back electrode. Considering the key roles of HTMs and its soaring progress in recent years, here, we will summarize recent progress in small organic π-functional materials from its diverse functions in PSCs. Besides, aiming to further promote the development of organic π-functional molecules and HTMs, a promising direction toward highly efficient HTMs will also be discussed.

Electrical Behavior of X-Ray Detector Based on PbI2Crystal With Coplanar Electrode Structure

In this work, we report on the results of the electrical behavior of coplanar electrode structure X-ray detector based on PbI2 crystal. The detector with coplanar electrode similar to the Van der Pauw structure instead of conventional planar structure can partly reduce the influence of trapping effect to charge carrier transport along the $c$ -axis. According to the configuration, four operating modes of the detector were thoroughly studied. Several novel results, such as the negative polarity dark current and photocurrent under zero bias voltage, orientation polarization, short relaxation time of steady-state surface leakage current and fast photocurrent response are obtained by this kind of coplanar structure configuration. The detector has the potential to be developed as a solid state X-ray dosimeter in the medical radiation environment, providing a high sensitivity and good adaptability under positive or negative bias voltage.

Influence of curved surface on properties of metamaterial absorber

We numerically investigate the influence of curved surface on the properties of metamaterial absorber in the microwave regime. It is shown that curved surface metamaterial absorber can lead to dramatic absorption increase compared with the conventional planar structure. Simulation results demonstrate that the proposed absorber can perform absorption peaks at two resonant frequencies and one resonant frequency for the TM and TE polarizations, respectively. This simple absorber is particularly desirable for various potential applications such as improving absorbance performances.

Trench Multiple Floating Limiting Rings Termination for 4H-SiC High-Voltage Devices

A junction termination method adopting heavily doped p-well rings with a shallow trench for each ring, named as a trench multiple floating limiting rings (TMFLRs), is analyzed and fabricated without any additional process in 4H-SiC junction barrier Schottky diode. A breakdown voltage of 6.7 kV is achieved using TMFLRs structure on an epitaxial layer with thickness of 50 $\mu \text{m}$ , while the breakdown voltage of the conventional planar FLRs structure with the same termination area is only 5.7 kV. The experimental result has demonstrated that the TMFLRs termination structure yields about 90% of the parallel plane breakdown voltage. In addition, the simulation results show that the TMFLRs make the bulk peak electric field ( $E_{p,\text {bulk}})$ reduce and move away from the device surface, successfully making the interface peak electric field ( $E_{p,\text {interface}})$ decrease by about 30% compared with a conventional planar FLRs structure when same reverse voltages applied.

Trench-gate-integrated superjunction lateral double-diffused MOSFET with low specific on-resistance

In this paper, a new low-voltage planar gate superjunction (SJ) lateral double-diffused MOSFET (LDMOSFET) is presented. The proposed trench-gate-integrated SJ-LDMOSFET is composed of a conventional planar gate structure and a trench gate structure extending into a drift region through a channel region, which helps reduce both drift resistance and channel resistance. By device simulation, we confirmed that current crowding near the top surface was alleviated by the spread of electron current into the drift region through the accumulation layer of the trench gate. As a result, the specific on-resistance (RON · A) of the trench-gate-integrated SJ-LDMOSFET can be reduced by increasing SJ thickness (TSJ), and the trench-gate-integrated SJ-LDMOSFET with a TSJ of 4 µm achieved an RON · A of 0.47 mΩ·cm2 at a breakdown voltage of 97 V. This is about 14% lower than the one-dimensional Si limit.

Novel Gate-All-Around High-Voltage Thin-Film Transistor With T-Shaped Metal Field Plate Design

A novel gate-all-around (GAA) high-voltage thin-film transistor (HVTFT) with the T-shaped metal field plate (MFP) design results in a high breakdown voltage ( $V_{\rm BD})_{_{_{}}}$ of 119.9 V and a low specific ON-resistance ( $R_{\rm SP})$ of 8.4 m $\Omega \cdot ~\mathrm{cm}^{2}$ . This T-shaped MFP GAA HVTFT solves the $V_{{\rm {BD}}}$ – $R_{\rm SP}$ tradeoff problems and exhibits superior gate control performance, which leads to excellent electrical characteristics such as a better ON/OFF ratio of $> 10^{10}$ and a lower subthreshold slope of 154.4 mV/decade than the conventional planar structure.

3-D Simulation and Optimization of Organic Solar Cell With Periodic Back Contact Grating Electrode

In this paper, we report an investigation of the optical and electrical properties of an organic solar cell (OSC) with a back contact grating architecture through 3-D numerical simulations. By using finite-element methods for both optical and transport properties, we have modeled the behavior of OSC with a grating architecture and compared with a conventional planar structure. Based on these optoelectrical simulations, we optimized the back contact grating, obtaining an increment of up to 17.5% in power conversion efficiency with respect to a planar structured OSC. This enhancement is the result of an increase of both short-circuit current and fill factor.

A COMPACT FOURTH-ORDER MULTI-FOLD HAIRPIN LINE MICROSTRIP BANDPASS FILTER AT 1650 MHZ FOR RF/ WIRELESS COMMUNICATIONS

This paper describes the design, simulation/optimization and measured results of a fourth-order multi-folded hairpin line microstrip bandpass filter at 1650 MHz, with 60-65% reduction in size compared to the structure of a basic hairpin line microstrip bandpass filter. The imperical equations and relevant graphs have been used to realize adjacent and cross couplings between the four multi-folded resonators. A conventional hairpin-line resonator size is normally very large. The folded hairpin line resonator filters are compact, small sized and simple to design and fabricate. The proposed multi-folded hairpin line microstrip filter is a slow wave open loop type narrow band, high selectivity, small sized and low cost band pass filter for RF/wireless trans/receive communication systems for ground and space applications in L-band. The cross couplings have been realized between adjacent and non-adjacent resonators. The ADS-Agilent make software have been used to design and simulate the filters having the folded hairpin line resonators. The measured results are very close to the simulated results, with great reduction in size compared to the conventional planar hairpin line structure.