Soluble processed low-voltage and high efficiency blue phosphorescent organic light-emitting devices using small molecule host systems

We report low voltage driving and highly efficient blue phosphorescence organic light emitting diodes (PHOLEDs) fabricated by soluble process. A soluble small molecule mixed host system consisting of hole transporting 4,4’,4’’ tris(N-carbazolyl)triphenylamine (TCTA) and bipolar carrier transporting 2,6-bis(3-(carbazol-9-yl)phenyl)pyridine (26DCzPPy) exhibits high solubility with smooth surface properties. Moreover, this small molecule host shows the smoothest morphological property similar to a vacuum deposited amorphous film. A low driving voltage of 5.4 V at 1000 cd/m² and maximum external quantum efficiency 14.6% obtained in the solution processed blue PHOLEDs are useful for large area low cost manufacturing.     

Ag/Ni Metallization Bilayer: A Functional Layer for Highly Efficient Polycrystalline SnSe Thermoelectric Modules

The structural and electrical characteristics of Ag/Ni bilayer metallization on polycrystalline thermoelectric SnSe were investigated. Two difficulties with thermoelectric SnSe metallization were identified for Ag and Ni single layers: Sn diffusion into the Ag metallization layer and unexpected cracks in the Ni metallization layer. The proposed Ag/Ni bilayer was prepared by hot-pressing, demonstrating successful metallization on the SnSe surface without interfacial cracks or elemental penetration into the metallization layer. Structural analysis revealed that the Ni layer reacts with SnSe, forming several crystalline phases during metallization that are beneficial for reducing contact resistance. Detailed investigation of the Ni/SnSe interface layer confirms columnar Ni-Sn intermetallic phases [(Ni₃Sn and Ni₃Sn₂) and Ni_5.63SnSe₂] that suppress Sn diffusion into the Ag layer. Electrical specific-contact resistivity (5.32 × 10^?4 Ω cm²) of the Ag/Ni bilayer requires further modification for development of high-efficiency polycrystalline SnSe thermoelectric modules.     

Chemiluminescent and Antioxidant Micelles as Theranostic Agents for Hydrogen Peroxide Associated‐Inflammatory Diseases

Hydrogen peroxide (H₂O₂) is one of essential oxygen metabolites in living organisms, but is generated in large amounts during inflammatory responses. Therefore, H₂O₂ has great potential as diagnostic and therapeutic markers of several inflammatory and life‐threatening diseases. Here, chemiluminescent and antioxidant micelles are reported as novel theranostic agents for H₂O₂‐associated inflammatory diseases. The chemiluminescent micelles composed of amphiphilic block copolymer Pluronic F‐127, hydroxybenzyl alcohol‐incorporated copolyoxalate (HPOX) and fluorescent dyes perform peroxalate chemiluminescence reactions to detect H₂O₂ as low as 100 nM and image H₂O₂ generated in inflamed mouse ankles. The micelles encapsulating HPOX reduce the generation of reactive oxygen species in lipopolysaccharide (LPS)‐activated macrophages by scavenging overproduced H₂O₂ and releasing antioxidant hydroxybenzyl alcohol (HBA). They also exert inhibitory effects on H₂O₂‐induced apoptosis. HPOX‐based chemiluminescent and antioxidant micelles have great potential as a theranostic agent for H₂O₂‐associated inflammatory diseases.     

Fabrication of Superjunction Trench Gate Power MOSFETs Using BSG‐Doped Deep Trench of p‐Pillar

In this paper, we propose a superjunction trench gate MOSFET (SJ TGMOSFET) fabricated through a simple p pillar forming process using deep trench and boron silicate glass doping process technology to reduce the process complexity. Throughout the various boron doping experiments, as well as the process simulations, we optimize the process conditions related with the p pillar depth, lateral boron doping concentration, and diffusion temperature. Compared with a conventional TGMOSFET, the potential of the SJ TGMOSFET is more uniformly distributed and widely spread in the bulk region of the n drift layer due to the trenched p‐pillar. The measured breakdown voltage of the SJ TGMOSFET is at least 28% more than that of a conventional device.     

Scheduling with accurate communication delay model and scheduler implementation for multiprocessor system-on-chip

In multiprocessor system-on-chip, tasks and communications should be scheduled carefully since their execution order affects the performance of the entire system. When we implement an MPSoC according to the scheduling result, we may find that the scheduling result is not correct or timing constraints are not met unless it takes into account the delays of MPSoC architecture. The unexpected scheduling results are mainly caused from inaccurate communication delays and or runtime scheduler’s overhead. Due to the big complexity of scheduling problem, most previous work neglects the inter-processor communication, or just assumes a fixed delay proportional to the communication volume, without taking into consideration subtle effects like the communication congestion and synchronization delay, which may change dynamically throughout tasks execution. In this paper, we propose an accurate scheduling model of hardware/software communication architecture to improve timing accuracy by taking into account the effects of dynamic software synchronization and detailed hardware resource constraints such as communication congestion and buffer sharing. We also propose a method for runtime scheduler implementation and consider its performance overhead in scheduling. In particular, we introduce efficient hardware and software scheduler architectures. Furthermore, we address the issue of centralized implementation versus distributed implementation of the schedulers. We investigate the pros and cons of the two different scheduler implementations. Through experiments with significant demonstration examples, we show the effectiveness of the proposed approach.     

Soldering method using longitudinal ultrasonic

An efficient ultrasonic soldering method of inserting the metal bumps into the solder is investigated in this work for electronic packaging. The effects of the process parameters such as the ultrasonic frequency, amplitude, dimensions of the metal bump and solder are analyzed through the viscoelastic modeling. The ultrasonic soldering was conducted using the Cu and Au bumps, and the acceptable bonding condition was determined from the tensile strength. Localized heating of the solder was achieved and the stirring action due to the ultrasonic influences the bond strength and microstructure of the eutectic solder. Since higher temperature is obtained with smaller solder, the proposed ultrasonic soldering method appears to be applicable to the high-density electronic packaging.     

Sensitivity analysis of ion implanted silicon wafers after rapid thermal annealing

In this study, we have investigated sensitivities of the ion implanted silicon wafers processed by rapid thermal annealing (RTA), which can reveal the variation of sheet resistance as a function of annealing temperature as well as implantation parameters. All the wafers were sequentially implanted by the arsenic or phosphorous implantations at 40, 80, and 100 keV with the dose level of 10¹⁴ to 2 × 10¹⁶ ions/cm². Rapid thermal annealing was carried out for 10 s by the infrared irradiation at a temperature between 850 and 1150°C in the nitrogen ambient. The activated wafer was characterized by the measurements of the sheet resistance and its uniformity mapping. The values of sensitivities are determined from the curve fitting of the experimental data to the fitting equation of correlation between the sheet resistance and process variables. From the sensitivity values and the deviation of sheet resistance, the optimum process conditions minimizing the effects of straggle in process parameters are obtained. As a result, a strong dependence of the sensitivity on the process variables, especially annealing temperatures and dose levels is also found. From the sensitivity analysis of the 10 s RTA process, the optimum values for the implant dose and annealing temperature are found to be in the range of 10¹⁶ ions/cm² and 1050-1100°C, respectively. The sensitivity analysis of sheet resistance will provide valuable data for accurate activation process, offering a guideline for dose monitoring and calibration of ion implantation process.     

Ultra‐small Form‐Factor Helix on Pad‐Type Stage‐Bypass WCDMA Tx Power Amplifier Using a Chip‐Stacking Technique and a Multilayer Substrate

A fully integrated small form‐factor HBT power amplifier (PA) was developed for UMTS Tx applications. For practical use, the PA was implemented with a well configured bottom dimension, and a CMOS control IC was added to enable/disable the HBT PA. By using helix‐on‐pad integrated passive device output matching, a chip‐stacking technique in the assembly of the CMOS IC, and embedding of the bulky inductive lines in a multilayer substrate, the module size was greatly reduced to 2 mm × 2.2 mm. A stage‐bypass technique was used to enhance the efficiency of the PA. The PA showed a low idle current of about 20 mA and a PAE of about15% at an output power of 16 dBm, while showing good linearity over the entire operating power range.     

Highly Efficient Green ZnAgInS/ZnInS/ZnS QDs by a Strong Exothermic Reaction for Down‐Converted Green and Tripackage White LEDs

Highly efficient bright green‐emitting Zn?Ag?In?S (ZAIS)/Zn?In?S (ZIS)/ZnS alloy core/inner‐shell/shell quantum dots (QDs) are synthesized using a multistep hot injection method with a highly concentrated zinc acetate dihydrate precursor. ZAIS/ZIS/ZnS QD growth is realized via five sequential steps: a core growth process, a two‐step alloying–shelling process, and a two‐step shelling process. To enhance the photoluminescence quantum yield (PLQY), a ZIS inner‐shell is synthesized and added with a band gap located between the ZAIS alloy‐core and ZnS shell using a strong exothermic reaction. The synthesized ZAIS/ZIS/ZnS QDs shows a high PLQY of 87% with peak wavelength of 501 nm. Tripackage white down‐converted light‐emitting diodes (DC‐LEDs) are realized using an InGaN blue (B) LED, a green (G) ZAIS/ZIS/ZS QD‐based DC‐LED, and a red (R) Zn?Cu?In?S/ZnS QD‐based DC‐LED with correlated color temperature from 2700 to 10 000 K. The red, green, and blue tripackage white DC‐LEDs exhibit high luminous efficacy of 72 lm W^?1 and excellent color qualities (color rendering index (CRI, R_a) = 95 and the special CRI for red (R₉) = 93) at 2700 K.     

Wearable Force Touch Sensor Array Using a Flexible and Transparent Electrode

Transparent electrodes have been widely used for various electronics and optoelectronics, including flexible ones. Many nanomaterial‐based electrodes, in particular 1D and 2D nanomaterials, have been proposed as next‐generation transparent and flexible electrodes. However, their transparency, conductivity, large‐area uniformity, and sometimes cost are not yet sufficient to replace indium tin oxide (ITO). Furthermore, the conventional ITO is quite rigid and susceptible to mechanical fractures under deformations (e.g., bending, folding). In this study, the authors report new advances in the design, fabrication, and integration of wearable and transparent force touch (touch and pressure) sensors by exploiting the previous efforts in stretchable electronics as well as novel ideas in the transparent and flexible electrode. The optical and mechanical experiment, along with simulation results, exhibit the excellent transparency, conductivity, uniformity, and flexibility of the proposed epoxy‐copper‐ITO (ECI) multilayer electrode. By using this multi‐layered ECI electrode, the authors present a wearable and transparent force touch sensor array, which is multiplexed by Si nanomembrane p‐i‐n junction‐type (PIN) diodes and integrated on the skin‐mounted quantum dot light‐emitting diodes. This novel integrated system is successfully applied as a wearable human–machine interface (HMI) to control a drone wirelessly. These advances in novel material structures and system‐level integration strategies create new opportunities in wearable smart displays.