A zero-voltage and zero-current switching full bridge DC-DCconverter with transformer isolation

A new primary-side-assisted zero-voltage and zero-current switching full bridge DC-DC converter with transformer isolation is proposed. The proposed DC-DC converter uses only one auxiliary transformer and two diodes to obtain ZCS for the leading leg. It has a simple and robust structure, and load current control capability even in short circuit conditions, The possibility of magnetic saturation due to asymmetricity of circuits or transient phenomena is greatly reduced, which is a very attractive feature in DC-DC converters with transformer isolation. The power rating of the auxiliary transformer is about 10% of that of the main transformer. Operation of a 12 kW prototype designed for welding application was verified by experiments     

Design and Synthesis of CdHgSe/HgS/CdZnS Core/Multi-Shell Quantum Dots Exhibiting High-Quantum-Yield Tissue-Penetrating Shortwave Infrared Luminescence

Cd_xHg_1−xSe/HgS/Cd_yZn_1−yS core/multi-shell quantum dots (QDs) exhibiting bright tissue-penetrating shortwave infrared (SWIR; 1000–1700 nm) photoluminescence (PL) are engineered. The new structure consists of a quasi-type-II Cd_xHg_1−xSe/HgS core/inner shell domain creating luminescent bandgap tunable across SWIR window and a wide-bandgap Cd_yZn_1−yS outer shell boosting the PL quantum yield (QY). This compositional sequence also facilitates uniform and coherent shell growth by minimizing interfacial lattice mismatches, resulting in high QYs in both organic (40–80%) and aqueous (20–70%) solvents with maximum QYs of 87 and 73%, respectively, which are comparable to those of brightest visible-to-near infrared QDs. Moreover, they maintain bright PL in a photocurable resin (QY 40%, peak wavelength ≈ 1300 nm), enabling the fabrication of SWIR-luminescent composites of diverse morphology and concentration. These composites are used to localize controlled amounts of SWIR QDs inside artificial (Intralipid) and porcine tissues and quantitatively evaluate the applicability as luminescent probes for deep-tissue imaging.     

20% External Quantum Efficiency in Solution‐Processed Blue Thermally Activated Delayed Fluorescent Devices

Highly efficient solution‐processed blue thermally activated delayed fluorescent (TADF) devices are developed by designing soluble blue TADF emitters. The solubility and emission color could be managed by introducing F as an electron withdrawing unit instead of CN. Two soluble blue TADF emitters are synthesized and show a high external quantum efficiency of 20.0% with a color coordinate of (0.16,0.26), and it is the best quantum efficiency reported in solution‐processed TADF devices. The device performances of the solution‐processed blue TADF devices are comparable to those of vacuum‐processed blue TADF devices.     

InGaN microring light-emitting diodes

The fabrication and performance of an InGaN light-emitting diode (LED) array based on a microring device geometry is reported. This design has been adopted in order to increase the surface area for light extraction and to minimize losses due to internal reflections and reabsorption. Electrical characteristics of these devices are similar to those of a conventional large-area LED, while the directed light extraction proves to be superior. In fact, these devices are found to be more efficient when operated at higher currents. This may be attributed to improved heat sinking due to the large surface area to volume ratio. The potential applications of these devices are also discussed.     

Mucoadhesive Phenolic Pectin Hydrogels for Saliva Substitute and Oral Patch

Oral disease is one of the most common conditions worldwide, negatively affecting general health, reducing the quality of life, and often developing into systemic illness. However, the design of therapeutic agents for oral diseases is challenging due to various unique features of the oral cavity, including its wet and dynamic environment and curved shape. Herein, the development of highly biocompatible mucoadhesive functional hydrogels for oral applications is reported, generated by introducing bio-inspired phenolic moieties into a pectin polymer. Pyrogallol-functionalized pectin (Pec-PG) can be crosslinked in situ via autoxidation without chemical agents and readily fabricated as various formulations. Sprayable Pec-PG hydrogel exhibits strong mucoadhesion and outstanding hydration ability ex vivo and in vivo, thus displaying significant potential as a novel saliva substitute for dry mouth. The authors further show that topical application of mucoadhesive Pec-PG patches pre-loaded with corticosteroid significantly promotes the repair of diabetic oral ulcer tissue via prolonged drug release, free radical scavenging, and physical barrier effects. Moreover, similar applications for oral ulcer treatment using a pectin hydrogel modified with catechol (Pec-CA), another phenolic moiety are demonstrated. Together, these findings suggest that mucoadhesive phenolic pectin derivatives can provide highly biocompatible, convenient, and effective hydrogel platforms for treating oral diseases.     

Efficiency optimization of green phosphorescent organic light-emitting device

Using a narrow band gap host of bis[2-(2-hydroxyphenyl)-pyridine]beryllium (Bepp₂) and green phosphorescent Ir(ppy)₃ [fac-tris(2-phenylpyridine) iridium III] guest concentration as low as 2%, high efficiency phosphorescent organic light-emitting diode (PHOLED) is realized. Current and power efficiencies of 62.5 cd/A (max.), 51.0 lm/W (max.), and external quantum efficiency (max.) of 19.8% are reported in this green PHOLED. A low current efficiency roll-off value of 10% over the brightness of 10,000 cd/m² is noticed in this Bepp₂ single host device. Such a high efficiency is obtained by the optimization of the doping concentration with the knowledge of the hole trapping and the emission zone situations in this host-guest system. It is suggested that the reported device performance is suitable for applications in high brightness displays and lighting.