Dynamic Network Characteristics of Power-electronics-based Power Systems

Power flow studies in traditional power systems aim to uncover the stationary relationship between voltage amplitude and phase and active and reactive powers; they are important for both stationary and dynamic power system analysis. With the increasing penetration of large-scale power electronics devices including renewable generations interfaced with converters, the power systems become gradually power-electronics-dominant and correspondingly their dynamical behavior changes substantially. Due to the fast dynamics of converters, such as AC current controller, the quasi-stationary state approximation, which has been widely used in power systems, is no longer appropriate and should be reexamined. In this paper, for a better description of network characteristics, we develop a novel concept of dynamic power flow and uncover an explicit dynamic relation between the instantaneous powers and the voltage vectors. This mathematical relation has been well verified by simulations on transient analysis of a small power-electronics-based power system, and a small-signal frequency-domain stability analysis of a voltage source converter connected to an infinitely strong bus. These results demonstrate the applicability of the proposed method and shed an improved light on our understanding of power-electronics-dominant power systems, whose dynamical nature remains obscure

Nano-to-microporous networks via inkjet printing of ZnO nanoparticles/graphene hybrid for ultraviolet photodetectors

Inkjet-printed photodetectors have gained enormous attention over the past decade. However, device performance is limited without postprocessing, such as annealing and UV exposure. In addition, it is difficult to manipulate the surface morphology of the printed film using an inkjet printer because of the limited options of low viscosity ink solutions. Here, we employ a concept involving the control of the inkjet-printed film morphology via modulation of cosolvent vapor pressure and surface tension for the creation of a high-performance ZnO-based photodetector on a flexible substrate. The solvent boiling point across different cosolvent systems is found to affect the film morphology, which results in not only distinct photoresponse time but also photodetectivity. ZnO-based photodetectors were printed using different solvents, which display a fast photoresponse in low-boiling point solvents because of the low carbon residue and larger photodetectivity in high-boiling point solvent systems due to the porous structure. The porous structure is obtained using both gas–liquid surface tension differences and solid–liquid surface differences, and the size of porosity is modulated from nanosize to microsize depending on the ratio between two solvents or two nanomaterials. Moreover, the conductive nature of graphene enhances the transport behavior of the photocarrier, which enables a high-performance photodetector with high photoresponsivity (7.5 × 102AW–1) and fast photoresponse (0.18 s) to be achieved without the use of high-boiling point solvents

Hybrid passivation for foldable indium gallium zinc oxide thin-film transistors mediated by low-temperature and low-damage parylene-C/atomic layer deposition-AlOx coating

Indium gallium zinc oxide (IGZO) thin‐film transistors (TFTs) are primary components in active integrated electronics, such as displays and sensor arrays, which heavily involve high‐throughput passivation techniques during multilayer fabrication processes. Though oxide compound semiconductors are commonly used for providing uniform and robust passivation, it usually causes performance degradation on IGZO TFTs during passivation process. Herein, a parylene‐C and aluminum oxide (AlOx) hybrid passivation approach are introduced to reduce the damage during AlOx atomic layer deposition (ALD), which results in high‐performance depletion‐mode IGZO TFT to be fabricated on polyethylene naphthalate (PEN) substrate with enhanced bias stability. Compared with parylene‐C passivation, the hybrid‐passivated IGZO TFTs exhibit excellent saturation mobility (7.9 cm2 (V s)−1), ON/OFF ratio (107), hysteresis window (0.73 V), and bias stability (1.44 and −0.27 V threshold voltage shift, Vds = 20 V). Based on systematic Mott–Schottky and X‐ray diffraction characterizations, it is found that TFT performance enhancement is originated from their doping density variation that resulted from a parylene‐C/ALD‐AlOx microstructural hybridization. Finally, this method is implemented to wafer‐scale integrated circuits with high uniformity and a flexible 10 × 10 IGZO TFT backplane matrix on a PEN substrate (2.5 cm × 2.5 cm)

Lattice marginal reconstruction enabled high ambient-tolerance Perovskite Quantum Dots phototransistors

Perovskite quantum dots (PeQDs) have been developed rapidly as photoactive materials in hybrid phototransistors because of their strong light absorption, broad bandgap customizability, and defect-tolerance in charge-transport properties. The solvent treatment has been well recognized as a practical approach for improving the charge transport of PeQDs and the photoresponsivity of PeQD phototransistors. However, there is a lack of fundamental understanding of the origin of its impacts on the material’s ambient stability as well as phototransistor’s operational lifetime. Especially, the relationship between surface ligands dissociation and their microstructural reconstruction has not been fully elucidated so far. Herein, we report that a simultaneous enhancement of photoresponsivity and ambient tolerance for PeQD-based hybrid phototransistors can be realized via medium-polarity-solvent treatment on solid-state PeQDs. Our comprehensive optoelectronic characterization and electron microscopic study reveals that the crystal morphology, instead of surface ligands, is the dominating factor that results in the PeQD’s stability enhancement associated with the preservation of optical property and quantum confinement. Besides, we unveil a marginal reconstruction process occurred during solvent treatment, which opens up a new route for facets-oriented attachment of PeQDs along the zone axis to suppress the damage from water molecules penetration. Our study yields a new understanding of the solvent impact on PeQD microstructures reconstruction and suggests new routes for perovskite materials and corresponding device operational stability enhancement

A novel molecular signature for predicting prognosis and immunotherapy response in osteosarcoma based on tumor-infiltrating cell marker genes

BackgroundTumor infiltrating lymphocytes (TILs), the main component in the tumor microenvironment, play a critical role in the antitumor immune response. Few studies have developed a prognostic model based on TILs in osteosarcoma.MethodsScRNA-seq data was obtained from our previous research and bulk RNA transcriptome data was from TARGET database. WGCNA was used to obtain the immune-related gene modules. Subsequently, we applied LASSO regression analysis and SVM algorithm to construct a prognostic model based on TILs marker genes. What’s more, the prognostic model was verified by external datasets and experiment in vitro. ResultsEleven cell clusters and 2044 TILs marker genes were identified. WGCNA results showed that 545 TILs marker genes were the most strongly related with immune. Subsequently, a risk model including 5 genes was developed. We found that the survival rate was higher in the low-risk group and the risk model could be used as an independent prognostic factor. Meanwhile, high-risk patients had a lower abundance of immune cell infiltration and many immune checkpoint genes were highly expressed in the low-risk group. The prognostic model was also demonstrated to be a good predictive capacity in external datasets. The result of RT-qPCR indicated that these 5 genes have differential expression which accorded with the predicting outcomes.ConclusionsThis study developed a new molecular signature based on TILs marker genes, which is very effective in predicting OS prognosis and immunotherapy response

Lattice Marginal Reconstruction Enabled High Ambient-Tolerance Perovskite Quantum Dots Phototransistors

Perovskite quantum dots (PeQDs) have been developed rapidly as photoactive materials in hybrid phototransistors because of their strong light absorption, broad bandgap customizability, and defect-tolerance in charge-transport properties. The solvent...</p

Modelling charge transport and electro-optical characteristics of quantum dot light-emitting diodes

Abstracts: Quantum dot light-emitting diodes (QD-LEDs) are considered as competitive candidate for next-generation displays or lightings. Recent advances in the synthesis of core/shell quantum dots (QDs) and tailoring procedures for achieving their high quantum yield have facilitated the emergence of high-performance QD-LEDs. Meanwhile, the charge-carrier dynamics in QD-LED devices, which constitutes the remaining core research area for further improvement of QD-LEDs, is, however, poorly understood yet. Here, we propose a charge transport model in which the charge-carrier dynamics in QD-LEDs are comprehensively described by computer simulations. The charge-carrier injection is modelled by the carrier-capturing process, while the effect of electric fields at their interfaces is considered. The simulated electro-optical characteristics of QD-LEDs, such as the luminance, current density and external quantum efficiency (EQE) curves with varying voltages, show excellent agreement with experiments. Therefore, our computational method proposed here provides a useful means for designing and optimising high-performance QD-LED devices