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The effects of the parasitic gate capacitance and gate resistance (Rg) on the radiofrequency (RF) performance are investigated in LG = 0.15 μm GaN high‐electron‐mobility transistors with T‐gate head size ranging from 0.83 to 1.08 μm. When the device characteristics are compared, the difference in DC characteristics is negligible. The RF performance in terms of the current‐gain cut‐off frequency (fT) and maximum oscillation frequency (fmax) substantially depend on the T‐gate head size. For clarifying the T‐gate head size dependence, small‐signal modeling is conducted to extract the parasitic gate capacitance and Rg. When the T‐gate head size is reduced from 1.08 to 0.83 μm, Rg increases by 82%, while fT and fmax improve by 27% and 26%, respectively, because the parasitic gate–source and gate–drain capacitances reduce by 19% and 43%, respectively. Therefore, minimizing the parasitic gate capacitance is more effective that reducing Rg in our transistor design and fabrication, leading to improved RF performance when reducing the T‐gate head size. [ABSTRACT FROM AUTHOR]

Various high boiling point solvent additives are commonly used for high-performing organic solar cells (OSCs). However, they are not only usually detrimental to device stability but also often contain halogens, rendering them highly reactive and environmentally unfriendly. Herein, a non-halogenated and non-volatile solid additive, 2-(4-phenoxybenzylidene)-1H-indene-1,3(2H)-dione (PID), is synthesized for the preparation of high-performing and highly stable non-fullerene acceptor (NFA)-based OSCs. PID introduction enhances the molecular ordering of the photoactive materials and optimizes their nanoscale phase-separated morphology by controlling intermolecular interactions. The power conversion efficiency (PCE) of the resulting PID-processed OSC devices increases from 13.9% to 16.3%, surpassing that of 1-chloronaphthalene (CN)-processed devices (15.5%). Moreover, when burn-in losses are eliminated, the PID-processed devices demonstrate excellent thermal stability, retaining 98% of their initial PCE after 1200 h at 85 °C. Such high thermal stability renders these devices among the most stable PM6:Y6-based OSCs reported to date. The results suggest that non-volatile solid additives can simultaneously enhance the efficiency and stability of OSC devices without halogens, thereby opening up possibilities for their future commercial applications. [ABSTRACT FROM AUTHOR]

To realize the commercialization of nonfullerene acceptor‐based efficient organic solar cells, a low‐cost and indium‐tin‐oxide‐free (ITO‐free) flexible electrode‐based module that can be produced by roll‐to‐roll production should be developed. However, the low surface energy of ITO‐free electrodes hinders the formation of a uniform charge transport layer through solution processing; this is the main cause of the efficiency drop. Herein, the realization of a highly uniform ZnO bilayer on an ultrathin Ag film‐based transparent electrode that is suitable for flexible substrates and large‐area organic photovoltaic (OPV) module fabrication is demonstrated. Based on the sputtered ZnO and blade‐coated ZnO nanoparticle‐based electron transport bilayer, large OPV module areas of 528.5 and 108 cm2 with high efficiencies of 7.67% and 9.15%, respectively, are achieved. [ABSTRACT FROM AUTHOR]

Hollow and nanoparticulate Au/CeO2 (Au/HN-CeO2) catalysts were synthesized using hollow microporous organic polymers as templates and applied for the controlled oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to polymer building blocks, 5-hydroxymethylfuran-2-carboxylic acid (HMFC) and furan-2,5-dicarboxylic acid (FDC). The optimal amounts of Au in Au/HN-CeO2 catalysts resulted in the selective formation of HMFC and FDC with excellent yields of up to 93–96%. The Au-amount-dependent catalytic performance resulted from the cluster and nanoparticle features of Au species in Au/HN-CeO2 catalysts. Au/HN-CeO2 could be recycled in five successive oxidation reactions of HMF to HMFC, maintaining the original catalytic performance. [ABSTRACT FROM AUTHOR]

We numerically demonstrated switchable metasurfaces using a phase change material, VO 2 by temperature change. The Pancharatnam–Berry metasurface was realized by using an array of Au nanorods on top of a thin VO 2 film above an Au film, where the optical property of the VO 2 film is switched from the insulator phase at low temperature to the metal phase at high temperature. At the optimal structure, polarization conversion efficiency of the normal incident light is about 75% at low temperature while that is less than 0.5% at high temperature in the visible region ( λ ∼ 700 nm). Various functionalities of switchable metasurfaces were demonstrated such as polarization conversion, beam steering, Fourier hologram, and Fresnel hologram. The thin-VO 2 -film-based switchable metasurface can be a good candidate for various switchable metasurface devices, for example, temperature dependent optical sensors, beamforming antennas, and display. [ABSTRACT FROM AUTHOR]

To realize the commercialization of nonfullerene acceptor‐based efficient organic solar cells, a low‐cost and indium‐tin‐oxide‐free (ITO‐free) flexible electrode‐based module that can be produced by roll‐to‐roll production should be developed. However, the low surface energy of ITO‐free electrodes hinders the formation of a uniform charge transport layer through solution processing; this is the main cause of the efficiency drop. Herein, the realization of a highly uniform ZnO bilayer on an ultrathin Ag film‐based transparent electrode that is suitable for flexible substrates and large‐area organic photovoltaic (OPV) module fabrication is demonstrated. Based on the sputtered ZnO and blade‐coated ZnO nanoparticle‐based electron transport bilayer, large OPV module areas of 528.5 and 108 cm2 with high efficiencies of 7.67% and 9.15%, respectively, are achieved. [ABSTRACT FROM AUTHOR]

A microporous organic polymer (MOP) was utilized for the engineering of nanoparticulate CeO 2 in a hollow carbon matrix (H-C/CeO 2 ). After CeO 2 nanoparticles were incorporated into a hollow MOP platform (H-MOP) through the decomposition of cerium acetate, successive carbonization produced H-C/CeO 2 . The redox feature of defective CeO 2 in a conductive carbon matrix induced promising pseudocapacitive behavior. In particular, the H-C/CeO 2 showed excellent electrochemical performance in an alkaline electrolyte (KOH), due to the hydroxide ion-assisted redox behavior of defective CeO 2 . H-C/CeO 2 -3 with an optimized amount of CeO 2 showed specific capacitances of up to 527 (@0.5 A g -1 ) and 493 F g -1 (@1 A g -1 ). Even at high current densities of 10 and 20 A g -1 , the H-C/CeO 2 -3 maintained high capacitances of 458 and 440 F g -1 , respectively. After 10 000 cycling tests, the H-C/CeO 2 -3 retained the 94-95% capacitance of the first cycle.