Stable and reliable IGZO resistive switching device with HfAlOxinterfacial layer.

The performance stability of the resistive switching (RS) is vital for a resistive random-access memory device. Here, by inserting a thin HfAlOxlayer between the InGaZnO (IGZO) layer and the bottom Pt electrode, the RS performance in amorphous IGZO memory device is significantly improved. Comparing with a typical metal-insulator-metal structure, the device with HfAlOxlayer exhibits lower switching voltages, faster switching speeds, lower switching energy and lower power consumption. As well, the uniformity of switching voltage and resistance state is also improved. Furthermore, the device with HfAlOxlayer exhibits long retention time (>104s at 85 °C) , high on/off ratio and more than 103cycles of endurance at atmospheric environment. Those substantial improvements in IGZO memory device are attributed to the interface effects with a HfAlOxinsertion layer. With such layer, the formation and rupture locations of Ag conductive filaments are better regulated and confined, thus an improved performance stability.

Meniscus-Guided 3D Microprinting of Pure Metal-Organic Frameworks with High Gas-Uptake Performance.

Metal-organic frameworks (MOFs) are a promising nanoporous functional material system; however, the practicality of shaping freeform MOF monoliths, while retaining their porosity, remains a challenge. Here, we demonstrate that meniscus-guided three-dimensional (3D) printing can produce pure MOF monoliths with high gas-uptake performance. The method exploits a femtoliter precursor ink meniscus to highly confine and guide supersaturation-driven crystallization in a layer-by-layer manner to print a pure HKUST-1 micro-monolith with a high spatial resolution of <3 µm. The proposed 3D printing technique does not involve rheological additives, binders, or mechanical forces. Thus, the resulting HKUST-1 monolith displays a prominently high Brunauer-Emmett-Teller surface area of 1192 m2/g, which is superior to monoliths produced using other 3D printing approaches. This technique enables both structural design freedom and high material performance in the manufacturing of MOFs for practical use.

Efficient quantum dot light-emitting diodes with a Zn0.85Mg0.15O interfacial modification layer.

Efficient inverted quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated by using 15% Mg doped ZnO (Zn0.85Mg0.15O) as an interfacial modification layer. By doping Mg into ZnO, the conduction band level, the density of oxygen vacancies and the conductivity of the ZnO can be tuned. To suppress excess electron injection, a 13 nm Zn0.85Mg0.15O interlayer with a relatively higher conduction band edge and lower conductivity is inserted between the ZnO electron transport layer and QD light-emitting layer, which improves the balance of charge injection and blocks the non-radiative pathway. Moreover, according to the electrical and optical studies of devices and materials, quenching sites at the ZnO surface are effectively reduced by Mg-doping. Therefore exciton quenching induced by ZnO nanoparticles is largely suppressed by capping ZnO with Zn0.85Mg0.15O. Consequently, the red QLEDs with a Zn0.85Mg0.15O interfacial modification layer exhibit superior performance with a maximum current efficiency of 18.69 cd A-1 and a peak external quantum efficiency of 13.57%, which are about 1.72- and 1.74-fold higher than 10.88 cd A-1 and 7.81% of the devices without Zn0.85Mg0.15O. Similar improvements are also achieved in green QLEDs. Our results indicate that Zn0.85Mg0.15O can serve as an effective interfacial modification layer for suppressing exciton quenching and improving the charge balance of the devices.

Efficient vacuum-free-processed quantum dot light-emitting diodes with printable liquid metal cathodes.

Colloidal quantum dot light-emitting diodes (QLEDs) are recognized as promising candidates for next generation displays. QLEDs can be fabricated by low-cost solution processing except for the metal electrodes, which, in general, are deposited by costly vacuum evaporation. To be fully compatible with the low-cost solution process, we herein demonstrate vacuum-free and solvent-free fabrication of electrodes using a printable liquid metal. With eutectic gallium-indium (EGaIn) based liquid metal cathodes, vacuum-free-processed QLEDs are demonstrated with superior external quantum efficiencies of 11.51%, 12.85% and 5.03% for red, green and blue devices, respectively, which are about 2-, 1.5- and 1.1-fold higher than those of the devices with thermally evaporated Al cathodes. The improved performance is attributable to the reduction of electron injection by the native oxide of EGaIn, which serves as an electron-blocking layer for the devices and thus improves the balance of carrier injection. Also, the T50 half-lifetime of the vacuum-free-processed QLEDs is about 2-fold longer than that of the devices with Al cathodes. Our results demonstrate that EGaIn-based solvent-free liquid metals are promising printable electrodes for realizing efficient, low-cost and vacuum-free-processed QLEDs. The elimination of vacuum and high-temperature processes significantly reduces the production cost and paves the way for industrial roll-to-roll manufacturing of large area displays.

Improving Electron Mobility of Tetraphenylethene-Based AIEgens to Fabricate Nondoped Organic Light-Emitting Diodes with Remarkably High Luminance and Efficiency.

Robust light-emitting materials with strong solid-state fluorescence as well as fast and balanced carrier transporting ability are crucial to achieve high-performance organic light-emitting diodes (OLEDs). In this contribution, two linear tetraphenylethene (TPE) derivatives (TPE-TPAPBI and TPE-DPBI) that are functionalized with hole-transporting triphenylamine and/or electron-transporting 1,2-diphenyl-1H-benzimidazole groups are synthesized and fully characterized. Both TPE-TPAPBI and TPE-DPBI have aggregation-induced emission attributes and excellent photoluminescence quantum yields approaching 100% in vacuum deposited films. They also possess good thermal property, giving high decomposition temperatures (480 and 483 °C) and glass-transition temperatures (141 and 157 °C). TPE-TPAPBI and TPE-DPBI present high electron mobilities of 1.80 × 10(-5) and 1.30 × 10(-4) cm(2) V (-1) s(-1), respectively, at an electric field of 3.6 × 10(5) V cm(-1), which are comparable or even superior to that of 1,3,5-tri(1-phenylbenzimidazol-2-yl)benzene. The nondoped OLED device employing TPE-TPAPBI as active layer performs outstandingly, affording ultrahigh luminance of 125 300 cd m(-2), and excellent maximum external quantum, power and current efficiencies of 5.8%, 14.6 lm W(-1), and 16.8 cd A(-1), respectively, with very small roll-offs, demonstrating that TPE-TPAPBI is a highly promising luminescent material for nondoped OLEDs.