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The influence of H2O and O2 on the performances of Mg-doped zinc oxide (ZnMgO) and ZnMgO-based inverted quantum-dot light-emitting diodes (QLEDs) are studied. With the involvement of H2O from ambience, ZnMgO exhibits a high conductivity, whereas the resultant QLEDs show a low efficiency. The efficiency of QLEDs can be enhanced by annealing ZnMgO in H2O-free glovebox; however, the uniformity and the current of the devices are degraded due to the presence of O2, which adsorbs on the surface of ZnMgO and captures the free electrons of ZnMgO. By exposing the devices with ultraviolet (UV) irradiation, the adsorbed O2 can be released, consequently leading to the increase of driving current. Our work discloses the influence of the annealing ambience on the conductivity of ZnMgO, and reveals the interaction of H2O/O2 and UV with the ZnMgO and its effect on the performance of the resultant inverted QLEDs, which could help the community to better understand the mechanisms of ZnMgO-based QLEDs. [ABSTRACT FROM AUTHOR]

Liquid metals based on eutectic gallium–indium (EGaIn) alloys are promising printable electrode materials for various printed devices such as light-emitting diodes or solar cells. To achieve a controllable and fine patterning of the EGaIn electrodes, herein, a facile bottom-up, additive technique has been developed by manipulating wetting/dewetting of the substrate. The substrate is first dewetted by coating a hydrophobic layer; then, to selectively dewet the substrate, the coated hydrophobic layer is patterned by laser ablation. EGaIn, which is painted onto the substrate, can only adhere to the wetting regions and thus can perfectly copy the patterns of the wetting regions. Via this method, high-resolution EGaIn patterns with a line width smaller than 100 μm can be obtained. Using the patterned EGaIn electrodes, all-printed quantum dot light-emitting diodes were successfully demonstrated. The proposed method offers a feasible route for fast patterning of EGaIn and thus allows for inexpensive, rapid fabrication of various devices without the need of costly vacuum processing. [ABSTRACT FROM AUTHOR]

We demonstrate a rechargeable zinc-ion battery with high energy density and cyclability using MnO2 and reduced graphene oxide (MnO2/rGO) electrode. The flexible and binder free electrode, with high MnO2 mass ratio (80 wt% of MnO2), is fabricated using vacuum filtration without any additional additives other than rGO. Compared to batteries with conventional MnO2 electrodes, the Zn–MnO2/rGO battery shows a significant enhanced capacity (332.2 mAh g-1 at 0.3 A g-1), improved rate capability (172.3 mAh g-1 at 6 A g-1) and cyclability. The capacity retention remains 96% after 500 charge/discharge cycles at 6 A g-1. The high MnO2 mass ratio makes MnO2/rGO electrode advantageous when the capacity is normalized to the whole electrode, particularly at high rates. The calculated gravimetric energy density of Zn–MnO2/rGO battery is 33.17 W h kg-1, which is comparable to the existing commercial lead-acid batteries (30–40 W h kg-1). Furthermore, the discharge profile and capacity of our Zn–MnO2/rGO battery shows no deterioration during bending test, indicating good flexibility. As a result, zinc-ion battery is believed to be a promising technology for powering next generation flexible electronics. Zinc-ion batteries: a carbon based promoter Simple carbon materials are shown to modify the MnO2 electrodes and greatly enhance the capacity and cyclability for zinc-ion batteries. An international team led by Prof Hang Zhou from Peking University Shenzhen Graduate School, China developed high performance flexible zinc-ion batteries with MnO2 and reduced graphene-oxide composites as the electrodes. The electrodes are prepared by vacuum filtering the suspension of the mixture of reduced graphene oxide and hydrothermal synthesized MnO2 nanosheets. The incorporation of reduced graphene oxide not only enhances the battery capacity by improving the conductivity and increasing the specific surface area, but also reduces the production cost by saving the trouble to use other binders or additives. Due to above advantages, this approach is competitive for wearable energy storage devices. [ABSTRACT FROM AUTHOR]