We demonstrate a rechargeable zinc-ion battery with high energy density and cyclability using MnO 2 and reduced graphene oxide (MnO 2 /rGO) electrode. The flexible and binder free electrode, with high MnO 2 mass ratio (80 wt% of MnO 2), is fabricated using vacuum filtration without any additional additives other than rGO. Compared to batteries with conventional MnO 2 electrodes, the Zn-MnO 2 /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 MnO 2 mass ratio makes MnO 2 /rGO electrode advantageous when the capacity is normalized to the whole electrode, particularly at high rates. The calculated gravimetric energy density of Zn-MnO 2 /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-MnO 2 /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.

Five deep blue carbene-based iridium(III) phosphors were synthesized and characterized. Interestingly, one of them can be fabricated into deep blue, sky blue and white organic light-emitting diodes (OLEDs) through changing the host materials and exciton blocking layers. These deep and sky blue devices exhibit Commission Internationale de l'Éclairage (CIE) coordinates of (0.145, 0.186) and (0.152, 0.277) with external quantum efficiency (EQE) of 15.2% and 9.6%, respectively. The EQE of the deep blue device can be further improved up to 19.0% by choosing a host with suitable energy level of its lowest unoccupied molecular orbital (LUMO).

EGaIn liquid metal electrodes have been fine patterned by manipulating wetting/dewetting of the substrate for all-printed device application.

The performance of the blue quantum dot light‐emitting diodes (QLEDs) is largely affected by the hole transport layers (HTLs). As a consequence of the deep valance band level of blue quantum dots (QDs), hole injection is relatively difficult in blue QLEDs. To favor the hole injection, HTLs with high hole mobility and deep‐lying highest occupied molecular orbital level are desired. In this work, various HTLs and their influence on the performance of blue QLEDs are demonstrated. Devices with poly(N‐vinylcarbazole) (PVK) HTL exhibit the highest external quantum efficiency while devices with poly[9,9‐dioctylfluorene‐co‐N‐(4‐(3‐methylpropyl))‐diphenylamine] (TFB) exhibit the lowest driving voltage. By combining the advantages of PVK and TFB, the blue QLEDs with TFB/PVK bilayered HTL simultaneously exhibit a low driving voltage of 2.6 V and a high external quantum efficiency of 5.9%. Moreover, the exciplex emission at the interface of HTL/QDs is also observed, and the emission intensity can be tuned by modulating the hole injection. By utilizing PVK doped with 25% poly(3‐hexylthiophene) (P3HT) as HTL, exciplex emission is significantly enhanced at low driving voltage while QD emission is dominant at high driving voltage. By combining the exciplex emission and the QD emission, the emission color can be effectively tuned from red to blue as the driving voltage changing from 2 to 10 V.

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