presence of aliphatic ligands. [ 7 ] These perovskite nanocrystals are highly luminescent and emit over the full visible range, making them ideal candidates for luminescent display applications. [ 6 ] The synthetic steps are generally straightforward, and the easy control of halide content allows the perovskite bandgaps to be tailored, both by chemical compositions as well as by quantum size effects. So far, perovskite nanocrystals are shown to have color-pure emission, close to unity photoluminescence yield and low lasing thresholds. [ 8 ] These nanocrystals were also attempted in light-emitting devices, but effi ciencies remain modest at 0.12%. [ 9 ] Here, we show the preparation of highly effi cient perovskite light-emitting diodes (PeLED) using solution-processed nanocrystals. We apply a new trimethylaluminum (TMA) vapor-based crosslinking method to render the nanocrystal fi lms insoluble, thereby allowing the deposition of subsequent charge-injection layers without the need for orthogonal solvents. The resulting near-complete nanocrystal fi lm coverage, coupled with the natural confi nement of injected charges within the perovskite crystals, facilitate electron-hole capture and give rise to a remarkable electroluminescence yield of 5.7%. Here, our electron-injection layer comprises a fi lm of zinc oxide (ZnO) nanocrystals, directly deposited on an indium tin oxide (ITO)-coated glass substrate. [ 4 ] The cesium lead halide nanocrystals were solution-coated onto the ZnO fi lm as the emissive layer. Due to the presence of aliphatic ligands on the nanocrystals, the perovskite fi lm remains soluble to organic solvents, which limits the deposition of subsequent chargeinjection layers using solution methods. We employed a new TMA vapor-phase crosslinking technique to fi x the nanocrystal fi lm in place, thereby enabling us to solution-cast a layer of TFB polymer (poly[(9,9-dioctylfl uorenyl-2,7-diyl)-co -(4,4′-( N -(4-sec-butylphenyl)diphenylamine)]) above without washing the nanocrystals off. TFB serves primarily as a hole-injection and electron-blocking layer. A thin, high work-function molybdenum trioxide (MoO 3 ) interlayer and silver electrode were vacuum-thermal evaporated to complete the device.As shown in Figure 1 c,d, our perovskite nanocrystal devices show saturated and color-pure emission. We control the perovskite bandgap, primarily by tailoring the halide composition, and achieve electroluminescence across a wide range of the visi ble spectrum. Our red, orange, green, and blue devices emit at wavelengths of 698, 619, 523, and 480 nm, respectively.

A novel type of flexible fiber/wearable supercapacitor that is composed of two fiber electrodes - a helical spacer wire and an electrolyte - is demonstrated. In the carbon-based fiber supercapacitor (FSC), which has high capacitance performance, commercial pen ink is directly utilized as the electrochemical material. FSCs have potential benefits in the pursuit of low-cost, large-scale, and efficient flexible/wearable energy storage systems.

For modern color-rendering applications, efficient blue, green, and red LEDs are required. While efficient green and red perovskite LEDs have been demonstrated, blue devices lag significantly behind due to the poor quality of chloride-based perovskites. Here, we show that doping manganese into blue perovskite nanocrystals increases their brightness and efficiency. By putting doped nanocrystals into LEDs, we see a 4-fold increase in efficiency, demonstrating that blue LEDs can be as efficient as their red and green cousins.

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