Highly bright light-emitting diodes based on solution-processed all-inorganic perovskite thin film are demonstrated. The cesium lead bromide (CsPbBr ) created using a new poly(ethylene oxide)-additive spin-coating method exhibits photoluminescence quantum yield up to 60% and excellent uniformity of electrical current distribution. Using the smooth CsPbBr films as emitting layers, green perovskite-based light-emitting diodes (PeLEDs) exhibit electroluminescent brightness and efficiency above 53 000 cd m and 4%: a new benchmark of device performance for all-inorganic PeLEDs.

Organic-inorganic hybrid perovskites have shown great potential as building blocks for low-cost optoelectronics for their exceptional optical and electrical properties. Despite the remarkable progress in device demonstration, fundamental understanding of the physical processes in halide perovskites remains limited, especially the unusual electronic behaviors such as the current-voltage hysteresis and the switchable photovoltaic effect. These phenomena are of particular interests for being closely related to device functionalities and performance. In this work, a microscopic picture of electric fields in halide perovskite thin films was obtained using scanning laser microscopy. Unlike conventional semiconductors, distribution of the built-in electric fields in the halide perovskite evolves dynamically under the stimulation of external biases. The observations can be well explained using a model based on field-assisted ion migration, indicating that the mechanism responsible for the evolving charge transport observed in this material is not purely electronic. The anomalous dynamic responses to the applied bias are found to be effectively suppressed by operating the devices at reduced temperature or processing the materials at elevated temperature, which provide potential strategies for designing and creating halide perovskites with more stable charge transport properties in the development of viable perovskite-based optoelectronics.

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By specifying objective functions defining the two bands to be notched with high roll‐off criteria (ROCs), optimization searching for the best fragment‐type etch pattern on ultra‐wideband (UWB) antenna is implemented by using multi‐objective optimization. The optimization with too many objective functions requires special treatment to improve the searching efficiency. In this design, two slits are preset on appropriate positions on different sides of the UWB radiator to constrain the decision space for etch pattern searching and yield two initial notched bands to speed up the optimization. For demonstration, a UWB patch antenna is designed with dual‐band notches of ROC = 0.63 at WiMAX band and ROC = 0.65 at WLAN band. Both the simulation and measurement results indicate that there is significant improvement of the selectivity of the dual‐band notches.