Solution-processed highly bright and durable cesium lead halide perovskite light-emitting diodes.

Recently, CsPbBr perovskites have been emerging as very promising green emission materials for light-emitting diodes (LEDs) due to their high color purity, low cost and high photoluminescence quantum yield (PLQY). However, the corresponding LED performance is still low and far behind CHNHPbBr; it is due to the lack of proper perovskite film preparation methods and interfacial engineering. Herein, we report highly bright and durable CsPbBr-based LEDs fabricated using a one-step solution method. The precursor solution is prepared by simply dissolving CsPbBr powder and a CsBr additive in dimethyl sulfoxide (DMSO). We find that the CsBr additive not only significantly enhances the PLQY but also induces directional crystal growth into micro-plates, forming a smooth perovskite film for LEDs. LEDs employing such high quality films show a high luminance of 7276 cd m and high color purity with a full width at half maximum of 18 nm. Furthermore, the as-fabricated LEDs reveal an outstanding ambient stability with a decent luminance output (>100 cd m, steady increase without any degradation trend) for at least 15 h under a constant driving current density (66.7 mA cm). And we propose two reasons for this unique luminance increasing behavior: (1) the CsPbBr perovskite is thermally stable and can survive from joule heat; and (2) on the other hand, the joule heating will induce interface or crystalline film annealing, reduce device resistance and then enhance the luminance output.