ABSTRACT: Here a high-brightness perovskite microcrystalline light-emitting diode (LED)is reported, in which the perovskite microcrystals were grown directly on the conductivesubstrate and a simple metal−insulator−semiconductor structure was adopted. A peak externalquantum effiffifficiency of 0.46% was obtained, which is high for perovskite microcrystalline LEDs.Importantly, the maximum luminance of the device reaches 8848.4 cd m−2 , indicating anultrahigh brightness of >1.2 × 106 cd m−2 for the microcrystals (corresponding to an ultrahighcurrent density of 80.9 A cm−2 ), because the light-emitting area of the microcrystals accountsfor only ∼0.7% of the device area. In addition, we have studied the degradation of the device ata high current density by in situ microscopic observation and found that a severe Joule heatingeffffect at large injection is the primary problem to be solved to realize electrically pumpedperovskite microcrystal lasing
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