“…Metal halide perovskites have won great recognition in light-emitting diodes (LEDs), owning to their fascinating optical and electronic properties, such as easily tunable bandgap, high charge mobility, low exciton binding energy, high defect tolerance, and low-cost solution processability. − Since the first perovskite LED (PeLED) was fabricated in 2014, external quantum efficiency (EQE) has exceeded 20% for green, − red, − and near-infrared , PeLEDs respectively, enabling them to be competitive with prevalent organic and quantum-dot LEDs . In contrast, the development of blue PeLEDs is facing a bottleneck in improving the device efficiency and stability. − …”