Intragrain 3D perovskite heterostructure for high-performance pure-red perovskite LEDs.

Metal-halide perovskites are promising light-emitter candidates for next-generation light-emitting diodes (LEDs). Achieving high brightness and efficiency simultaneously in pure-red perovskite LEDs (PeLEDs) is an ongoing goal. Three-dimensional (3D) CsPbIBr emitters have excellent carrier transport capability and high colour purity, which could allow efficient and ultrabright pure-red PeLEDs. However, such devices are prone to efficiency roll-off, resulting in low efficiency and low brightness under high current density. Here, by using electrically excited transient absorption spectroscopy, we discovered the efficiency roll-off was induced by hole leakage. Therefore, we developed a CsPbIBr intragrain heterostructure containing narrow bandgap emitters and wide bandgap barriers to confine the injected carriers. The wide bandgap barrier was incorporated by introducing strongly bonding molecules into the [PbX] framework to expand the 3D CsPbIBr lattice. This strategy resulted in bright and efficient pure-red PeLEDs, with a high brightness of 24,600 cd m, maximum external quantum efficiency of 24.2% and low efficiency roll-off, maintaining a 10.5% external quantum efficiency at a high luminance of 22,670 cd m.