Multiple-quantum-well perovskite for hole-transport-layer-free light-emitting diodes

We demonstrate hole-transport-layer-free light-emitting diodes (LEDs) based on solution-processed multiple-quantum-well (MQW) perovskite. The MQW perovskite can self-assemble to a unique structure of vertically graded distribution with two-dimensional layered perovskite covered by three-dimensional-like perovskite at top, which can naturally form a barrier of electron transporting to the anode interface, thereby enhancing the charge capture efficiency. This leads to hole-transport-layer-free MQW perovskite LEDs reaching an external quantum efficiency (EQE) of 9.0% with emission peak at 528 nm, which is over 6 times of LEDs based on three-dimensional perovskite with the same device structure, representing the record EQE of hole-transport-layer-free perovskite LED.