Improved Charge Balance in Green Perovskite Light-Emitting Diodes with Atomic-Layer-Deposited Al 2 O 3 .

Perovskite light-emitting diodes (LEDs) have experienced a rapid increase in efficiency over the last several years and are now regarded as promising low-cost devices for displays and communication systems. However, it is often challenging to employ ZnO, a well-studied electron transport material, in perovskite LEDs due to chemical instability at the ZnO/perovskite interface and charge injection imbalance caused by the relatively high conductivity of ZnO. In this work, we address these problems by depositing an ultrathin Al 2 O 3 interlayer at the ZnO/perovskite interface, allowing the fabrication of green-emitting perovskite LEDs with a maximum luminance of 21 815 cd/m 2 . Using atomic layer deposition, we can precisely control the Al 2 O 3 thickness and thus fine-tune the electron injection from ZnO, allowing us to enhance the efficiency and operational stability of our LEDs.