Perovskite Light Emitting Diodes Based on Zinc Oxide Electron Transport Layers: Recent Advances and Challenges

Zinc oxide (ZnO) electron transport layers (ETLs) have been widely used in solution-processed light-emitting diodes (LEDs) due to their high electron mobility, thermal stability, and low cost. Recently, integrating ZnO ETLs with perovskite emitters, known for their high defect tolerance, tunable emission wavelengths, and high color purity, has garnered significant attention as candidates for next-generation LEDs. This integration has recently demonstrated excellent near-infrared perovskite LEDs (PeLEDs) but has not yet succeeded in three-primary-color PeLEDs. This review summarizes recent advancements and challenges in PeLEDs based on ZnO ETLs, aiming to provide a roadmap for future development of high-performance PeLEDs for high definition displays. The fabrication processes of ZnO ETL-based PeLEDs, focusing on the compatibility of ZnO ETLs and perovskite emitters deposition techniques, are thoroughly discussed. Particular attention is given to the interfacial interactions between ZnO ETLs and perovskite emitters, as well as the optimization strategies. Additionally, recent advances in the performance of ZnO ETL-based PeLEDs including near-infrared, red, green, and blue emissions are systematically summerized and the specific requirements for enhancing performance of PeLEDs at each color are clearly presented. Finally, an outlook on promising research directions to improve the performance of ZnO ETL-based PeLEDs is provided.