Aqueous solution processed transition-metal-doped ZnO as electron injection layers for efficient inverted organic light emitting diodes

• Published in: Synthetic metals 2024-07, Vol.305, p.117595, Article 117595
• Main Authors: Li, Yaozhao, Li, Peng, Zhang, Pengpeng, Wei, Bin, Chen, Guo
• Format: Article
• Language: English
• Subjects: Electron injection; Inverted structure; OLED; Solution process; Transition-metal-doped ZnO
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/j.synthmet.2024.117595

Zinc oxide (ZnO) has attracted lots of attention to be used as interfacial materials in organic optoelectronic devices owing to its attractive properties. In this work, a series of transition-metal-doped ZnO thin films were prepared by using a facile aqueous solution process, thereafter these films were employed as electron injection layers (EILs) combined with the tris-(8-hydroxyquinoline) aluminum (Alq3) emitting layer to construct the inverted organic light-emitting diodes (IOLEDs). The transition-metal-doped ZnO EIL-based IOLEDs demonstrate markedly improved device performance compared to the reference neat ZnO EIL-based IOLED. However, different transition-metal ions have much different doping effect on the device performance. CoCl2 doped ZnO EIL based IOLED device possesss an optimal current efficiency of 5.52 cd A−1, which is increased about 40% compared to the device with the neat ZnO as EIL. The enhancement might be attributed to the increased electron mobility and favorable interfacial energy level alignment of the transition-metal doped ZnO EIL for more efficient electron injection. Our findings may provide a promising strategy to improve the electron injection properties of ZnO film in the OLED devices. •The transition-metal-doped ZnO films were used as the electron injection layers in OLEDs.•Transition-metal-doped ZnO films were prepared by using a facile aqueous solution process.•The transition-metal doping increased the electron injection efficiency of the OLEDs.