Zeolitic Imidazole Framework as Defect Passivation Layer for Enhanced Electron Injection Efficiency in Organic Light‐Emitting Diodes

Understanding and controlling interfacial chemistry remains a critical challenge in optoelectronic materials. This study demonstrates that incorporating a zeolitic imidazolate framework-8 (ZIF-8) can be succesfully integrated as a coordination-driven passivation layer in inverted organic light-emitting diodes (iOLEDs). The ZIF-8 layer is in situ formed on ZnO films via a solution-based heterogeneous nucleation process to yield a ZnO:ZIF-8 composite electron-transporting layer (ETL). Spectroscopic and electrochemical analyses confirm that Zn-N coordination at the interface effectively passivates oxygen vacancies, suppresses electron trapping, and reduces non-radiative recombination. The incorporation of ZIF-8 also modifies the surface potential of ZnO for better energy level alignment to the adjacent organic emissive layer and lowers the electron injection barrier. Devices incorporating the ZnO:ZIF-8 ETL achieve a maximum luminance of 17800 cd m^-2 with significantly enhanced operational stability under high voltages. The work establishes a MOF-based interfacial coordination strategy to address charge transport limitations in optoelectronic devices and expands the use of MOFs in advanced optoelectronic applications.