Phenanthroline‐Modified Electrodes for Suppressing Moisture‐Induced Degradation in Nonencapsulated Organic Light‐Emitting Diodes

Electron injection stability is crucial for organic semiconductors. Although phenanthroline (Phen) derivatives are stable and efficient electrode modification materials, their air stability is underexplored, and the impacts of environmental factors on Phen‐modified electrodes are not well understood. This study investigates the degradation of Phen‐modified organic light‐emitting diodes (OLEDs) by monitoring temporal changes in the light‐emitting area under ambient air exposure without encapsulation. The results demonstrate that Phen modification stabilizes electron injection under room‐temperature and atmospheric‐pressure conditions. The degradation behavior is consistent with Fick's law of diffusion. A strong correlation between the degradation rate and relative humidity indicates a mechanism wherein water molecule diffusion governs the degradation process. The film densities of Phen derivatives are calculated using molecular dynamics simulations. High‐density modifier films may physically hinder water diffusion, suppressing degradation. These findings highlight the potential of Phen‐based materials to enable high‐performance organic electronics with efficient electron injection and enhanced stability under minimal encapsulation.