Correlation between ionic mobility and luminescent stability in double-layer p–i–n OLED architectures

This study investigates the correlation between ionic mobility and luminescent stability in solution-processed double-layer p–i–n organic light-emitting diode (OLED) architectures. Unlike previous works that emphasized carrier balance through simultaneous annealing, this research focuses on the time-dependent ionic redistribution and its influence on the electro-luminescent degradation behavior. The device structure comprises a photo-crosslinkable hole-transport layer (HTL) and an emissive layer (EML) doped with ionic salts, fabricated via spin-coating under inert atmosphere. Systematic variation of ionic concentration and post-deposition bias-thermal treatment was conducted to analyze ionic mobility using transient current response and impedance spectroscopy. Results show that higher ionic mobility (≈ 10 −7 cm 2 /V s) promotes faster interfacial charge equilibration but accelerates luminance decay due to ion-induced dipolar reorganization within the emissive zone. Conversely, moderate ion mobility enhances charge balance and suppresses exciton quenching, maintaining over 85% of initial luminance after 100 h operation at 37,700 cd/m 2 . The correlation analysis reveals that luminescent stability scales inversely with ionic drift rate, suggesting a critical ionic diffusion threshold for stable electroluminescence. These findings provide new insights into the dynamic interplay between ionic transport and operational stability in solution-processable p–i–n OLEDs, offering a route toward high-efficiency and long-lifetime organic optoelectronic devices.