Investigating degradation mechanisms in organic light-emitting diodes using operando electrically pumped spectroscopy

Area of Science:

• Materials Science
• Organic Electronics
• Spectroscopy

Background:

• Organic light-emitting diodes (OLEDs) are crucial for displays and lighting.
• Understanding OLED degradation is key to improving device stability and lifespan.
• Conventional diagnostics like impedance spectroscopy (IS) offer limited insight into microscopic failure mechanisms.

Purpose of the Study:

• To comprehensively analyze OLED degradation by integrating IS with operando electrically pumped spectroscopy (EPS).
• To identify specific layers and interfaces responsible for efficiency loss in degraded OLEDs.
• To elucidate the role of exciton dynamics in thermal degradation pathways.

Main Methods:

• Simultaneous electrical and optical probing of OLED devices under operational bias using integrated IS and EPS.
• Investigation of both in-situ and ex-situ fabricated OLED samples under pristine and thermally degraded conditions.
• Analysis of single-layer and bilayer films, kinetic modeling, and decay-associated spectral analysis.

Main Results:

• IS captured electrical trends but failed to localize degradation.
• EPS revealed dominant exciton scattering and energy transfer disruptions at the emissive layer (EML) and EML/hole transport layer (HTL) interface.
• Ultrafast exciton quenching pathways induced by thermal stress were identified.

Conclusions:

• EPS is a powerful diagnostic tool for visualizing exciton dynamics and localizing degradation in OLEDs.
• The findings provide critical insights for designing more stable OLED device architectures.
• This integrated approach overcomes limitations of conventional electrical diagnostics for OLED failure analysis.