Molecular Interdiffusion between Stacked Layers by Solution and Thermal Annealing Processes in Organic Light Emitting...

Area of Science:

• Materials Science
• Organic Electronics
• Surface Science

Background:

• Interfacial structures significantly impact organic light-emitting diode (OLED) performance.
• Understanding molecular behavior at interfaces is crucial for device optimization.

Purpose of the Study:

• To investigate interdiffusion at polymer-small molecule interfaces in solution-processed and thermally annealed OLEDs.
• To elucidate the relationship between interfacial molecular diffusion and OLED characteristics.

Main Methods:

• Neutron reflectometry was employed to analyze interdiffusion at interfaces.
• Investigated interfaces between polymer underlayers and small molecule overlayers.
• Examined OLEDs subjected to solution processing and thermal annealing.

Main Results:

• Observed asymmetric diffusion: small molecules diffused into the polymer layer, but not vice versa.
• Asymmetric diffusion occurred near the glass transition temperatures of the materials.
• Partial interfacial mixing improved current efficiencies by suppressing triplet-polaron quenching.

Conclusions:

• Interfacial interdiffusion significantly influences OLED performance.
• Controlling and understanding interfacial structures are key to enhancing OLED efficiency.
• Neutron reflectometry is a powerful tool for characterizing such interfaces.