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Diffusion in Organic Film Stacks Containing Solution-Processed Phosphorescent Poly(dendrimer) Dopants
Jake A McEwan1, Andrew J Clulow1, Andrew Nelson2
1Centre for Organic Photonics & Electronics, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia.
ACS Applied Materials & Interfaces
|June 25, 2021
Summary
The distribution of materials in organic light-emitting diodes (OLEDs) affects efficiency. Thermal annealing caused intermixing, decreasing photoluminescence and highlighting the importance of material stability for OLED durability.
Area of Science:
- Materials Science
- Organic Electronics
- Nanotechnology
Background:
- Efficient organic light-emitting diodes (OLEDs) rely on emissive layers with guest-host blends and charge transport layers.
- Understanding material distribution and thermal behavior is crucial for OLED stability and efficiency.
Purpose of the Study:
- Investigate the film structures of emissive layers in phosphorescent poly(dendrimer)/4,4'-N,N'-di(carbazolyl)biphenyl blends.
- Analyze the impact of thermal annealing on material distribution and photoluminescence.
Main Methods:
- Combined neutron reflectometry and photoluminescence measurements.
- Studied films comprising emissive layers with phosphorescent poly(dendrimer) and a host material.
- Examined structural changes upon thermal annealing.
Main Results:
- The emissive poly(dendrimer) showed a concentration gradient, not uniform distribution, within the host.
- Thermal annealing led to intermixing between the emissive and electron transport layers.
- Intermixing decreased poly(dendrimer) photoluminescence, attributed to increased interchromophore interactions or aggregation.
Conclusions:
- Uniform guest-host mixing is not strictly essential for OLED efficiency.
- Thermal stability of host and charge transport materials is critical for device durability.
- Material distribution and thermal behavior significantly influence OLED performance and longevity.
