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Orientation-Dependent Work-Function Modification Using Substituted Pyrene-Based Acceptors
O T Hofmann1, H Glowatzki2, C Bürker3
1Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
The Journal of Physical Chemistry. C, Nanomaterials and Interfaces
|November 21, 2017
Summary
Molecular acceptors like pyrene-tetraone tune metal electrode work functions, impacting organic semiconductor charge injection. Adsorbate structure, not just electron affinity, significantly alters electronic properties.
Area of Science:
- Surface science
- Materials science
- Organic electronics
Background:
- Work function tuning is crucial for organic electronics.
- Molecular acceptors can modify electrode properties.
- Understanding adsorption effects is key for device performance.
Purpose of the Study:
- Investigate pyrene-tetraone derivatives (PyT, Br-PyT, NO2-PyT) for modifying Au(111) and Ag(111) work functions.
- Explore the impact of molecular electron affinity and adsorbate structure on electrode electronic properties.
- Explain deviations from expected Fermi-level pinning trends.
Main Methods:
- Complementary theoretical and experimental approaches.
- Photoelectron spectroscopy.
- X-ray standing wave technique.
- Density functional theory simulations.
Main Results:
- Observed Fermi-level pinning trends for some interfaces.
- Significant deviations for Br-PyT/Ag(111) and NO2-PyT/Ag(111), with a 1.6 eV work function increase for NO2-PyT/Ag(111).
- Adsorption-induced molecular reorientation (face-on to edge-on) explains deviations.
- Edge-on orientation leads to larger work function changes.
Conclusions:
- Molecular orientation significantly impacts electrode electronic properties, beyond electron affinity.
- Adsorbate structure is a critical factor in work function modification.
- Provides comprehensive understanding for designing organic electronic devices.
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