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Ultrahigh Density Array of Vertically Aligned Small-molecular Organic Nanowires on Arbitrary Substrates
Published on: June 18, 2013
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Directional charge separation in isolated organic semiconductor crystalline nanowires
J A Labastide1, H B Thompson1, S R Marques1
1Department of Chemistry, University of Massachusetts, Amherst Massachusetts 01003, USA.
Nature Communications
|February 26, 2016
Summary
Organic semiconductors can achieve charge separation intrinsically, not just at interfaces. This finding in 7,8,15,16-tetraazaterrylene nanowires challenges conventional organic photovoltaic design principles.
Area of Science:
- Organic electronics
- Materials science
- Photovoltaics
Background:
- Conventional organic photovoltaic (OPV) design relies on interfaces for exciton fission and charge separation.
- Materials engineering efforts focus on nanoscale domain sizes matching exciton diffusion lengths (~10 nm).
Purpose of the Study:
- To investigate intrinsic charge separation mechanisms in organic semiconductors.
- To explore the role of molecular packing in charge generation.
Main Methods:
- Polarized optical excitation of pristine crystalline nanowires of 7,8,15,16-tetraazaterrylene.
- Analysis of photoluminescence decay dynamics along different polarization axes.
Main Results:
- Observed intrinsic generation of charge-separated polaron pairs along the π-stacking direction in nanowires.
- Photoluminescence decay showed power-law behavior along the π-stacking axis, indicating charge separation.
- Transverse photoluminescence decay was exponential, consistent with localized excitons.
Conclusions:
- Intrinsic charge transfer is possible in organic semiconductors, driven by molecular packing.
- This challenges the paradigm requiring interfaces for efficient charge separation in OPVs.
- Molecular packing offers a new avenue for programming charge-transfer interactions in organic electronic devices.
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