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Quantifying resistances across nanoscale low- and high-angle interspherulite boundaries in solution-processed organic
Stephanie S Lee1, Jeffrey M Mativetsky, Marsha A Loth
1Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.
ACS Nano
|October 2, 2012
Summary
Inter-spherulite boundaries (ISBs) in organic semiconductors impede charge transport. High-angle ISBs significantly disrupt current flow, unlike low-angle ISBs, impacting device performance.
Area of Science:
- Materials Science
- Organic Electronics
- Solid-State Physics
Background:
- Polycrystalline organic semiconductor thin films exhibit reduced charge transport due to nanoscale boundaries between spherulites.
- These interspherulite boundaries (ISBs) present complex structural variations in molecular orientation mismatch.
- Understanding the impact of ISB characteristics on charge transport is crucial for improving organic electronic devices.
Purpose of the Study:
- To investigate how the angle of molecular orientation mismatch at interspherulite boundaries (ISBs) influences their electrical resistivity.
- To differentiate the charge transport behavior across low-angle versus high-angle ISBs in solution-processed organic semiconductor thin films.
Main Methods:
- Fabrication of triethylsilylethynyl anthradithiophene thin films with exclusively low-angle and high-angle ISBs.
- Utilizing conductive Atomic Force Microscopy (c-AFM) to probe local conductivity.
- Employing four-probe measurements to quantify charge transport properties across ISBs.
Main Results:
- Current flow is unhindered across low-angle ISBs.
- High-angle ISBs significantly impede current flow, with an estimated resistivity of 22 MΩμm(2)/width.
- The resistivity across high-angle ISBs is substantially higher than low-angle grain boundaries in thermally evaporated films.
Conclusions:
- The angle of molecular orientation mismatch at ISBs critically affects charge transport in organic semiconductor thin films.
- High-angle ISBs act as significant barriers to charge carriers, limiting device mobility.
- Differences in film formation processes between solution-processed and thermally evaporated organic semiconductors contribute to varying boundary resistivities.
