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Spatially resolved electrostatic potential and photocurrent generation in carbon nanotube array devices
Michael Engel1, Mathias Steiner, Ravi S Sundaram
1Institute of Nanotechnology, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.
ACS Nano
|July 10, 2012
Summary
Laser-excited photocurrent microscopy maps electrostatic potential in semiconducting single-walled carbon nanotube (S-SWCNT) devices, revealing performance bottlenecks and enabling optimized photovoltaic designs.
Area of Science:
- Materials Science and Engineering
- Nanotechnology
- Solid-State Physics
Background:
- Understanding the electrostatic potential within semiconducting single-walled carbon nanotube (S-SWCNT) devices is crucial for optimizing their performance.
- Existing imaging techniques often lack the resolution to identify local heterogeneities that limit device operation.
- Photocurrent microscopy offers a potential avenue for probing these internal potentials with high spatial resolution.
Purpose of the Study:
- To map the internal electrostatic potential profile of S-SWCNT array devices using laser-excited photocurrent microscopy.
- To identify performance-limiting local heterogeneities in the electrostatic potential.
- To enable direct measurement of charge carrier transfer lengths at S-SWCNT-metal interfaces and formulate design rules for S-SWCNT-based photovoltaic devices.
Main Methods:
- Utilized laser-excited photocurrent microscopy with a spatial resolution of 250 nm to map electrostatic potential profiles.
- Performed measurements on S-SWCNTs integrated into optically transparent samples.
- Acquired photocurrent images from the underside of S-SWCNT-metal contacts to measure charge carrier transfer lengths.
Main Results:
- Successfully mapped the internal electrostatic potential profile of S-SWCNT array devices.
- Identified previously unobservable local heterogeneities in the electrostatic potential that impact device performance.
- Enabled direct measurement of charge carrier transfer lengths at palladium-S-SWCNT and aluminum-S-SWCNT interfaces.
- Demonstrated external control of the electrostatic potential profile using local metal gates.
Conclusions:
- Laser-excited photocurrent microscopy provides critical insights into S-SWCNT device physics and operation.
- The technique reveals performance-limiting heterogeneities, guiding the development of improved S-SWCNT-based photovoltaic devices.
- The ability to control the electrostatic potential offers new avenues for device engineering and optimization.
