Posted: October 4, 2006

A single polymer nanowire photodetector

(Nanowerk News) Researchers from the Tyndall National Institute, Ireland, have utilised single conjugated polymer nanowires as ultra-miniature photoconductivity-based photodetectors.
“Semiconducting polymers are attractive materials for opto-electronic applications due to their chemically tunable optical and electronic properties, as well as their facility for low-cost solution processing,” [Gareth Redmond, director of the Nanotechnology group at Tyndall].
"While inorganic semiconductor nanowires and carbon nanotubes have been explored in depth as potential building blocks for nanoscale photonic devices, the challenge of controlled fabrication of 1D nanostructures based on organic molecular materials suitable for integrated (opto)electronic applications has yet to be as comprehensively addressed."
Redmond and colleagues successfully exploited solution-assisted wetting of nanoporous alumina templates for high-yield controlled synthesis of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(bithiophene)] (F8T2) nanowires.
Following liberation from the template and dispersion, their method produces discrete nanowires with average lengths of 15 mm and mean diameters of200 nm. The team also developed electrical contacting strategies for fabrication of two-terminal single polymer nanowire devices on transparent substrates.
"We have found single-nanowire responsivities (current output per unit power of incident light) of approximately 0.4 mAW–1, corresponding to external quantum efficiencies (electrons out per incident photon) of approximately 0.1% under monochromatic light. These values are comparable with data reported for single-inorganic-nanowire devices under similar illumination intensities" said Redmond.
According to Redmond, the nanowires could be building blocks for future nanophotonic devices, including sub-wavelength optical waveguides and emissive devices. "Our demonstration of single nanowire photodetectors is critical to enabling these future applications," he said. Now, the researchers say they will focus their efforts on extending this novel 1-D organic nanostructure approach to demonstration of other key electronic and photonic functionalities.
The researchers reported their work in Advanced Materials (Vol. 18, Issue 18, Page 2379. Cover Article).
Source: Tyndall National Institute
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