Single polymer nanowire detects light

04 Oct 2006

Photodetectors based on single polymer nanowires could form building blocks for nanophotonic devices.

Researchers from the Tyndall National Institute and the University of Limerick, both in Ireland, have used single polymer nanowires as photoconductivity-based photodetectors. They made the nanowires by solution-assisted template wetting.

"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 told nanotechweb.org.

"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 one-dimensional nanostructures based on organic molecular materials has yet to be as comprehensively addressed for integrated (opto)electronic applications."

Redmond and colleagues exploited solution-assisted wetting of nanoporous alumina templates for high-yield synthesis of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(bithiophene)] (F8T2) nanowires. Following liberation of the nanowires from the template and dispersion, the method produced discrete nanowires with average lengths of 15 µm and mean diameters of 200 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," said Redmond. "These values are comparable with data reported for single inorganic nanowire devices under similar illumination intensities."

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 one-dimensional organic nanostructure approach to demonstration of other key electronic and photonic functionalities. The researchers reported their work in Advanced Materials.