HOUSTON (Feb. 27, 2013) Researchers at Rice University and Sandia National Laboratories have made a nanotube-based photodetector that gathers light in and beyond visible wavelengths. It promises to make possible a unique set of optoelectronic devices, solar cells and perhaps even specialized cameras.
A traditional camera is a light detector that captures a record, in chemicals, of what it sees. Modern digital cameras replaced film with semiconductor-based detectors.
But the Rice detector, the focus of a paper that appeared today in the online Nature journal Scientific Reports, is based on extra-long carbon nanotubes. At 300 micrometers, the nanotubes are still only about 100th of an inch long, but each tube is thousands of times longer than it is wide.
That boots the broadband detector into what Rice physicist Junichiro Kono considers a macroscopic device, easily attached to electrodes for testing. The nanotubes are grown as a very thin "carpet" by the lab of Rice chemist Robert Hauge and pressed horizontally to turn them into a thin sheet of hundreds of thousands of well-aligned tubes.
They're all the same length, Kono said, but the nanotubes have different widths and are a mix of conductors and semiconductors, each of which is sensitive to different wavelengths of light. "Earlier devices were either a single nanotube, which are sensitive to only limited wavelengths," he said. "Or they were random networks of nanotubes that worked, but it was very difficult to understand why."
"Our device combines the two techniques," said Sbastien Nanot, a former postdoctoral researcher in Kono's group and first author of the paper. "It's simple in the sense that each nanotube is connected to both electrodes, like in the single-nanotube experiments. But we have many nanotubes, which gives us the quality of a macroscopic device."
With so many nanotubes of so many types, the array can detect light from the
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