Extremely Efficient Multiple Electron-Hole Pair Generation in Carbon Nanotube Photodiodes

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Science  11 Sep 2009:
Vol. 325, Issue 5946, pp. 1367-1371
DOI: 10.1126/science.1176112

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We observed highly efficient generation of electron-hole pairs due to impact excitation in single-walled carbon nanotube p-n junction photodiodes. Optical excitation into the second electronic subband E22 leads to striking photocurrent steps in the device I-VSD characteristics that occur at voltage intervals of the band-gap energy EGAP/e. Spatially and spectrally resolved photocurrent combined with temperature-dependent studies suggest that these steps result from efficient generation of multiple electron-hole pairs from a single hot E22 carrier. This process is both of fundamental interest and relevant for applications in future ultra-efficient photovoltaic devices.

  • Present address: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA.

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