Photoconductivity in single wall carbon nanotube sheets

In this paper we report for the first time, the photoconductivity of large area sheets of single wall carbon nanotube upon laser illumination. The photoconductivity exhibited an increase, decrease or even 'negative' values when the laser spot was on different positions between contact electrodes, showing a 'position' dependent effect of photoconductivity. Photon induced charge carrier generation in single wall carbon nanotubes and subsequent charge separation across the metal-carbon nanotube contacts is believed to cause the photoconductivity changes. A net photovoltage of similar to 10 mV and a photocurrent of similar to 1.6 mA were produced under the laser intensity of similar to 160 mW with a quantum efficiency of similar to 1.5% in vacuum. The effect of the contact area between the electrodes and nanotubes, ambient pressure, laser intensity and light pulse frequency on the photoconductivity is discussed.