Carbon-nanotube optoelectronics

Semiconducting single-walled carbon nanotubes are direct-gap materials that provide ideal systems for the study of photophysics in one-dimension. While their excited states involve strongly bound 1D excitons, their single atomic layer structure makes their optical properties especially sensitive to their environment and external fields, thus allowing for their controlled modification. In this chapter we review the properties of the excited states of nanotubes, the mechanisms of their production and detection, focusing particularly on electrically-induced excitation by ambipolar electron-hole recombination and impact excitation by hot carriers. Radiative decay of photo-excited and electron-excited (electroluminescence) emission as well as the non-radiative decay to free carriers leading to photoconductivity are discussed. The influence of external electric fields and of environmental interactions on excited nanotubes is considered. Finally, the possible technological uses of carbon nanotubes as nanometer scale light sources and photocurrent and photovoltage detectors are discussed.