Carbon atoms in a conjugated molecule alternate single and double bonds. This overlap of p-orbitals creates a delocalized cloud of π-electrons above and below the molecular plane. It is these π-electrons that are responsible for electronic transport.
Thermal and Structural Properties of the Organic Semiconductor Alq3 and Characterization of Its Excited Electronic Triplet State ( onlinelibrary.wiley.com Marius Grundmann - The Physics of Semiconductors physics of organic semiconductors pdf
: Observed primarily in high-purity single crystals at low temperatures where intermolecular coupling is strong. Carbon atoms in a conjugated molecule alternate single