Behavior of the electrical conductivity on melting in an organic semiconductor
Semiconductor-type conduction in solid and liquid organic compounds has been demonstrated by measuring the electrical conductivity over a wide temperature range.
The thermal activation energies agree with those from the long-wave foot of the absorption band for napththalene, anthracene, phenanthrene, and benzanthrone in the solid state. This shows that the first excited singlet state of the molecule is involved in the dark conductivity.
Nitrogen heteroatoms, CH3 groups, and OH groups increase σ at 20 ° C and reduce the activation energy.
The conductivity increases discontinuously on melting; there is a logarithmic relation of γ = σl/σs to melting point for all the compounds examined.
The thermal activation energy is linearly related to the pre-exponential conduction factor for solid and liquid organic compounds whose σ at 20 ° are in the range 10−19 to 10−15 ohm−1 cm−1.
KeywordsActivation Energy Electrical Conductivity Melting Point Anthracene Phenanthrene
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