Measurement of Contact Potential Difference for Organic Crystals. Work Function of Violanthrene

A vibrating-reed type cell for measuring contact potential difference was constructed and successfully applied for organic crystals. From the observed contact potential difference for violanthrene against graphite, the work function has been estimated as 4.50±0.1 eV. In association with the activation energy for electrical conductivity, 0.8–0.9 eV, the electronic energy diagram for violanthrene has been illustrated, which revealed the extrinsic nature of semiconduction and the energy gap, 2.3–2.5 eV, being comparable with the first excited singlet state of violanthrene molecule.