Detrapping of Holes by Singlet Excitons or Photons in Crystalline Anthracene

Hole detrapping has been studied through photoenhanced currents obtained under pulsed illumination of crystalline anthracene. Detrapping by singlet excitons is observed above 260°K, and direct photodetrapping below this temperature. The rate constant for hole detrapping by singlets is ∼10−8 cm3 S−1. No evidence is found of an anomalously large rate constant. The cross section for photodetrapping using photons 4300 < λ < 5500Å is of the order of 10−17 cm2. Hole detrapping and electron detrapping appear to be very similar processes.