X-Ray Induced Photoconductivity in Anthracene

Abstract

The photoconductivity has been studied in anthracene by irradiation with 50 kV, 0.4 µ sec X-ray pulses. The temperature dependence of hole mobility can be described in terms of a multiple-trapping mechanism; µ h =3.46×102 T -1.1[1+N t /N v exp (Δ ε/k T)]-1, where N t =1.4×1017cm-3 and Δ ε=0.19 eV, while electrons represent µ e =3.6×102 T -1.3, in the range from 316°K to 238°K. The schubweg per unit field is 2.6×10-5cm2/V for holes, while for electrons this value is 1.8×10-5cm2/V at room temperature. The number of collected carriers increases with temperature with the activation energies of 0.02 eV for T≥270°K and of ∼0.06 eV for T<270°K where carrier recombination is predominant. It is shown that in the broad conductivity state wherein electrons have a long mean free path of ≥100Å, the probability for escaping from the attractive coulomb field is more than 4×10-1.