Photocarrier transport and trapping processes in doped polyethylene terephthalate films

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Abstract
The radiation-induced conductivity of polyethylene terephthalate film is modified by doping this polymer with electron acceptor molecules. Detailed results of x-ray induced thermally stimulated current and photoconductivity experiments are reported for one dopant, 2, 4, 7-trinitro-9-fluorenone. At dopant concentrations≲1019 molecules/cm3, this impurity acts as a deep trap for photocarriers, radically decreasing the radiation-induced conductivity of the doped film. The kinetics of photocarrier trapping in a host material exhibiting dispersive transport is discussed. At dopant concentrations ≳1020 molecules/cm3, the radiation-induced conductivity increases due to the onset of photocarrier transport among the electron acceptor molecules. Utilizing the physical processes discussed in this work, it is possible to develop dielectric materials displaying selected levels of radiation-induced conductivity.