Electron transport-related phenomena in organic glasses

The electron transport in low-dielectric disordered solids is the dominant phenomenon associated with the systematic investigations of the effects of ionizing radiation on such media. The mechanism of self-trapping of both positive holes and electrons and the associated distribution, the mobility of self-trapped electrons, the electron trapping by impurities, the conversion of IR electrons to visible ones, and recombination and the Debye-Edwards law have resisted adequate explanations. Alcohols may be unique in their ability to convert IR-absorbing trapped electrons to visible-absorbing ones. At sufficiently high temperature, dipole orientation must be involved, but in glassy state, there is the migration of electrons from shallow to deep traps. The recombination kinetics of trapped isolated charge pairs in glassy solids depends on their initial radical distribution and subsequent charge transport. In the disordered media at cryogenic temperature and in time ranges much less than those required for dielectric relaxation, both hole and electron transport are expected to involve hopping. The prototype system for electron hopping is a heavily doped medium in which shallow electron trapping sites are provided by the impurities. The impurity transport by the first additive will be terminated by the trapping at the second. (Yamashita, S.)