Behavior of the drift mobility in the glass transition region of some hole-transporting amorphous organic films

Drift mobility in prototypical hole-transporting organic glasses is observed to undergo a relatively abrupt, but fully reversible, decrease in activation energy during rate heating near Tg. Sensitivity of charge transport to the dynamic phenomena peculiar to the glass transition process is therefore indicated. No significant hysteresis of the drift mobility is observed during rate heating and subsequent rate cooling through the Tg region. The latter contrasts sharply with the behavior observed in amorphous chalcogenides. It is suggested that absence of mobility hysteresis is a consequence of the fact that electonic states which control transport arise from incorporated chemical species and not, as in the chalcogenides, from structural defects.