Anomalous Transition in Charge Transport Behavior of Polysilane

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Anomalous transition of the dispersion parameter α was observed for the first time in poly (n-butyl-n-pentylsilane) (PBPS). Time-of-flight photocurrent (I) of PBPS was measured. The photocurrent transient was dispersive: I∞t^<-(1-α)>. The dispersion parameter a dropped around the glass transition temperature T_g with increasing temperature, and became temperature-independent above T_g. The mobility was described within the framework of a formalism based on disorder due to Bassler and coworkers. Both the diagonal disorder parameter σ, the variance of the density of states, and the off-diagonal disorder parameter Σ, the degree of positional disorder, decreased around T_g. Nevertheless the ratio of the off-diagonal disorder parameter Σ to the diagonal disorder parameter σ was found to increase above the transition temperature. This anomalous transition is rationalized by the assumption that the off-diagonal disorder dominates charge transport in PBPS above T_g.
社団法人応用物理学会の論文
1995-07-30