Controlled p-type doping of polycrystalline and amorphous organic layers: Self-consistent description of conductivity and field-effect mobility by a microscopic percolation model - art. no. 195208

We present a systematic study on p-type doping of zinc-phthalocyanine by te trafluoro-tetracyanoquinodimethane as an example of controlled doping of th in organic films by cosublimation of matrix and dopant. The zinc-phthalocya nine layers are prepared both in polycrystalline and amorphous phase by var iation of the sublimation conditions. The films are electrically characteri zed in situ by temperature dependent conductivity and Seebeck and field-eff ect measurements. In addition to previous work, we show that also amorphous phthalocyanine layers can be doped, i.e., their conductivity increases and their Seebeck coefficient decreases indicating a shift of the Fermi level towards the hole transport level. The field-effect mobility of the polycrys talline samples is in the range of 10(-4)-10(-3) cm(-2)/Vs and increases wi th increasing dopant concentration. Adapting a percolation model presented by Vissenberg and Matters [Phys. Rev. B, 57, 12 964 (1998)], which assumes hopping transport within a distribution of localized states, we can quantit atively describe the conductivity (in different organic layers) and the fie ld-effect mobility.