Hole Injection into Molecular Dispersions of 5‘-[4-[Bis(4-ethylphenyl)amino]phenyl]-N,N,N‘,N‘-tetrakis(4-ethylphenyl)-[1,1‘:3‘,1‘‘-terphenyl]-4,4‘‘-diamine

The hole transport properties of 5'-[4-[bis(4-ethylphenyl)amino]phenyl]-N,N,N', [1,1':3',1"-terphenyl]-4,4"-diamine (pEFTP), an aromatic polyamine, have been studied extensively before. We report on the hole injection processes from metal electrodes, or redox solutions, into polymers molecularly doped with pEFTP. By use of the redox couple Fe2+/Fe3+ at large fields, the injection of charges seems to be limiting the current density. At lower fields, competition between recombination and escape processes could be observed in the presence of the reduced form of the redox couple. The influence of the work function of the metals on the values of the dark currents suggests injection controlled currents characterized by almost exclusive hole transport.