ISI Science Citation Index Expanded (by Thomson Reuters Scientific)

The new hole transport materials which comprise molecules consisting of two hydrazone branches linked by a central bridge containing a flexible thiophenyl sulfide and two hydroxyl groups were synthesized and investigated. These transporting materials are low molecular weight glasses and allow preparation of layers stable to crystallization. Ionization potential of the materials is in the range 5.03-5.38 eV. The highest hole mobility, reaching 10-4 cm2/Vs at 6 × 105 V/cm electric field, was observed in the transport material with dimethyltriphenylamine or triphenylamine moieties. These transport materials can be used with or, in the case of a solid substrate, without polymer binder. They can be chemically crosslinked in the layer by reaction of the hydroxyl groups with polyisocyanates.

The synthesis and properties of well defined carbazolyl-containing molecular glasses is reported. They were prepared by the nucleophilic opening of the oxirane ring of 1,3-di(carbazol-9-yl)-2-propanol, 1-(carbazol-9-yl)-3-diphenylamino-2-propanol or 1-(3,6-dibromocarbazol-9-yl)-3-(carbazol-9-yl)-2-propanoI glycidyl ethers with 1,3-benzenediol in the presence of triethylamine. The electrophotographic parameters of undoped films of the molecular glasses and of those doped with difluoroboron-1,3-bis (4-methoxyphenyl)- 1,3-propane dion ate have been studied. The hole drift moblities measured by the time of flight technique in the molecular glasses containing carbazole and diphenylamino groups reach 10(-4) cm(2) V-1 s(-1) at an electric field of 10(6) V cm(-1). The ionization potentials measured by electron photoemission method in air are close to those reported for the other organic photoconductors containing electronically isolated carbazole moieties.

Substituent effects on the hole-drift mobility of N,N,N',N'-tetraarylphenylenediamine derivatives have been investigated. The hole mobility values are dependent on the number of methyl substituents and their position in the investigated transporting materials (TM). The highest mobility was observed in the TM containing methyl groups at the para positions of the side benzene rings and at the central ring. On the other hand, the priority of the m-phenylenediamine derivative against the p-phenylenediamine homologue was proved.