Charge transport arylamines

For hole transport, many of the first materials used in OLEDs were originally developed for use in xerography. Various models have been proposed to describe charge transport in such materials [75,76]. One of the most common classes of material used is the arylamines,... 

Among arylamine semiconductors, indolo[3,2-ib]carbazole (5) is an appealing system for studies because it has a relatively large and planar molecular structure to enable facile establishment of higher structural order for charge transport [57, 58]. Earlier, we reported the use of 5,ll-bis(l-naphthyl)indolo[3,2-jb]carbazole, a derivative of 5, as a hole transport material in OLEDs [59]. Because of its sterically encumbered naphthyl substituents, this compound forms only an amorphous film on vacuum deposition, and mobility is low in OTFTs, as expected. 

Polymers with aromatic amine groups (and various substituents) comprise the most studied and best understood photoconductive and charge-transporting materials (Fig. 8.13). The arylamine transport-active groups are either part of the polymer structure or are mixed with the host polymer. One can easily recognize that PVK is a substituted aromatic amine. 

As mentioned above, most of the discussed photoconduetive polymers are p-type photoconductors. Even in those cases where the charge carriers were not identified, it is safe to assume that the majority carriers are holes. All polynuclear aromatic and arylamine polymers are basically electron donors and therefore the transport involves equilibria between the neutral monomer units and positively... 

Hole transport in polymers occurs by charge transfer between adjacent donor functionalities. The functionalities can be associated with a dopant molecule, pendant groups of a polymer, or the polymer main chain. Most literature references are of doped polymers. The more common donor molecules include various arylalkane, arylamine, enamine, hydrazone, oxadiazole, oxazole, and pyrazoline derivatives. Commonly used polymers are polycarbonates, polyesters, and poly(styrene)s. Transport processes in these materials are unipolar. The mobilities are very low, strongly field and temperature dependent, as well as dependent on the dopant molecule, dopant concentration, and the polymer host This chapter reviews hole transport in polymers and doped polymers of potential relevance to xerography. The organization is by chemical classification. The discussion mainly includes molecularly doped, pendant, and... 

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