Carbazole charge-transporting molecules

The first photorefractive sol-gel film was prepared by copolymerization of TEOS and modified silane monomers [285]. Photorefractive sol-gel materials that contain a second-order nonlinear chromophore and carbazole charge-transporting molecules both covalently attached to the silica-based backbone were also reported [286,287]. 

Conceptually similar are single-layer photoreceptors such as PVK filled with a photoconductive pigment, such as IV,IV-di(3,5-dimethylphenyl)perylene-3,4,9,10-tetracarboxylic acid diimi.de (32), or a photoconductor containing a bisazo photoconductive pigment, a hole transporting molecule such as an indolinyl hydrazone derivative of carbazole shown in Fig. 5i, in a polyester binder (33). In practice, this photoconductor is charged positively even though both holes and electrons are mobile. 

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