Electroabsorption of Photoconductive Azo Pigments

Abstract
Photoexcited states of fluorenone bisazo and triphenylamine trisazo pigments, both generating photocarriers extrinsically with the hole-transport-type arylamine molecules through the photoinduced electron transfer with high efficiency, were investigated by means of electromodulated absorption spectra. As a result, it was found that the former pigment forms a Frenkel exciton and the latter pigment a charge-transfer (CT) exciton. The different types of excitons well explained the photosensitivity of photoreceptors based on these two azo pigments.