Photoconductive properties of PVK-based photorefractive polymer compositesdoped with fluorinated styrene chromophores

We have synthesized nine anisotropic chromophores, with different degrees o f fluorination, and studied the effect of the chromophore's ionization pote ntial on charge-transfer complexation, photoconductivity, and response time in photorefractive polymer mixtures based on poly(vinylcarbazole). (2,4,7- Trinitrofluoren-9-ylidene)malononitrile (TNFDM) or C-60 provided the sensit ization. We have found evidence of strong complexation between TNFDM and th e chromophore. At high electric fields, the photoconductivity decays during illumination and reaches a limiting value that correlates with the chromop hore's ionization potential. A buildup of C-60(-) radical anions is observe d simultaneously. The strong decline in photoconductivity correlates with a n increase in the photorefractive grating buildup time.