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

Abstract

We have synthesized nine anisotropic chromophores, with different degrees of fluorination, and studied the effect of the chromophore's ionization potential 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 sensitization. We have found evidence of strong complexation between TNFDM and the chromophore. At high electric fields, the photoconductivity decays during illumination and reaches a limiting value that correlates with the chromophore's ionization potential. A buildup of C ₆₀ ^– radical anions is observed simultaneously. The strong decline in photoconductivity correlates with an increase in the photorefractive grating buildup time.