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.phores, the styrene bridge of the dopant chromophore was

We report on a photorefractive polymer with a 4-ms-response time in transient four-wave mixing experiments at 0.5 W/cm2 writing irradiance, 95 V/μm applied electric field, and a grating period of 3.1 μm. Complementary transient ellipsometry, however, reveals orientational birefringence response which leads the four-wave mixing response all the way to its saturation, despite complex dynamics in these processes. Orientation does not limit the dynamic formation of photorefractive gratings in this polymer, which suggests that even faster photorefractive responses are possible for polymer composites with improved charge generation and transport properties.

The optical and photoconductive fatigue of fast photorefractive polymers have been studied in a family of C 60-sensitized polymer composites containing styrene-based chromophores with varying ionization potential. Changes in response time and in photoconductivity were studied for exposures up to 10 4 J/cm 2. Increasing the chromophore ionization potential beyond that of the polyvinylcarbazole host was found to stabilize the response time. Studies of the electric-field dependence of the steady-state diffraction efficiency in various samples confirm the role of C 60 anions as possible traps.