Influence of the chromophore ionization potential on speed and magnitude of photorefractive effects in poly(N-vinylcarbazole) based polymer composites

We report on the synthesis of three highly polar chromophores and their use as dopants in poly(N-vinylcarbazole) based photorefractive polymer composi tes sensitized with (2,4,7-trinitro-9-fluorenylidene)malononitrile. Small a lterations in the amino donor group substituents were used to tune the dye' s ionization potential (IP) by 0.2 eV. At 780 nm, 5 degrees C above the gla ss transition temperature (T-g), and with an applied field of 59 V/mu m, we observed complete internal diffraction and a gain coefficient of 167 cm(-1 ). In this temperature range, diffraction efficiency, gain coefficient, and photorefractive phase shift were found to correlate with the chromophore I P. At 20 degrees C below Tg, the contribution from birefringence to the ind ex modulation is insignificant, and the speed of the photorefractive effect correlates well with the chromophore IP. Analysis of the results suggests that the space-charge field is influenced by the chromophore IP. (C) 2000 A merican Institute of Physics. [S0021-9606(00)70224-8].