We report on a photorefractive polymer composite that shows an initial rise time of 4 ms at a grating spacing of 3.1 μm. A systematic characterization of the ionization potential of a series of chromophores used in photorefractive applications is presented. No obvious correlation between material response time and ionization potential is found in PVK:ECZ:TNFDM composites doped with chromophores with an ionization potential higher or comparable to that of carbazole. All the chromophores under investigation are found to form a charge-transfer complex with the sensitizer TNFDM and a correlation between the spectral position of this band and the value of the ionization potential of the chromophore is demonstrated.