We report on photoelectric and holographic investigations of an organic photorefractive material based on a low molar mass glass with both photoconductive and nonlinear optical properties. By implementing a suitable plasticizer we obtained a composite system which shows extremely fast initial response times down to 450 mu s at writing beam intensities of I-write = 10.8 W/cm(2) and 2.5 ms at the canonical intensity of I-write = 1 W/cm(2). Furthermore, high refractive index modulations up to Delta n = 6.1 x 10(-3), long lifetimes and high optical quality of the samples are observed. In comparison to a second similar composite system, which was plasticized by a more polar dopand, we demonstrate the crucial role of this functional constituent on the photoelectric properties. Time-of-flight measurements show a major impact of the plasticizer on the dispersivity of charge-carrier transport. Subsequently the buildup and decay dynamics of the photorefractive grating are Substantially affected. Holographic time-of-flight measurements confirm these observations.