Hole transport through chromophores in a photorefractive polymer composite based on poly(N-vinylcarbazole)

The hole mobility, as measured by the linear time-of-flight technique, is higher than expected at (2±0.5)×10−6 cm2 (V s)−1 at an applied field of 50 V μm−1 in a photorefractive polymer composite. The components were poly(N-vinylcarbazole), the electro-optic chromophore 1-(2′-ethylhexyloxy)-2,5,dimethyl-4-(4′′nitrophenylazo)benzene together with sensitisor 2,4,7-trinitro-9-fluorenone. This mobility is unchanged within experimental accuracy after the replacement of the poly(N-vinylcarbazole) by the dielectric polycarbonate. Polycarbonate in pure form without the chromophores is an insulator. We conclude that hole transport in the photorefractive composite occurs through the network of chromophores and not through the charge-transport polymer.