Sensitization of Photoconductivity. Poly-N-vinylcarbazole with the Copolymerized Dye Molecule

The sensitization of the photoconductivity of PVCz by dyes was investigated by the measurement of the characteristics of the decay of the surface charge put on the polymer films. MG was selected as a dye and the following three systems were measured and the degree of the sensitization was compared; i. e., PVCz-MG, copolymer of VGz and VMG and PVCz-PVMG systems. The sensitization was observed in the wavelength region from 300 to 1200 mμ. Sensitization in the visible region was larger than in the ultraviolet. The copolymer system was inferior to the PVGz-MG system, probably because of the large loss of the carriers by the recombination and trapping in the bulk. There was the optimum concentration of the dyecontent, probably because of the disturbing effect of the dye molecule for the migration of the carriers. To make sure this point, the inhomogeneous films with the dye only on the surface were investigated. The results were explained by the difference in the distiribution of the centers of carrier generation and those of recombination and trapping of the carriers in the bulk.